[PATCH 5.10 502/545] KVM: x86: Move vendor CR4 validity check to dedicated kvm_x86_ops hook

Greg Kroah-Hartman
2022-08-19T16:48:42Z

From: Sean Christopherson <sean.j.christopherson@intel.com>

[ Upstream commit c2fe3cd4604ac87c587db05d41843d667dc43815 ]

Split out VMX's checks on CR4.VMXE to a dedicated hook, .is_valid_cr4(),
and invoke the new hook from kvm_valid_cr4(). This fixes an issue where
KVM_SET_SREGS would return success while failing to actually set CR4.

Fixing the issue by explicitly checking kvm_x86_ops.set_cr4()'s return
in __set_sregs() is not a viable option as KVM has already stuffed a
variety of vCPU state.

Note, kvm_valid_cr4() and is_valid_cr4() have different return types and
inverted semantics. This will be remedied in a future patch.

Fixes: 5e1746d6205d ("KVM: nVMX: Allow setting the VMXE bit in CR4")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20201007014417.29276-5-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/include/asm/kvm_host.h | 3 ++-
arch/x86/kvm/svm/svm.c | 9 +++++++--
arch/x86/kvm/svm/svm.h | 2 +-
arch/x86/kvm/vmx/nested.c | 2 +-
arch/x86/kvm/vmx/vmx.c | 31 ++++++++++++++++++-------------
arch/x86/kvm/vmx/vmx.h | 2 +-
arch/x86/kvm/x86.c | 6 ++++--
7 files changed, 34 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 94fbbdb888cf..87c13ef4ee8e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1117,7 +1117,8 @@ struct kvm_x86_ops {
struct kvm_segment *var, int seg);
void (*get_cs_db_l_bits)(struct kvm_vcpu *vcpu, int *db, int *l);
void (*set_cr0)(struct kvm_vcpu *vcpu, unsigned long cr0);
- int (*set_cr4)(struct kvm_vcpu *vcpu, unsigned long cr4);
+ bool (*is_valid_cr4)(struct kvm_vcpu *vcpu, unsigned long cr0);
+ void (*set_cr4)(struct kvm_vcpu *vcpu, unsigned long cr4);
int (*set_efer)(struct kvm_vcpu *vcpu, u64 efer);
void (*get_idt)(struct kvm_vcpu *vcpu, struct desc_ptr *dt);
void (*set_idt)(struct kvm_vcpu *vcpu, struct desc_ptr *dt);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 9bc166a5d453..442705517caf 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1692,7 +1692,12 @@ void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
update_cr0_intercept(svm);
}

-int svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
+static bool svm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
+{
+ return true;
+}
+
+void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
unsigned long host_cr4_mce = cr4_read_shadow() & X86_CR4_MCE;
unsigned long old_cr4 = to_svm(vcpu)->vmcb->save.cr4;
@@ -1706,7 +1711,6 @@ int svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
cr4 |= host_cr4_mce;
to_svm(vcpu)->vmcb->save.cr4 = cr4;
vmcb_mark_dirty(to_svm(vcpu)->vmcb, VMCB_CR);
- return 0;
}

static void svm_set_segment(struct kvm_vcpu *vcpu,
@@ -4238,6 +4242,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
.get_cpl = svm_get_cpl,
.get_cs_db_l_bits = kvm_get_cs_db_l_bits,
.set_cr0 = svm_set_cr0,
+ .is_valid_cr4 = svm_is_valid_cr4,
.set_cr4 = svm_set_cr4,
.set_efer = svm_set_efer,
.get_idt = svm_get_idt,
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 2c007241fbf5..10aba1dd264e 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -355,7 +355,7 @@ void svm_vcpu_free_msrpm(u32 *msrpm);

