KVM: VMX: give unrestricted guest full control of CR3

Sean Christopherson · bonzini · commit b4d185175bc1 · 2018-03-16T22:01:36.000+01:00
Now CR3 is not forced to a host-controlled value when paging is
disabled in an unrestricted guest, CR3 load/store exiting can be
left disabled (for an unrestricted guest).  And because CR0.WP
and CR4.PAE/PSE are also not force to host-controlled values,
all of ept_update_paging_mode_cr0() is no longer needed, i.e.
skip ept_update_paging_mode_cr0() for an unrestricted guest.

Because MOV CR3 no longer exits when paging is disabled for an
unrestricted guest, vmx_decache_cr3() must always read GUEST_CR3
from the VMCS for an unrestricted guest.

Signed-off-by: Sean Christopherson &lt;sean.j.christopherson@intel.com&gt;
Signed-off-by: Radim Krčmář &lt;rkrcmar@redhat.com&gt;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
@@ -4314,7 +4314,7 @@ static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu)
 
 static void vmx_decache_cr3(struct kvm_vcpu *vcpu)
 {
-	if (enable_ept && is_paging(vcpu))
+	if (enable_unrestricted_guest || (enable_ept && is_paging(vcpu)))
 		vcpu->arch.cr3 = vmcs_readl(GUEST_CR3);
 	__set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);
 }
@@ -4451,7 +4451,7 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 	}
 #endif
 
-	if (enable_ept)
+	if (enable_ept && !enable_unrestricted_guest)
 		ept_update_paging_mode_cr0(&hw_cr0, cr0, vcpu);
 
 	vmcs_writel(CR0_READ_SHADOW, cr0);

Original file line number	Diff line number	Diff line change
`@@ -4314,7 +4314,7 @@ static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu)`
`4314`	`4314`
`4315`	`4315`	`static void vmx_decache_cr3(struct kvm_vcpu *vcpu)`
`4316`	`4316`	`{`
`4317`		`- if (enable_ept && is_paging(vcpu))`
	`4317`	`+ if (enable_unrestricted_guest \|\| (enable_ept && is_paging(vcpu)))`
`4318`	`4318`	`vcpu->arch.cr3 = vmcs_readl(GUEST_CR3);`
`4319`	`4319`	`__set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);`
`4320`	`4320`	`}`
`@@ -4451,7 +4451,7 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)`
`4451`	`4451`	`}`
`4452`	`4452`	`#endif`
`4453`	`4453`
`4454`		`- if (enable_ept)`
	`4454`	`+ if (enable_ept && !enable_unrestricted_guest)`
`4455`	`4455`	`ept_update_paging_mode_cr0(&hw_cr0, cr0, vcpu);`
`4456`	`4456`
`4457`	`4457`	`vmcs_writel(CR0_READ_SHADOW, cr0);`