Reduce the proliferation of VMEXIT_RESTART in task_switch.c.
This is in preparation for further simplification of the return values from VM exit handlers in bhyve(8).
This commit is contained in:
Neel Natu
parent
d37f2adb38
commit
e84d8ebfcc
@ -47,15 +47,6 @@ __FBSDID("$FreeBSD$");
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#include "bhyverun.h"
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/*
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* Various functions in this file use 0 to denote success and VMEXIT_ABORT
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* or VMEXIT_RESTART to denote failure. This assumes that the VMEXIT_xyz
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* macros expand to non-zero values. Enforce this with a compile-time
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* assertion.
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*/
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CTASSERT(VMEXIT_ABORT != 0);
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CTASSERT(VMEXIT_RESTART != 0);
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/*
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* Using 'struct i386tss' is tempting but causes myriad sign extension
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* issues because all of its fields are defined as signed integers.
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@ -175,6 +166,10 @@ sel_exception(struct vmctx *ctx, int vcpu, int vector, uint16_t sel, int ext)
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vm_inject_fault(ctx, vcpu, vector, 1, sel);
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}
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/*
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* Return 0 if the selector 'sel' in within the limits of the GDT/LDT
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* and non-zero otherwise.
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*/
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static int
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desc_table_limit_check(struct vmctx *ctx, int vcpu, uint16_t sel)
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{
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@ -197,6 +192,14 @@ desc_table_limit_check(struct vmctx *ctx, int vcpu, uint16_t sel)
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return (0);
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}
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/*
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* Read/write the segment descriptor 'desc' into the GDT/LDT slot referenced
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* by the selector 'sel'.
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*
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* Returns 0 on success.
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* Returns 1 if an exception was injected into the guest.
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* Returns -1 otherwise.
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*/
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static int
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desc_table_rw(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging,
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uint16_t sel, struct user_segment_descriptor *desc, bool doread)
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@ -236,6 +239,13 @@ desc_table_write(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging,
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return (desc_table_rw(ctx, vcpu, paging, sel, desc, false));
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}
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/*
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* Read the TSS descriptor referenced by 'sel' into 'desc'.
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*
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* Returns 0 on success.
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* Returns 1 if an exception was injected into the guest.
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* Returns -1 otherwise.
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*/
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static int
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read_tss_descriptor(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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uint16_t sel, struct user_segment_descriptor *desc)
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@ -252,18 +262,13 @@ read_tss_descriptor(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
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else
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sel_exception(ctx, vcpu, IDT_GP, sel, ts->ext);
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return (VMEXIT_RESTART);
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return (1);
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}
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sup_paging = ts->paging;
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sup_paging.cpl = 0; /* implicit supervisor mode */
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error = desc_table_read(ctx, vcpu, &sup_paging, sel, desc);
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if (error < 0)
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return (VMEXIT_ABORT);
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else if (error > 0)
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return (VMEXIT_RESTART);
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else
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return (0);
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return (error);
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}
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static bool
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@ -294,6 +299,13 @@ ldt_desc(int sd_type)
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return (sd_type == SDT_SYSLDT);
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}
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/*
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* Validate the descriptor 'seg_desc' associated with 'segment'.
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*
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* Returns 0 on success.
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* Returns 1 if an exception was injected into the guest.
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* Returns -1 otherwise.
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*/
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static int
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validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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int segment, struct seg_desc *seg_desc)
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@ -332,13 +344,13 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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/* LDT selector must point into the GDT */
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if (ldtseg && ISLDT(sel)) {
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sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
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return (VMEXIT_RESTART);
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return (1);
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}
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/* Descriptor table limit check */
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if (desc_table_limit_check(ctx, vcpu, sel)) {
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sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
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return (VMEXIT_RESTART);
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return (1);
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}
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/* NULL selector */
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@ -346,7 +358,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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/* Code and stack segment selectors cannot be NULL */
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if (codeseg || stackseg) {
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sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
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return (VMEXIT_RESTART);
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return (1);
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}
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seg_desc->base = 0;
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seg_desc->limit = 0;
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@ -358,10 +370,8 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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sup_paging = ts->paging;
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sup_paging.cpl = 0; /* implicit supervisor mode */
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error = desc_table_read(ctx, vcpu, &sup_paging, sel, &usd);
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if (error < 0)
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return (VMEXIT_ABORT);
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else if (error > 0)
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return (VMEXIT_RESTART);
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if (error)
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return (error);
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/* Verify that the descriptor type is compatible with the segment */
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if ((ldtseg && !ldt_desc(usd.sd_type)) ||
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@ -369,7 +379,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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(dataseg && !data_desc(usd.sd_type)) ||
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(stackseg && !stack_desc(usd.sd_type))) {
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sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
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return (VMEXIT_RESTART);
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return (1);
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}
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/* Segment must be marked present */
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@ -381,7 +391,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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else
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idtvec = IDT_NP;
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sel_exception(ctx, vcpu, idtvec, sel, ts->ext);
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return (VMEXIT_RESTART);
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return (1);
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}
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cs = GETREG(ctx, vcpu, VM_REG_GUEST_CS);
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@ -391,7 +401,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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if (stackseg && (rpl != cpl || dpl != cpl)) {
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sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
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return (VMEXIT_RESTART);
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return (1);
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}
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if (codeseg) {
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@ -399,7 +409,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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if ((conforming && (cpl < dpl)) ||
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(!conforming && (cpl != dpl))) {
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sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
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return (VMEXIT_RESTART);
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return (1);
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}
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}
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@ -415,7 +425,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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if (!conforming && (rpl > dpl || cpl > dpl)) {
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sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
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return (VMEXIT_RESTART);
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return (1);
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}
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}
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*seg_desc = usd_to_seg_desc(&usd);
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@ -464,6 +474,13 @@ update_seg_desc(struct vmctx *ctx, int vcpu, int reg, struct seg_desc *sd)
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assert(error == 0);
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}
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/*
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* Update the vcpu registers to reflect the state of the new task.
