[PATCH 5.15 086/128] KVM: x86: Always set kvm_run->if_flag

Greg Kroah-Hartman
2021-12-27T15:53:40Z

From: Marc Orr <marcorr@google.com>

commit c5063551bfcae4e48fec890b7bf369598b77526b upstream.

The kvm_run struct's if_flag is a part of the userspace/kernel API. The
SEV-ES patches failed to set this flag because it's no longer needed by
QEMU (according to the comment in the source code). However, other
hypervisors may make use of this flag. Therefore, set the flag for
guests with encrypted registers (i.e., with guest_state_protected set).

Fixes: f1c6366e3043 ("KVM: SVM: Add required changes to support intercepts under SEV-ES")
Signed-off-by: Marc Orr <marcorr@google.com>
Message-Id: <20211209155257.128747-1-marcorr@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/include/asm/kvm-x86-ops.h | 1 +
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/svm/svm.c | 21 ++++++++++++---------
arch/x86/kvm/vmx/vmx.c | 6 ++++++
arch/x86/kvm/x86.c | 9 +--------
5 files changed, 21 insertions(+), 17 deletions(-)

--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -47,6 +47,7 @@ KVM_X86_OP(set_dr7)
KVM_X86_OP(cache_reg)
KVM_X86_OP(get_rflags)
KVM_X86_OP(set_rflags)
+KVM_X86_OP(get_if_flag)
KVM_X86_OP(tlb_flush_all)
KVM_X86_OP(tlb_flush_current)
KVM_X86_OP_NULL(tlb_remote_flush)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1341,6 +1341,7 @@ struct kvm_x86_ops {
void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
+ bool (*get_if_flag)(struct kvm_vcpu *vcpu);

void (*tlb_flush_all)(struct kvm_vcpu *vcpu);
void (*tlb_flush_current)(struct kvm_vcpu *vcpu);
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1517,6 +1517,15 @@ static void svm_set_rflags(struct kvm_vc
to_svm(vcpu)->vmcb->save.rflags = rflags;
}

+static bool svm_get_if_flag(struct kvm_vcpu *vcpu)
+{
+ struct vmcb *vmcb = to_svm(vcpu)->vmcb;
+
+ return sev_es_guest(vcpu->kvm)
+ ? vmcb->control.int_state & SVM_GUEST_INTERRUPT_MASK
+ : kvm_get_rflags(vcpu) & X86_EFLAGS_IF;
+}
+
static void svm_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
{
switch (reg) {
@@ -3485,14 +3494,7 @@ bool svm_interrupt_blocked(struct kvm_vc
if (!gif_set(svm))
return true;

- if (sev_es_guest(vcpu->kvm)) {
- /*
- * SEV-ES guests to not expose RFLAGS. Use the VMCB interrupt mask
- * bit to determine the state of the IF flag.
- */
- if (!(vmcb->control.int_state & SVM_GUEST_INTERRUPT_MASK))
- return true;
- } else if (is_guest_mode(vcpu)) {
+ if (is_guest_mode(vcpu)) {
/* As long as interrupts are being delivered... */
if ((svm->nested.ctl.int_ctl & V_INTR_MASKING_MASK)
? !(svm->vmcb01.ptr->save.rflags & X86_EFLAGS_IF)
@@ -3503,7 +3505,7 @@ bool svm_interrupt_blocked(struct kvm_vc
if (nested_exit_on_intr(svm))
return false;
} else {
- if (!(kvm_get_rflags(vcpu) & X86_EFLAGS_IF))
+ if (!svm_get_if_flag(vcpu))
return true;
}

@@ -4562,6 +4564,7 @@ static struct kvm_x86_ops svm_x86_ops __
.cache_reg = svm_cache_reg,
.get_rflags = svm_get_rflags,
.set_rflags = svm_set_rflags,
+ .get_if_flag = svm_get_if_flag,

.tlb_flush_all = svm_flush_tlb,
.tlb_flush_current = svm_flush_tlb,
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1359,6 +1359,11 @@ void vmx_set_rflags(struct kvm_vcpu *vcp
vmx->emulation_required = vmx_emulation_required(vcpu);
}

+static bool vmx_get_if_flag(struct kvm_vcpu *vcpu)
+{
+ return vmx_get_rflags(vcpu) & X86_EFLAGS_IF;
+}
+
u32 vmx_get_interrupt_shadow(struct kvm_vcpu *vcpu)
{
u32 interruptibility = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO);
@@ -7573,6 +7578,7 @@ static struct kvm_x86_ops vmx_x86_ops __
.cache_reg = vmx_cache_reg,
.get_rflags = vmx_get_rflags,
.set_rflags = vmx_set_rflags,
+ .get_if_flag = vmx_get_if_flag,

.tlb_flush_all = vmx_flush_tlb_all,
.tlb_flush_current = vmx_flush_tlb_current,
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8880,14 +8880,7 @@ static void post_kvm_run_save(struct kvm
{
struct kvm_run *kvm_run = vcpu->run;

- /*
- * if_flag is obsolete and useless, so do not bother
- * setting it for SEV-ES guests. Userspace can just
- * use kvm_run->ready_for_interrupt_injection.
- */
- kvm_run->if_flag = !vcpu->arch.guest_state_protected
- && (kvm_get_rflags(vcpu) & X86_EFLAGS_IF) != 0;
-
+ kvm_run->if_flag = static_call(kvm_x86_get_if_flag)(vcpu);
kvm_run->cr8 = kvm_get_cr8(vcpu);
kvm_run->apic_base = kvm_get_apic_base(vcpu);