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Subject[PATCH v2 28/46] KVM: VMX: Skip emulation required checks during pmode/rmode transitions
From
Don't refresh "emulation required" when stuffing segments during
transitions to/from real mode when running without unrestricted guest.
The checks are unnecessary as vmx_set_cr0() unconditionally rechecks
"emulation required". They also happen to be broken, as enter_pmode()
and enter_rmode() run with a stale vcpu->arch.cr0.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/vmx.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 45b123bb5aaa..7ab493708b06 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2719,6 +2719,8 @@ static __init int alloc_kvm_area(void)
return 0;
}

+static void __vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);
+
static void fix_pmode_seg(struct kvm_vcpu *vcpu, int seg,
struct kvm_segment *save)
{
@@ -2735,7 +2737,7 @@ static void fix_pmode_seg(struct kvm_vcpu *vcpu, int seg,
save->dpl = save->selector & SEGMENT_RPL_MASK;
save->s = 1;
}
- vmx_set_segment(vcpu, save, seg);
+ __vmx_set_segment(vcpu, save, seg);
}

static void enter_pmode(struct kvm_vcpu *vcpu)
@@ -2756,7 +2758,7 @@ static void enter_pmode(struct kvm_vcpu *vcpu)

vmx->rmode.vm86_active = 0;

- vmx_set_segment(vcpu, &vmx->rmode.segs[VCPU_SREG_TR], VCPU_SREG_TR);
+ __vmx_set_segment(vcpu, &vmx->rmode.segs[VCPU_SREG_TR], VCPU_SREG_TR);

flags = vmcs_readl(GUEST_RFLAGS);
flags &= RMODE_GUEST_OWNED_EFLAGS_BITS;
@@ -3291,7 +3293,7 @@ static u32 vmx_segment_access_rights(struct kvm_segment *var)
return ar;
}

-void vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
+static void __vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
const struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
@@ -3304,7 +3306,7 @@ void vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
vmcs_write16(sf->selector, var->selector);
else if (var->s)
fix_rmode_seg(seg, &vmx->rmode.segs[seg]);
- goto out;
+ return;
}

vmcs_writel(sf->base, var->base);
@@ -3326,9 +3328,13 @@ void vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
var->type |= 0x1; /* Accessed */

vmcs_write32(sf->ar_bytes, vmx_segment_access_rights(var));
+}

-out:
- vmx->emulation_required = emulation_required(vcpu);
+void vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
+{
+ __vmx_set_segment(vcpu, var, seg);
+
+ to_vmx(vcpu)->emulation_required = emulation_required(vcpu);
}

static void vmx_get_cs_db_l_bits(struct kvm_vcpu *vcpu, int *db, int *l)
--
2.32.0.93.g670b81a890-goog
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