MSR_IA32_CR{0,4}_FIXED1 define which bits in CR0 and CR4 are allowed to
be 1 during VMX operation. Since the set of allowed-1 bits is the same
in and out of VMX operation, we can generate these MSRs entirely from
the guest's CPUID. This lets userspace avoiding having to save/restore
these MSRs.
This patch also initializes MSR_IA32_CR{0,4}_FIXED1 from the CPU's MSRs
by default. This is a saner than the current default of -1ull, which
includes bits that the host CPU does not support.
Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
---
arch/x86/kvm/vmx.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 52 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index b414513..49270c4 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2849,16 +2849,18 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
vmx->nested.nested_vmx_basic |= VMX_BASIC_INOUT;
/*
- * These MSRs specify bits which the guest must keep fixed (on or off)
+ * These MSRs specify bits which the guest must keep fixed on
* while L1 is in VMXON mode (in L1's root mode, or running an L2).
* We picked the standard core2 setting.
*/
#define VMXON_CR0_ALWAYSON (X86_CR0_PE | X86_CR0_PG | X86_CR0_NE)
#define VMXON_CR4_ALWAYSON X86_CR4_VMXE
vmx->nested.nested_vmx_cr0_fixed0 = VMXON_CR0_ALWAYSON;
- vmx->nested.nested_vmx_cr0_fixed1 = -1ULL;
vmx->nested.nested_vmx_cr4_fixed0 = VMXON_CR4_ALWAYSON;
- vmx->nested.nested_vmx_cr4_fixed1 = -1ULL;
+
+ /* These MSRs specify bits which the guest must keep fixed off. */
+ rdmsrl(MSR_IA32_VMX_CR0_FIXED1, vmx->nested.nested_vmx_cr0_fixed1);
+ rdmsrl(MSR_IA32_VMX_CR4_FIXED1, vmx->nested.nested_vmx_cr4_fixed1);
/* highest index: VMX_PREEMPTION_TIMER_VALUE */
vmx->nested.nested_vmx_vmcs_enum = 0x2e;
@@ -9547,6 +9549,50 @@ static void vmcs_set_secondary_exec_control(u32 new_ctl)
(new_ctl & ~mask) | (cur_ctl & mask));
}
+/*
+ * Generate MSR_IA32_VMX_CR{0,4}_FIXED1 according to CPUID. Only set bits
+ * (indicating "allowed-1") if they are supported in the guest's CPUID.
+ */
+static void nested_vmx_cr_fixed1_bits_update(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ struct kvm_cpuid_entry2 *entry;
+
+ vmx->nested.nested_vmx_cr0_fixed1 = 0xffffffff;
+ vmx->nested.nested_vmx_cr4_fixed1 = X86_CR4_PCE;
+
+#define cr4_fixed1_update(_cr4_mask, _reg, _cpuid_mask) do { \
+ if (entry && (entry->_reg & (_cpuid_mask))) \
+ vmx->nested.nested_vmx_cr4_fixed1 |= (_cr4_mask); \
+} while (0)
+
+ entry = kvm_find_cpuid_entry(vcpu, 0x1, 0);
+ cr4_fixed1_update(X86_CR4_VME, edx, bit(X86_FEATURE_VME));
+ cr4_fixed1_update(X86_CR4_PVI, edx, bit(X86_FEATURE_VME));
+ cr4_fixed1_update(X86_CR4_TSD, edx, bit(X86_FEATURE_TSC));
+ cr4_fixed1_update(X86_CR4_DE, edx, bit(X86_FEATURE_DE));
+ cr4_fixed1_update(X86_CR4_PSE, edx, bit(X86_FEATURE_PSE));
+ cr4_fixed1_update(X86_CR4_PAE, edx, bit(X86_FEATURE_PAE));
+ cr4_fixed1_update(X86_CR4_MCE, edx, bit(X86_FEATURE_MCE));
+ cr4_fixed1_update(X86_CR4_PGE, edx, bit(X86_FEATURE_PGE));
+ cr4_fixed1_update(X86_CR4_OSFXSR, edx, bit(X86_FEATURE_FXSR));
+ cr4_fixed1_update(X86_CR4_OSXMMEXCPT, edx, bit(X86_FEATURE_XMM));
+ cr4_fixed1_update(X86_CR4_VMXE, ecx, bit(X86_FEATURE_VMX));
+ cr4_fixed1_update(X86_CR4_SMXE, ecx, bit(X86_FEATURE_SMX));
+ cr4_fixed1_update(X86_CR4_PCIDE, ecx, bit(X86_FEATURE_PCID));
+ cr4_fixed1_update(X86_CR4_OSXSAVE, ecx, bit(X86_FEATURE_XSAVE));
+
+ entry = kvm_find_cpuid_entry(vcpu, 0x7, 0);
+ cr4_fixed1_update(X86_CR4_FSGSBASE, ebx, bit(X86_FEATURE_FSGSBASE));
+ cr4_fixed1_update(X86_CR4_SMEP, ebx, bit(X86_FEATURE_SMEP));
+ cr4_fixed1_update(X86_CR4_SMAP, ebx, bit(X86_FEATURE_SMAP));
+ cr4_fixed1_update(X86_CR4_PKE, ecx, bit(X86_FEATURE_PKU));
+ /* TODO: Use X86_CR4_UMIP and X86_FEATURE_UMIP macros */
+ cr4_fixed1_update(bit(11), ecx, bit(2));
+
+#undef cr4_fixed1_update
+}
+
static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
@@ -9588,6 +9634,9 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
else
to_vmx(vcpu)->msr_ia32_feature_control_valid_bits &=
~FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
+
+ if (nested_vmx_allowed(vcpu))
+ nested_vmx_cr_fixed1_bits_update(vcpu);
}
static void vmx_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
--
2.8.0.rc3.226.g39d4020
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