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Consolidate the code to restore the host TSS after a #VMEXIT into a single

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function restore_host_tss().

Don't bother to restore MSR_KGSBASE after a #VMEXIT since it is not used in
the kernel. It will be restored on return to userspace.

Discussed with:	Anish Gupta (akgupt3@gmail.com)
This commit is contained in:
Neel Natu 2014-09-04 06:00:18 +00:00
parent 246e7a2b64
commit fea6bd5cd3
1 changed files with 24 additions and 30 deletions
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54
sys/amd64/vmm/amd/svm.c
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@ -1104,22 +1104,21 @@ svm_inj_interrupts(struct svm_softc *svm_sc, int vcpu, struct vlapic *vlapic)
VCPU_CTR1(svm_sc->vm, vcpu, "SVM:event injected,vector=%d.\n", vector);
}
/*
* Restore host Task Register selector type after every vcpu exit.
*/
static void
setup_tss_type(void)
restore_host_tss(void)
{
struct system_segment_descriptor *desc;
struct system_segment_descriptor *tss_sd;
desc = (struct system_segment_descriptor *)&gdt[curcpu * NGDT +
GPROC0_SEL];
/*
* Task selector that should be restored in host is
* 64-bit available(9), not what is read(0xb), see
* APMvol2 Rev3.21 4.8.3 System Descriptors table.
* The TSS descriptor was in use prior to launching the guest so it
* has been marked busy.
*
* 'ltr' requires the descriptor to be marked available so change the
* type to "64-bit available TSS".
*/
desc->sd_type = 9;
tss_sd = PCPU_GET(tss);
tss_sd->sd_type = SDT_SYSTSS;
ltr(GSEL(GPROC0_SEL, SEL_KPL));
}
/*
@ -1241,32 +1240,27 @@ svm_vmrun(void *arg, int vcpu, register_t rip, pmap_t pmap,
svm_inj_interrupts(svm_sc, vcpu, vlapic);
/* Change TSS type to available.*/
setup_tss_type();
/* Launch Virtual Machine. */
svm_launch(vmcb_pa, gctx, hctx);
/*
* Only GDTR and IDTR of host is saved and restore by SVM,
* LDTR and TR need to be restored by VMM.
* XXX: kernel doesn't use LDT, only user space.
*/
ltr(GSEL(GPROC0_SEL, SEL_KPL));
/*
* Guest FS and GS selector are stashed by vmload and vmsave.
* Host FS and GS selector are stashed by svm_launch().
* Host GS base that holds per-cpu need to be restored before
* enabling global interrupt.
* FS is not used by FreeBSD kernel and kernel does restore
* back FS selector and base of user before returning to
* userland.
* Restore MSR_GSBASE to point to the pcpu data area.
*
* Note: You can't use 'curcpu' which uses pcpu.
* Note that accesses done via PCPU_GET/PCPU_SET will work
* only after MSR_GSBASE is restored.
*
* Also note that we don't bother restoring MSR_KGSBASE
* since it is not used in the kernel and will be restored
* when the VMRUN ioctl returns to userspace.
*/
wrmsr(MSR_GSBASE, (uint64_t)&__pcpu[vcpustate->lastcpu]);
wrmsr(MSR_KGSBASE, (uint64_t)&__pcpu[vcpustate->lastcpu]);
/*
* The host GDTR and IDTR is saved by VMRUN and restored
* automatically on #VMEXIT. However, the host TSS needs
* to be restored explicitly.
*/
restore_host_tss();
/* #VMEXIT disables interrupts so re-enable them here. */
enable_gintr();