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KVM: SVM: include CR3 in initial VMSA state for SEV-ES guests

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Normally guests will set up CR3 themselves, but some guests, such as
kselftests, and potentially CONFIG_PVH guests, rely on being booted
with paging enabled and CR3 initialized to a pre-allocated page table.

Currently CR3 updates via KVM_SET_SREGS* are not loaded into the guest
VMCB until just prior to entering the guest. For SEV-ES/SEV-SNP, this
is too late, since it will have switched over to using the VMSA page
prior to that point, with the VMSA CR3 copied from the VMCB initial
CR3 value: 0.

Address this by sync'ing the CR3 value into the VMCB save area
immediately when KVM_SET_SREGS* is issued so it will find it's way into
the initial VMSA.

Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-Id: <20211216171358.61140-10-michael.roth@amd.com>
[Remove vmx_post_set_cr3; add a remark about kvm_set_cr3 not calling the
 new hook. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Michael Roth 2021-12-16 11:13:54 -06:00 committed by Paolo Bonzini
parent 907d139318
commit 405329fc9a
5 changed files with 24 additions and 0 deletions
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1
arch/x86/include/asm/kvm-x86-ops.h
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@ -35,6 +35,7 @@ KVM_X86_OP(get_cpl)
KVM_X86_OP(set_segment)
KVM_X86_OP_NULL(get_cs_db_l_bits)
KVM_X86_OP(set_cr0)
KVM_X86_OP_NULL(post_set_cr3)
KVM_X86_OP(is_valid_cr4)
KVM_X86_OP(set_cr4)
KVM_X86_OP(set_efer)

1
arch/x86/include/asm/kvm_host.h
View File

@ -1344,6 +1344,7 @@ struct kvm_x86_ops {
struct kvm_segment *var, int seg);
void (*get_cs_db_l_bits)(struct kvm_vcpu *vcpu, int *db, int *l);
void (*set_cr0)(struct kvm_vcpu *vcpu, unsigned long cr0);
void (*post_set_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);
bool (*is_valid_cr4)(struct kvm_vcpu *vcpu, unsigned long cr0);
void (*set_cr4)(struct kvm_vcpu *vcpu, unsigned long cr4);
int (*set_efer)(struct kvm_vcpu *vcpu, u64 efer);

19
arch/x86/kvm/svm/svm.c
View File

@ -1801,6 +1801,24 @@ static void svm_set_gdt(struct kvm_vcpu *vcpu, struct desc_ptr *dt)
vmcb_mark_dirty(svm->vmcb, VMCB_DT);
}
static void svm_post_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
{
struct vcpu_svm *svm = to_svm(vcpu);
/*
* For guests that don't set guest_state_protected, the cr3 update is
* handled via kvm_mmu_load() while entering the guest. For guests
* that do (SEV-ES/SEV-SNP), the cr3 update needs to be written to
* VMCB save area now, since the save area will become the initial
* contents of the VMSA, and future VMCB save area updates won't be
* seen.
*/
if (sev_es_guest(vcpu->kvm)) {
svm->vmcb->save.cr3 = cr3;
vmcb_mark_dirty(svm->vmcb, VMCB_CR);
}
}
void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
{
struct vcpu_svm *svm = to_svm(vcpu);
@ -4624,6 +4642,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
.get_cpl = svm_get_cpl,
.get_cs_db_l_bits = kvm_get_cs_db_l_bits,
.set_cr0 = svm_set_cr0,
.post_set_cr3 = svm_post_set_cr3,
.is_valid_cr4 = svm_is_valid_cr4,
.set_cr4 = svm_set_cr4,
.set_efer = svm_set_efer,

1
arch/x86/kvm/vmx/vmx.c
View File

@ -3134,6 +3134,7 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa,
vmcs_writel(GUEST_CR3, guest_cr3);
}
static bool vmx_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
/*

2
arch/x86/kvm/x86.c
View File

@ -1179,6 +1179,7 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
vcpu->arch.cr3 = cr3;
kvm_register_mark_dirty(vcpu, VCPU_EXREG_CR3);
/* Do not call post_set_cr3, we do not get here for confidential guests. */
handle_tlb_flush:
/*
@ -10618,6 +10619,7 @@ static int __set_sregs_common(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs,
*mmu_reset_needed |= kvm_read_cr3(vcpu) != sregs->cr3;
vcpu->arch.cr3 = sregs->cr3;
kvm_register_mark_dirty(vcpu, VCPU_EXREG_CR3);
static_call_cond(kvm_x86_post_set_cr3)(vcpu, sregs->cr3);
kvm_set_cr8(vcpu, sregs->cr8);