[PATCH v7 2/7] x86/cpu, kvm: Add the NO_NESTED_DATA_BP feature

Kim Phillips
2023-01-16T23:03:00Z

The "Processor ignores nested data breakpoints" feature was being
open-coded for KVM in __do_cpuid_func(). Add it to its newly added
CPUID leaf 0x80000021 EAX proper, and propagate it in kvm_set_cpu_caps()
instead.

Also drop the bit description comments now it's more self-describing.

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
---
arch/x86/include/asm/cpufeatures.h | 3 +++
arch/x86/kvm/cpuid.c | 8 ++++++--
2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index a84536876794..8255b95a7987 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -428,6 +428,9 @@
#define X86_FEATURE_V_TSC_AUX (19*32+ 9) /* "" Virtual TSC_AUX */
#define X86_FEATURE_SME_COHERENT (19*32+10) /* "" AMD hardware-enforced cache coherency */

+/* AMD-defined Extended Feature 2 EAX, CPUID level 0x80000021 (EAX), word 20 */
+#define X86_FEATURE_NO_NESTED_DATA_BP (20*32+ 0) /* "" AMD No Nested Data Breakpoints */
+
/*
* BUG word(s)
*/
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 596061c1610e..c9081e3a1b66 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -741,6 +741,10 @@ void kvm_set_cpu_caps(void)
0 /* SME */ | F(SEV) | 0 /* VM_PAGE_FLUSH */ | F(SEV_ES) |
F(SME_COHERENT));

+ kvm_cpu_cap_mask(CPUID_8000_0021_EAX,
+ F(NO_NESTED_DATA_BP)
+ );
+
kvm_cpu_cap_mask(CPUID_C000_0001_EDX,
F(XSTORE) | F(XSTORE_EN) | F(XCRYPT) | F(XCRYPT_EN) |
F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) |
@@ -1222,9 +1226,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
break;
case 0x80000021:
entry->ebx = entry->ecx = entry->edx = 0;
+ cpuid_entry_override(entry, CPUID_8000_0021_EAX);
/*
* Pass down these bits:
- * EAX 0 NNDBP, Processor ignores nested data breakpoints
* EAX 2 LAS, LFENCE always serializing
* EAX 6 NSCB, Null selector clear base
*
@@ -1235,7 +1239,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
* KVM doesn't support SMM_CTL.
* EAX 9 SMM_CTL MSR is not supported
*/
- entry->eax &= BIT(0) | BIT(2) | BIT(6);
+ entry->eax &= BIT(2) | BIT(6);
entry->eax |= BIT(9);
if (static_cpu_has(X86_FEATURE_LFENCE_RDTSC))
entry->eax |= BIT(2);
--
2.34.1