This patch allows the guest to enable the VMXE bit in CR4, which is a
prerequisite to running VMXON.
Whether to allow setting the VMXE bit now depends on the architecture (svm
or vmx), so its checking has moved to kvm_x86_ops->set_cr4(). This function
now returns an int: If kvm_x86_ops->set_cr4() returns 1, __kvm_set_cr4()
will also return 1, and this will cause kvm_set_cr4() will throw a #GP.
Turning on the VMXE bit is allowed only when the "nested" module option is on,
and turning it off is forbidden after a vmxon.
Signed-off-by: Nadav Har'El <nyh@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/svm.c | 6 +++++-
arch/x86/kvm/vmx.c | 13 +++++++++++--
arch/x86/kvm/x86.c | 4 +---
4 files changed, 18 insertions(+), 7 deletions(-)
--- .before/arch/x86/include/asm/kvm_host.h 2010-10-17 11:52:00.000000000 +0200
+++ .after/arch/x86/include/asm/kvm_host.h 2010-10-17 11:52:00.000000000 +0200
@@ -532,7 +532,7 @@ struct kvm_x86_ops {
void (*decache_cr4_guest_bits)(struct kvm_vcpu *vcpu);
void (*set_cr0)(struct kvm_vcpu *vcpu, unsigned long cr0);
void (*set_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);
- void (*set_cr4)(struct kvm_vcpu *vcpu, unsigned long cr4);
+ int (*set_cr4)(struct kvm_vcpu *vcpu, unsigned long cr4);
void (*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);
--- .before/arch/x86/kvm/svm.c 2010-10-17 11:52:00.000000000 +0200
+++ .after/arch/x86/kvm/svm.c 2010-10-17 11:52:00.000000000 +0200
@@ -1271,11 +1271,14 @@ static void svm_set_cr0(struct kvm_vcpu
update_cr0_intercept(svm);
}
-static void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
+static int svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
unsigned long host_cr4_mce = read_cr4() & X86_CR4_MCE;
unsigned long old_cr4 = to_svm(vcpu)->vmcb->save.cr4;
+ if (cr4 & X86_CR4_VMXE)
+ return 1;
+
if (npt_enabled && ((old_cr4 ^ cr4) & X86_CR4_PGE))
force_new_asid(vcpu);
@@ -1284,6 +1287,7 @@ static void svm_set_cr4(struct kvm_vcpu
cr4 |= X86_CR4_PAE;
cr4 |= host_cr4_mce;
to_svm(vcpu)->vmcb->save.cr4 = cr4;
+ return 0;
}
static void svm_set_segment(struct kvm_vcpu *vcpu,
--- .before/arch/x86/kvm/x86.c 2010-10-17 11:52:00.000000000 +0200
+++ .after/arch/x86/kvm/x86.c 2010-10-17 11:52:00.000000000 +0200
@@ -603,11 +603,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, u
&& !load_pdptrs(vcpu, vcpu->arch.walk_mmu, vcpu->arch.cr3))
return 1;
- if (cr4 & X86_CR4_VMXE)
+ if (kvm_x86_ops->set_cr4(vcpu, cr4))
return 1;
- kvm_x86_ops->set_cr4(vcpu, cr4);
-
if ((cr4 ^ old_cr4) & pdptr_bits)
kvm_mmu_reset_context(vcpu);
--- .before/arch/x86/kvm/vmx.c 2010-10-17 11:52:00.000000000 +0200
+++ .after/arch/x86/kvm/vmx.c 2010-10-17 11:52:00.000000000 +0200
@@ -1880,7 +1880,7 @@ static void ept_save_pdptrs(struct kvm_v
(unsigned long *)&vcpu->arch.regs_dirty);
}
-static void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
+static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
unsigned long cr0,
@@ -1975,11 +1975,19 @@ static void vmx_set_cr3(struct kvm_vcpu
vmcs_writel(GUEST_CR3, guest_cr3);
}
-static void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
+static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
unsigned long hw_cr4 = cr4 | (to_vmx(vcpu)->rmode.vm86_active ?
KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
+ if (cr4 & X86_CR4_VMXE){
+ if (!nested)
+ return 1;
+ } else {
+ if (nested && to_vmx(vcpu)->nested.vmxon)
+ return 1;
+ }
+
vcpu->arch.cr4 = cr4;
if (enable_ept) {
if (!is_paging(vcpu)) {
@@ -1992,6 +2000,7 @@ static void vmx_set_cr4(struct kvm_vcpu
vmcs_writel(CR4_READ_SHADOW, cr4);
vmcs_writel(GUEST_CR4, hw_cr4);
+ return 0;
}
static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg)
--
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