d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Avoid doing unnecessary nested TLB invalidations.

Browse Source 
Prior to this change the cached value of 'pm_eptgen' was tracked per-vcpu
and per-hostcpu. In the degenerate case where 'N' vcpus were sharing
a single hostcpu this could result in 'N - 1' unnecessary TLB invalidations.
Since an 'invept' invalidates mappings for all VPIDs the first 'invept'
is sufficient.

Fix this by moving the 'eptgen[MAXCPU]' array from 'vmxctx' to 'struct vmx'.

If it is known that an 'invept' is going to be done before entering the
guest then it is safe to skip the 'invvpid'. The stat VPU_INVVPID_SAVED
counts the number of 'invvpid' invalidations that were avoided because
they were subsumed by an 'invept'.

Discussed with:	grehan
This commit is contained in:
neel 2014-02-04 02:45:08 +00:00
parent 7cbc3205cc
commit 8f40ca632d
4 changed files with 39 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
sys/amd64/vmm/intel/vmx.c
View File

@ -907,7 +907,6 @@ vmx_vminit(struct vm *vm, pmap_t pmap)
panic("vmx_setup_cr4_shadow %d", error);
vmx->ctx[i].pmap = pmap;
vmx->ctx[i].eptp = vmx->eptp;
}
return (vmx);
@ -955,20 +954,20 @@ vmx_astpending_trace(struct vmx *vmx, int vcpu, uint64_t rip)
#endif
}
static VMM_STAT_INTEL(VCPU_INVVPID_SAVED, "Number of vpid invalidations saved");
static void
vmx_set_pcpu_defaults(struct vmx *vmx, int vcpu)
vmx_set_pcpu_defaults(struct vmx *vmx, int vcpu, pmap_t pmap)
{
int lastcpu;
struct vmxstate *vmxstate;
struct invvpid_desc invvpid_desc = { 0 };
struct invvpid_desc invvpid_desc;
vmxstate = &vmx->state[vcpu];
lastcpu = vmxstate->lastcpu;
vmxstate->lastcpu = curcpu;
if (lastcpu == curcpu)
if (vmxstate->lastcpu == curcpu)
return;
vmxstate->lastcpu = curcpu;
vmm_stat_incr(vmx->vm, vcpu, VCPU_MIGRATIONS, 1);
vmcs_write(VMCS_HOST_TR_BASE, vmm_get_host_trbase());
@ -991,8 +990,20 @@ vmx_set_pcpu_defaults(struct vmx *vmx, int vcpu)
* for "all" EP4TAs.
*/
if (vmxstate->vpid != 0) {
invvpid_desc.vpid = vmxstate->vpid;
invvpid(INVVPID_TYPE_SINGLE_CONTEXT, invvpid_desc);
if (pmap->pm_eptgen == vmx->eptgen[curcpu]) {
invvpid_desc._res1 = 0;
invvpid_desc._res2 = 0;
invvpid_desc.vpid = vmxstate->vpid;
invvpid(INVVPID_TYPE_SINGLE_CONTEXT, invvpid_desc);
} else {
/*
* The invvpid can be skipped if an invept is going to
* be performed before entering the guest. The invept
* will invalidate combined mappings tagged with
* 'vmx->eptp' for all vpids.
*/
vmm_stat_incr(vmx->vm, vcpu, VCPU_INVVPID_SAVED, 1);
}
}
}
@ -1859,8 +1870,6 @@ vmx_run(void *arg, int vcpu, register_t startrip, pmap_t pmap,
KASSERT(vmxctx->pmap == pmap,
("pmap %p different than ctx pmap %p", pmap, vmxctx->pmap));
KASSERT(vmxctx->eptp == vmx->eptp,
("eptp %p different than ctx eptp %#lx", eptp, vmxctx->eptp));
VMPTRLD(vmcs);
@ -1875,7 +1884,7 @@ vmx_run(void *arg, int vcpu, register_t startrip, pmap_t pmap,
vmcs_write(VMCS_HOST_CR3, rcr3());
vmcs_write(VMCS_GUEST_RIP, startrip);
vmx_set_pcpu_defaults(vmx, vcpu);
vmx_set_pcpu_defaults(vmx, vcpu, pmap);
do {
/*
* Interrupts are disabled from this point on until the
@ -1910,7 +1919,7 @@ vmx_run(void *arg, int vcpu, register_t startrip, pmap_t pmap,
vmx_inject_interrupts(vmx, vcpu, vlapic);
vmx_run_trace(vmx, vcpu);
rc = vmx_enter_guest(vmxctx, launched);
rc = vmx_enter_guest(vmxctx, vmx, launched);
enable_intr();