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*
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* Returns 0 on success.
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* Returns 1 if an exception was injected into the guest.
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* Returns -1 otherwise.
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*/
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static int
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tss32_restore(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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uint16_t ot_sel, struct tss32 *tss, struct iovec *iov)
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@ -506,7 +523,7 @@ tss32_restore(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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reserved = ~maxphyaddr | 0x1E6;
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if (pdpte[i] & reserved) {
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vm_inject_gp(ctx, vcpu);
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return (VMEXIT_RESTART);
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return (1);
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}
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}
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SETREG(ctx, vcpu, VM_REG_GUEST_PDPTE0, pdpte[0]);
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@ -595,6 +612,15 @@ tss32_restore(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
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return (0);
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}
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/*
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* Push an error code on the stack of the new task. This is needed if the
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* task switch was triggered by a hardware exception that causes an error
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* code to be saved (e.g. #PF).
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*
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* Returns 0 on success.
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* Returns 1 if an exception was injected into the guest.
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* Returns -1 otherwise.
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*/
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static int
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push_errcode(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging,
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int task_type, uint32_t errcode)
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@ -640,26 +666,40 @@ push_errcode(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging,
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if (vie_calculate_gla(paging->cpu_mode, VM_REG_GUEST_SS,
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&seg_desc, esp, bytes, stacksize, PROT_WRITE, &gla)) {
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sel_exception(ctx, vcpu, IDT_SS, stacksel, 1);
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return (VMEXIT_RESTART);
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return (1);
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}
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if (vie_alignment_check(paging->cpl, bytes, cr0, rflags, gla)) {
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vm_inject_ac(ctx, vcpu, 1);
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return (VMEXIT_RESTART);
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return (1);
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}
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error = vm_copy_setup(ctx, vcpu, paging, gla, bytes, PROT_WRITE,
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iov, nitems(iov));
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assert(error == 0 || error == 1 || error == -1);
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if (error) {
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return ((error == 1) ? VMEXIT_RESTART : VMEXIT_ABORT);
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}
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if (error)
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return (error);
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vm_copyout(ctx, vcpu, &errcode, iov, bytes);
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SETREG(ctx, vcpu, VM_REG_GUEST_RSP, esp);
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return (0);
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}
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/*
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* Evaluate return value from helper functions and potentially return to
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* the VM run loop.
