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KVM: SVM: Provide an updated VMRUN invocation for SEV-ES guests

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The run sequence is different for an SEV-ES guest compared to a legacy or
even an SEV guest. The guest vCPU register state of an SEV-ES guest will
be restored on VMRUN and saved on VMEXIT. There is no need to restore the
guest registers directly and through VMLOAD before VMRUN and no need to
save the guest registers directly and through VMSAVE on VMEXIT.

Update the svm_vcpu_run() function to skip register state saving and
restoring and provide an alternative function for running an SEV-ES guest
in vmenter.S

Additionally, certain host state is restored across an SEV-ES VMRUN. As
a result certain register states are not required to be restored upon
VMEXIT (e.g. FS, GS, etc.), so only do that if the guest is not an SEV-ES
guest.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <fb1c66d32f2194e171b95fc1a8affd6d326e10c1.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Tom Lendacky 2020-12-10 11:10:08 -06:00 committed by Paolo Bonzini
parent 861377730a
commit 16809ecdc1
4 changed files with 77 additions and 9 deletions
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7
arch/x86/kvm/svm/svm.c
View File

@ -3700,6 +3700,9 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu,
guest_enter_irqoff();
lockdep_hardirqs_on(CALLER_ADDR0);
if (sev_es_guest(svm->vcpu.kvm)) {
__svm_sev_es_vcpu_run(svm->vmcb_pa);
} else {
__svm_vcpu_run(svm->vmcb_pa, (unsigned long *)&svm->vcpu.arch.regs);
#ifdef CONFIG_X86_64
@ -3710,6 +3713,7 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu,
loadsegment(gs, svm->host.gs);
#endif
#endif
}
/*
* VMEXIT disables interrupts (host state), but tracing and lockdep
@ -3807,14 +3811,17 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
if (unlikely(!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL)))
svm->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL);
if (!sev_es_guest(svm->vcpu.kvm))
reload_tss(vcpu);
x86_spec_ctrl_restore_host(svm->spec_ctrl, svm->virt_spec_ctrl);
if (!sev_es_guest(svm->vcpu.kvm)) {
vcpu->arch.cr2 = svm->vmcb->save.cr2;
vcpu->arch.regs[VCPU_REGS_RAX] = svm->vmcb->save.rax;
vcpu->arch.regs[VCPU_REGS_RSP] = svm->vmcb->save.rsp;
vcpu->arch.regs[VCPU_REGS_RIP] = svm->vmcb->save.rip;
}
if (unlikely(svm->vmcb->control.exit_code == SVM_EXIT_NMI))
kvm_before_interrupt(&svm->vcpu);

5
arch/x86/kvm/svm/svm.h
View File

@ -591,4 +591,9 @@ void sev_es_create_vcpu(struct vcpu_svm *svm);
void sev_es_vcpu_load(struct vcpu_svm *svm, int cpu);
void sev_es_vcpu_put(struct vcpu_svm *svm);
/* vmenter.S */
void __svm_sev_es_vcpu_run(unsigned long vmcb_pa);
void __svm_vcpu_run(unsigned long vmcb_pa, unsigned long *regs);
#endif

50
arch/x86/kvm/svm/vmenter.S
View File

@ -168,3 +168,53 @@ SYM_FUNC_START(__svm_vcpu_run)
pop %_ASM_BP
ret
SYM_FUNC_END(__svm_vcpu_run)
/**
* __svm_sev_es_vcpu_run - Run a SEV-ES vCPU via a transition to SVM guest mode
* @vmcb_pa: unsigned long
*/
SYM_FUNC_START(__svm_sev_es_vcpu_run)
push %_ASM_BP
#ifdef CONFIG_X86_64
push %r15
push %r14
push %r13
push %r12
#else
push %edi
push %esi
#endif
push %_ASM_BX
/* Enter guest mode */
mov %_ASM_ARG1, %_ASM_AX
sti
1: vmrun %_ASM_AX
jmp 3f
2: cmpb $0, kvm_rebooting
jne 3f
ud2
_ASM_EXTABLE(1b, 2b)
3: cli
#ifdef CONFIG_RETPOLINE
/* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
FILL_RETURN_BUFFER %_ASM_AX, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
#endif
pop %_ASM_BX
#ifdef CONFIG_X86_64
pop %r12
pop %r13
pop %r14
pop %r15
#else
pop %esi
pop %edi
#endif
pop %_ASM_BP
ret
SYM_FUNC_END(__svm_sev_es_vcpu_run)

6
arch/x86/kvm/x86.c
View File

@ -880,6 +880,9 @@ EXPORT_SYMBOL_GPL(kvm_lmsw);
void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu)
{
if (vcpu->arch.guest_state_protected)
return;
if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE)) {
if (vcpu->arch.xcr0 != host_xcr0)
@ -900,6 +903,9 @@ EXPORT_SYMBOL_GPL(kvm_load_guest_xsave_state);
void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu)
{
if (vcpu->arch.guest_state_protected)
return;
if (static_cpu_has(X86_FEATURE_PKU) &&
(kvm_read_cr4_bits(vcpu, X86_CR4_PKE) ||
(vcpu->arch.xcr0 & XFEATURE_MASK_PKRU))) {