int svm_set_efer(struct kvm_vcpu *vcpu, u64 efer);
void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
-int svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
+void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
void svm_flush_tlb(struct kvm_vcpu *vcpu);
void disable_nmi_singlestep(struct vcpu_svm *svm);
bool svm_smi_blocked(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index c4e37d81b158..3228db4db5df 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4879,7 +4879,7 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
/*
* The Intel VMX Instruction Reference lists a bunch of bits that are
* prerequisite to running VMXON, most notably cr4.VMXE must be set to
- * 1 (see vmx_set_cr4() for when we allow the guest to set this).
+ * 1 (see vmx_is_valid_cr4() for when we allow the guest to set this).
* Otherwise, we should fail with #UD. But most faulting conditions
* have already been checked by hardware, prior to the VM-exit for
* VMXON. We do test guest cr4.VMXE because processor CR4 always has
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 154ec5d8cdf5..b33d0f283d4f 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3183,7 +3183,23 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long pgd,
vmcs_writel(GUEST_CR3, guest_cr3);
}

-int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
+static bool vmx_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
+{
+ /*
+ * We operate under the default treatment of SMM, so VMX cannot be
+ * enabled under SMM. Note, whether or not VMXE is allowed at all is
+ * handled by kvm_valid_cr4().
+ */
+ if ((cr4 & X86_CR4_VMXE) && is_smm(vcpu))
+ return false;
+
+ if (to_vmx(vcpu)->nested.vmxon && !nested_cr4_valid(vcpu, cr4))
+ return false;
+
+ return true;
+}
+
+void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
/*
@@ -3211,17 +3227,6 @@ int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
}
}

- /*
- * We operate under the default treatment of SMM, so VMX cannot be
- * enabled under SMM. Note, whether or not VMXE is allowed at all is
- * handled by kvm_valid_cr4().
- */
- if ((cr4 & X86_CR4_VMXE) && is_smm(vcpu))
- return 1;
-
- if (vmx->nested.vmxon && !nested_cr4_valid(vcpu, cr4))
- return 1;
-
vcpu->arch.cr4 = cr4;
kvm_register_mark_available(vcpu, VCPU_EXREG_CR4);

@@ -3252,7 +3257,6 @@ int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)

vmcs_writel(CR4_READ_SHADOW, cr4);
vmcs_writel(GUEST_CR4, hw_cr4);
- return 0;
}

void vmx_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
@@ -7748,6 +7752,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
.get_cpl = vmx_get_cpl,
.get_cs_db_l_bits = vmx_get_cs_db_l_bits,
.set_cr0 = vmx_set_cr0,
+ .is_valid_cr4 = vmx_is_valid_cr4,
.set_cr4 = vmx_set_cr4,
.set_efer = vmx_set_efer,
.get_idt = vmx_get_idt,
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index a6b52d3a39c9..24903f05c204 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -347,7 +347,7 @@ u32 vmx_get_interrupt_shadow(struct kvm_vcpu *vcpu);
void vmx_set_interrupt_shadow(struct kvm_vcpu *vcpu, int mask);
int vmx_set_efer(struct kvm_vcpu *vcpu, u64 efer);
void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
-int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
+void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
void set_cr4_guest_host_mask(struct vcpu_vmx *vmx);
void ept_save_pdptrs(struct kvm_vcpu *vcpu);
void vmx_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 98422a53bb1e..5f4f855bb3b1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -986,6 +986,9 @@ int kvm_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
if (cr4 & vcpu->arch.cr4_guest_rsvd_bits)
return -EINVAL;

+ if (!kvm_x86_ops.is_valid_cr4(vcpu, cr4))
+ return -EINVAL;
+
return 0;
}
EXPORT_SYMBOL_GPL(kvm_valid_cr4);
@@ -1020,8 +1023,7 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
return 1;
}

- if (kvm_x86_ops.set_cr4(vcpu, cr4))
- return 1;
+ kvm_x86_ops.set_cr4(vcpu, cr4);

if (((cr4 ^ old_cr4) & mmu_role_bits) ||
(!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE)))
--
2.35.1