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* 0: success
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* +1: an exception was injected into the guest vcpu
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* -1: unrecoverable/programming error
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*/
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#define CHKERR(x) \
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do { \
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assert(((x) == 0) || ((x) == 1) || ((x) == -1)); \
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if ((x) == -1) \
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return (VMEXIT_ABORT); \
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else if ((x) == 1) \
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return (VMEXIT_CONTINUE); \
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} while (0)
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int
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vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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{
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@ -695,8 +735,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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/* Fetch the new TSS descriptor */
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error = read_tss_descriptor(ctx, vcpu, task_switch, nt_sel, &nt_desc);
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if (error)
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return (error);
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CHKERR(error);
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nt = usd_to_seg_desc(&nt_desc);
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@ -705,13 +744,13 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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if (nt_type != SDT_SYS386BSY && nt_type != SDT_SYS386TSS &&
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nt_type != SDT_SYS286BSY && nt_type != SDT_SYS286TSS) {
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sel_exception(ctx, vcpu, IDT_TS, nt_sel, ext);
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return (VMEXIT_RESTART);
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goto done;
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}
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/* TSS descriptor must have present bit set */
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if (!SEG_DESC_PRESENT(nt.access)) {
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sel_exception(ctx, vcpu, IDT_NP, nt_sel, ext);
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return (VMEXIT_RESTART);
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goto done;
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}
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/*
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@ -728,13 +767,13 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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assert(minlimit > 0);
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if (nt.limit < minlimit) {
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sel_exception(ctx, vcpu, IDT_TS, nt_sel, ext);
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return (VMEXIT_RESTART);
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goto done;
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}
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/* TSS must be busy if task switch is due to IRET */
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if (reason == TSR_IRET && !TSS_BUSY(nt_type)) {
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sel_exception(ctx, vcpu, IDT_TS, nt_sel, ext);
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return (VMEXIT_RESTART);
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goto done;
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}
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/*
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@ -743,21 +782,14 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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*/
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if (reason != TSR_IRET && TSS_BUSY(nt_type)) {
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sel_exception(ctx, vcpu, IDT_GP, nt_sel, ext);
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return (VMEXIT_RESTART);
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goto done;
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}
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/* Fetch the new TSS */
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error = vm_copy_setup(ctx, vcpu, &sup_paging, nt.base, minlimit + 1,
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PROT_READ | PROT_WRITE, nt_iov, nitems(nt_iov));
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if (error == 1) {
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/* Restart vcpu execution to handle the page fault */
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return (VMEXIT_RESTART);
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} else if (error == -1) {
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return (VMEXIT_ABORT);
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} else {
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assert(error == 0);
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vm_copyin(ctx, vcpu, nt_iov, &newtss, minlimit + 1);
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}
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CHKERR(error);
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vm_copyin(ctx, vcpu, nt_iov, &newtss, minlimit + 1);
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/* Get the old TSS selector from the guest's task register */
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ot_sel = GETREG(ctx, vcpu, VM_REG_GUEST_TR);
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@ -769,7 +801,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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* (sel = 0, base = 0, limit = 0xffff).
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*/
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sel_exception(ctx, vcpu, IDT_TS, ot_sel, task_switch->ext);
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return (VMEXIT_RESTART);
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goto done;
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}
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/* Get the old TSS base and limit from the guest's task register */
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@ -781,24 +813,14 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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assert(ot_type == SDT_SYS386BSY || ot_type == SDT_SYS286BSY);
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/* Fetch the old TSS descriptor */
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error = read_tss_descriptor(ctx, vcpu, task_switch, ot_sel,
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&ot_desc);
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if (error)
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return (error);
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error = read_tss_descriptor(ctx, vcpu, task_switch, ot_sel, &ot_desc);
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CHKERR(error);
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/* Get the old TSS */
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error = vm_copy_setup(ctx, vcpu, &sup_paging, ot_base, minlimit + 1,
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PROT_READ | PROT_WRITE, ot_iov, nitems(ot_iov));
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if (error == 1) {
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/* Restart vcpu execution to handle the page fault */
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return (VMEXIT_RESTART);
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} else if (error == -1) {
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fprintf(stderr, "Error copying in old TSS: %d\n", errno);
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return (VMEXIT_ABORT);
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} else {
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assert(error == 0);
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vm_copyin(ctx, vcpu, ot_iov, &oldtss, minlimit + 1);
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}
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CHKERR(error);
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vm_copyin(ctx, vcpu, ot_iov, &oldtss, minlimit + 1);
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/*
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* Clear the busy bit in the old TSS descriptor if the task switch
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@ -808,8 +830,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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ot_desc.sd_type &= ~0x2;
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error = desc_table_write(ctx, vcpu, &sup_paging, ot_sel,
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&ot_desc);
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if (error)
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return (error);
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CHKERR(error);
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}
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if (nt_type == SDT_SYS286BSY || nt_type == SDT_SYS286TSS) {
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@ -829,8 +850,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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nt_desc.sd_type |= 0x2;
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error = desc_table_write(ctx, vcpu, &sup_paging, nt_sel,
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&nt_desc);
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if (error)
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return (error);
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CHKERR(error);
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}
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/* Update task register to point at the new TSS */
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@ -854,8 +874,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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/* Load processor state from new TSS */
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error = tss32_restore(ctx, vcpu, task_switch, ot_sel, &newtss, nt_iov);
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if (error)
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return (error);
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CHKERR(error);
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/*
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* Section "Interrupt Tasks" in Intel SDM, Vol 3: if an exception
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@ -867,9 +886,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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assert(task_switch->reason == TSR_IDT_GATE);
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error = push_errcode(ctx, vcpu, &task_switch->paging, nt_type,
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task_switch->errcode);
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if (error) {
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return (error);
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}
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CHKERR(error);
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}
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/*
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@ -910,5 +927,6 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
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/*
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* XXX should inject debug exception if 'T' bit is 1
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*/
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return (VMEXIT_RESTART);
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done:
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return (VMEXIT_CONTINUE);
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}
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