This patch removes CR4.LAM_SUP from cr4_reserved_bits to allows the
setting of X86_CR4_LAM_SUP by guest if the hardware platform supports
the feature.
The interception of CR4 is decided by CR4 guest/host mask and CR4 read
shadow.
The patch tiltle is not accurate.
On 2/9/2023 10:40 AM, Robert Hoo wrote:
Remove CR4.LAM_SUP (bit 28) from default CR4_RESERVED_BITS, while reserve
it in __cr4_reserved_bits() by feature testing.
Signed-off-by: Robert Hoo <robert.hu@xxxxxxxxxxxxxxx>
Reviewed-by: Jingqi Liu <jingqi.liu@xxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 3 ++-
arch/x86/kvm/x86.h | 2 ++
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f35f1ff4427b..4684896698f4 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -125,7 +125,8 @@
| X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR | X86_CR4_PCIDE \
| X86_CR4_OSXSAVE | X86_CR4_SMEP | X86_CR4_FSGSBASE \
| X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_VMXE \
- | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP))
+ | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP \
+ | X86_CR4_LAM_SUP))
#define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 9de72586f406..8ec5cc983062 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -475,6 +475,8 @@ bool kvm_msr_allowed(struct kvm_vcpu *vcpu, u32 index, u32 type);
__reserved_bits |= X86_CR4_VMXE; \
if (!__cpu_has(__c, X86_FEATURE_PCID)) \
__reserved_bits |= X86_CR4_PCIDE; \
+ if (!__cpu_has(__c, X86_FEATURE_LAM)) \
+ __reserved_bits |= X86_CR4_LAM_SUP; \
__reserved_bits; \
})
