Commit 1dd7a4f1 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: VMX: Skip emulation required checks during pmode/rmode transitions 



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: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-29-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 32437c2a

arch/x86/kvm/vmx/vmx.c

+12 −6
Original line number Diff line number Diff line
@@ -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)