[PATCH 4/4] KVM: x86: Add macro to ensure reserved cr4 bits checks stay in sync

From: Sean Christopherson
Date: Tue Dec 10 2019 - 17:44:35 EST


Add a helper macro to generate the set of reserved cr4 bits for both
host and guest to ensure that adding a check on guest capabilities is
also added for host capabilities, and vice versa.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/x86.c | 65 ++++++++++++++++++----------------------------
1 file changed, 25 insertions(+), 40 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ab3a4104febf..d2ab4da75783 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -880,31 +880,34 @@ int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
}
EXPORT_SYMBOL_GPL(kvm_set_xcr);

+#define __cr4_reserved_bits(__cpu_has, __c) \
+({ \
+ u64 __reserved_bits = CR4_RESERVED_BITS; \
+ \
+ if (!__cpu_has(__c, X86_FEATURE_XSAVE)) \
+ __reserved_bits |= X86_CR4_OSXSAVE; \
+ if (!__cpu_has(__c, X86_FEATURE_SMEP)) \
+ __reserved_bits |= X86_CR4_SMEP; \
+ if (!__cpu_has(__c, X86_FEATURE_SMAP)) \
+ __reserved_bits |= X86_CR4_SMAP; \
+ if (!__cpu_has(__c, X86_FEATURE_FSGSBASE)) \
+ __reserved_bits |= X86_CR4_FSGSBASE; \
+ if (!__cpu_has(__c, X86_FEATURE_PKU)) \
+ __reserved_bits |= X86_CR4_PKE; \
+ if (!__cpu_has(__c, X86_FEATURE_LA57)) \
+ __reserved_bits |= X86_CR4_LA57; \
+ __reserved_bits; \
+})
+
static u64 kvm_host_cr4_reserved_bits(struct cpuinfo_x86 *c)
{
- u64 reserved_bits = CR4_RESERVED_BITS;
+ u64 reserved_bits = __cr4_reserved_bits(cpu_has, c);

- if (!cpu_has(c, X86_FEATURE_XSAVE))
- reserved_bits |= X86_CR4_OSXSAVE;
+ if (cpuid_ecx(0x7) & bit(X86_FEATURE_LA57))
+ reserved_bits &= ~X86_CR4_LA57;

- if (!cpu_has(c, X86_FEATURE_SMEP))
- reserved_bits |= X86_CR4_SMEP;
-
- if (!cpu_has(c, X86_FEATURE_SMAP))
- reserved_bits |= X86_CR4_SMAP;
-
- if (!cpu_has(c, X86_FEATURE_FSGSBASE))
- reserved_bits |= X86_CR4_FSGSBASE;
-
- if (!cpu_has(c, X86_FEATURE_PKU))
- reserved_bits |= X86_CR4_PKE;
-
- if (!cpu_has(c, X86_FEATURE_LA57) &&
- !(cpuid_ecx(0x7) & bit(X86_FEATURE_LA57)))
- reserved_bits |= X86_CR4_LA57;
-
- if (!cpu_has(c, X86_FEATURE_UMIP) && !kvm_x86_ops->umip_emulated())
- reserved_bits |= X86_CR4_UMIP;
+ if (kvm_x86_ops->umip_emulated())
+ reserved_bits &= ~X86_CR4_UMIP;

return reserved_bits;
}
@@ -914,25 +917,7 @@ static int kvm_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
if (cr4 & cr4_reserved_bits)
return -EINVAL;

- if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) && (cr4 & X86_CR4_OSXSAVE))
- return -EINVAL;
-
- if (!guest_cpuid_has(vcpu, X86_FEATURE_SMEP) && (cr4 & X86_CR4_SMEP))
- return -EINVAL;
-
- if (!guest_cpuid_has(vcpu, X86_FEATURE_SMAP) && (cr4 & X86_CR4_SMAP))
- return -EINVAL;
-
- if (!guest_cpuid_has(vcpu, X86_FEATURE_FSGSBASE) && (cr4 & X86_CR4_FSGSBASE))
- return -EINVAL;
-
- if (!guest_cpuid_has(vcpu, X86_FEATURE_PKU) && (cr4 & X86_CR4_PKE))
- return -EINVAL;
-
- if (!guest_cpuid_has(vcpu, X86_FEATURE_LA57) && (cr4 & X86_CR4_LA57))
- return -EINVAL;
-
- if (!guest_cpuid_has(vcpu, X86_FEATURE_UMIP) && (cr4 & X86_CR4_UMIP))
+ if (cr4 & __cr4_reserved_bits(guest_cpuid_has, vcpu))
return -EINVAL;

return 0;
--
2.24.0