[PATCH v2 21/46] KVM: VMX: Invert handling of CR0.WP for EPT without unrestricted guest

From: Sean Christopherson
Date: Tue Jul 13 2021 - 12:34:43 EST


Opt-in to forcing CR0.WP=1 for shadow paging, and stop lying about WP
being "always on" for unrestricted guest. In addition to making KVM a
wee bit more honest, this paves the way for additional cleanup.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f506b94539ab..02aec75ec6f6 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -136,8 +136,7 @@ module_param(allow_smaller_maxphyaddr, bool, S_IRUGO);
#define KVM_VM_CR0_ALWAYS_OFF (X86_CR0_NW | X86_CR0_CD)
#define KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST X86_CR0_NE
#define KVM_VM_CR0_ALWAYS_ON \
- (KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST | \
- X86_CR0_WP | X86_CR0_PG | X86_CR0_PE)
+ (KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST | X86_CR0_PG | X86_CR0_PE)

#define KVM_VM_CR4_ALWAYS_ON_UNRESTRICTED_GUEST X86_CR4_VMXE
#define KVM_PMODE_VM_CR4_ALWAYS_ON (X86_CR4_PAE | X86_CR4_VMXE)
@@ -2995,9 +2994,7 @@ void ept_save_pdptrs(struct kvm_vcpu *vcpu)
kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);
}

-static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
- unsigned long cr0,
- struct kvm_vcpu *vcpu)
+static void ept_update_paging_mode_cr0(unsigned long cr0, struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);

@@ -3016,9 +3013,6 @@ static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
vcpu->arch.cr0 = cr0;
vmx_set_cr4(vcpu, kvm_read_cr4(vcpu));
}
-
- if (!(cr0 & X86_CR0_WP))
- *hw_cr0 &= ~X86_CR0_WP;
}

void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
@@ -3031,6 +3025,8 @@ void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
hw_cr0 |= KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST;
else {
hw_cr0 |= KVM_VM_CR0_ALWAYS_ON;
+ if (!enable_ept)
+ hw_cr0 |= X86_CR0_WP;

if (vmx->rmode.vm86_active && (cr0 & X86_CR0_PE))
enter_pmode(vcpu);
@@ -3049,7 +3045,7 @@ void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
#endif

if (enable_ept && !is_unrestricted_guest(vcpu))
- ept_update_paging_mode_cr0(&hw_cr0, cr0, vcpu);
+ ept_update_paging_mode_cr0(cr0, vcpu);

vmcs_writel(CR0_READ_SHADOW, cr0);
vmcs_writel(GUEST_CR0, hw_cr0);
--
2.32.0.93.g670b81a890-goog