12
sys/amd64/vmm/intel/vmx.h
View File

@ -64,16 +64,13 @@ struct vmxctx {
/*
* XXX todo debug registers and fpu state
*/
int inst_fail_status;
long eptgen[MAXCPU]; /* cached pmap->pm_eptgen */
/*
* The 'eptp' and the 'pmap' do not change during the lifetime of
* the VM so it is safe to keep a copy in each vcpu's vmxctx.
* The pmap needs to be deactivated in vmx_exit_guest()
* so keep a copy of the 'pmap' in each vmxctx.
*/
vm_paddr_t eptp;
struct pmap *pmap;
};
@ -113,6 +110,7 @@ struct vmx {
struct vmxstate state[VM_MAXCPU];
uint64_t eptp;
struct vm *vm;
long eptgen[MAXCPU]; /* cached pmap->pm_eptgen */
};
CTASSERT((offsetof(struct vmx, vmcs) & PAGE_MASK) == 0);
CTASSERT((offsetof(struct vmx, msr_bitmap) & PAGE_MASK) == 0);
@ -123,7 +121,7 @@ CTASSERT((offsetof(struct vmx, pir_desc[0]) & 63) == 0);
#define VMX_VMRESUME_ERROR 1
#define VMX_VMLAUNCH_ERROR 2
#define VMX_INVEPT_ERROR 3
int vmx_enter_guest(struct vmxctx *ctx, int launched);
int vmx_enter_guest(struct vmxctx *ctx, struct vmx *vmx, int launched);
void vmx_exit_guest(void);
void vmx_call_isr(uintptr_t entry);

6
sys/amd64/vmm/intel/vmx_genassym.c
View File

@ -68,10 +68,10 @@ ASSYM(VMXCTX_HOST_RBX, offsetof(struct vmxctx, host_rbx));
ASSYM(VMXCTX_HOST_RIP, offsetof(struct vmxctx, host_rip));
ASSYM(VMXCTX_INST_FAIL_STATUS, offsetof(struct vmxctx, inst_fail_status));
ASSYM(VMXCTX_EPTGEN, offsetof(struct vmxctx, eptgen));
ASSYM(VMXCTX_PMAP, offsetof(struct vmxctx, pmap));
ASSYM(VMXCTX_EPTP, offsetof(struct vmxctx, eptp));
ASSYM(VMX_EPTGEN, offsetof(struct vmx, eptgen));
ASSYM(VMX_EPTP, offsetof(struct vmx, eptp));
ASSYM(VM_FAIL_INVALID, VM_FAIL_INVALID);
ASSYM(VM_FAIL_VALID, VM_FAIL_VALID);

15
sys/amd64/vmm/intel/vmx_support.S
View File

@ -97,7 +97,8 @@
/*
* vmx_enter_guest(struct vmxctx *vmxctx, int launched)
* %rdi: pointer to the 'vmxctx'
* %esi: launch state of the VMCS
* %rsi: pointer to the 'vmx'
* %edx: launch state of the VMCS
* Interrupts must be disabled on entry.
*/
ENTRY(vmx_enter_guest)
@ -114,19 +115,19 @@ ENTRY(vmx_enter_guest)
LK btsl %eax, PM_ACTIVE(%r11)
/*
* If 'vmxctx->eptgen[curcpu]' is not identical to 'pmap->pm_eptgen'
* If 'vmx->eptgen[curcpu]' is not identical to 'pmap->pm_eptgen'
* then we must invalidate all mappings associated with this EPTP.
*/
movq PM_EPTGEN(%r11), %r10
cmpq %r10, VMXCTX_EPTGEN(%rdi, %rax, 8)
cmpq %r10, VMX_EPTGEN(%rsi, %rax, 8)
je guest_restore
/* Refresh 'vmxctx->eptgen[curcpu]' */
movq %r10, VMXCTX_EPTGEN(%rdi, %rax, 8)
/* Refresh 'vmx->eptgen[curcpu]' */
movq %r10, VMX_EPTGEN(%rsi, %rax, 8)
/* Setup the invept descriptor on the host stack */
mov %rsp, %r11
movq VMXCTX_EPTP(%rdi), %rax
movq VMX_EPTP(%rsi), %rax
movq %rax, -16(%r11)
movq $0x0, -8(%r11)
mov $0x1, %eax /* Single context invalidate */
@ -134,7 +135,7 @@ ENTRY(vmx_enter_guest)
jbe invept_error /* Check invept instruction error */
guest_restore:
cmpl $0, %esi
cmpl $0, %edx
je do_launch
VMX_GUEST_RESTORE