[kvm-unit-tests PATCH v2 0/2] Fix testing failure in x86/msr

[kvm-unit-tests PATCH v2 0/2] Fix testing failure in x86/msr

[Mingwei Zhang]

Fixing failures in x86/msr for skylake on MSR_IA32_FLUSH_CMD. All code
suggested by Sean. Thanks for the help.

v1: https://lore.kernel.org/all/20240415172542.1830566-1-mizhang@google.com/


Mingwei Zhang (2):
  x86: Add FEP support on read/write register instructions
  x86: msr: testing MSR_IA32_FLUSH_CMD reserved bits only in KVM
    emulation

 lib/x86/desc.h      | 30 ++++++++++++++++++++++++------
 lib/x86/processor.h | 18 ++++++++++++++----
 x86/msr.c           | 17 +++++++++++++++--
 3 files changed, 53 insertions(+), 12 deletions(-)


base-commit: 7b0147ea57dc29ba844f5b60393a0639e55e88af
-- 
2.44.0.683.g7961c838ac-goog

[kvm-unit-tests PATCH v2 1/2] x86: Add FEP support on read/write register instructions

[Mingwei Zhang]

Add FEP support on read/write register instructions to enable testing rdmsr
and wrmsr when force emulation is turned on.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
---
 lib/x86/desc.h      | 30 ++++++++++++++++++++++++------
 lib/x86/processor.h | 18 ++++++++++++++----
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index 7778a0f8..92c45a48 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -272,9 +272,9 @@ extern gdt_entry_t *get_tss_descr(void);
 extern unsigned long get_gdt_entry_base(gdt_entry_t *entry);
 extern unsigned long get_gdt_entry_limit(gdt_entry_t *entry);
 
-#define asm_safe(insn, inputs...)					\
+#define __asm_safe(fep, insn, inputs...)				\
 ({									\
-	asm volatile(ASM_TRY("1f")					\
+	asm volatile(__ASM_TRY(fep, "1f")				\
 		     insn "\n\t"					\
 		     "1:\n\t"						\
 		     :							\
@@ -283,9 +283,15 @@ extern unsigned long get_gdt_entry_limit(gdt_entry_t *entry);
 	exception_vector();						\
 })
 
-#define asm_safe_out1(insn, output, inputs...)				\
+#define asm_safe(insn, inputs...)					\
+	__asm_safe("", insn, inputs)
+
+#define asm_fep_safe(insn, output, inputs...)				\
+	__asm_safe_out1(KVM_FEP, insn, output, inputs)
+
+#define __asm_safe_out1(fep, insn, output, inputs...)			\
 ({									\
-	asm volatile(ASM_TRY("1f")					\
+	asm volatile(__ASM_TRY(fep, "1f")				\
 		     insn "\n\t"					\
 		     "1:\n\t"						\
 		     : output						\
@@ -294,9 +300,15 @@ extern unsigned long get_gdt_entry_limit(gdt_entry_t *entry);
 	exception_vector();						\
 })
 
-#define asm_safe_out2(insn, output1, output2, inputs...)		\
+#define asm_safe_out1(insn, output, inputs...)				\
+	__asm_safe_out1("", insn, output, inputs)
+
+#define asm_fep_safe_out1(insn, output, inputs...)			\
+	__asm_safe_out1(KVM_FEP, insn, output, inputs)
+
+#define __asm_safe_out2(fep, insn, output1, output2, inputs...)		\
 ({									\
-	asm volatile(ASM_TRY("1f")					\
+	asm volatile(__ASM_TRY(fep, "1f")				\
 		     insn "\n\t"					\
 		     "1:\n\t"						\
 		     : output1, output2					\
@@ -305,6 +317,12 @@ extern unsigned long get_gdt_entry_limit(gdt_entry_t *entry);
 	exception_vector();						\
 })
 
+#define asm_safe_out2(fep, insn, output1, output2, inputs...)		\
+	__asm_safe_out2("", insn, output1, output2, inputs)
+
+#define asm_fep_safe_out2(insn, output1, output2, inputs...)		\
+	__asm_safe_out2(KVM_FEP, insn, output1, output2, inputs)
+
 #define __asm_safe_report(want, insn, inputs...)			\
 do {									\
 	int vector = asm_safe(insn, inputs);				\
diff --git a/lib/x86/processor.h b/lib/x86/processor.h
index 44f4fd1e..d20496c0 100644
--- a/lib/x86/processor.h
+++ b/lib/x86/processor.h
@@ -430,12 +430,12 @@ static inline void wrmsr(u32 index, u64 val)
 	asm volatile ("wrmsr" : : "a"(a), "d"(d), "c"(index) : "memory");
 }
 
-#define rdreg64_safe(insn, index, val)					\
+#define __rdreg64_safe(fep, insn, index, val)				\
 ({									\
 	uint32_t a, d;							\
 	int vector;							\
 									\
-	vector = asm_safe_out2(insn, "=a"(a), "=d"(d), "c"(index));	\
+	vector = __asm_safe_out2(fep, insn, "=a"(a), "=d"(d), "c"(index));\
 									\
 	if (vector)							\
 		*(val) = 0;						\
@@ -444,13 +444,18 @@ static inline void wrmsr(u32 index, u64 val)
 	vector;								\
 })
 
-#define wrreg64_safe(insn, index, val)					\
+#define rdreg64_safe(insn, index, val)					\
+	__rdreg64_safe("", insn, index, val)
+
+#define __wrreg64_safe(fep, insn, index, val)				\
 ({									\
 	uint32_t eax = (val), edx = (val) >> 32;			\
 									\
-	asm_safe(insn, "a" (eax), "d" (edx), "c" (index));		\
+	__asm_safe(fep, insn, "a" (eax), "d" (edx), "c" (index));	\
 })
 
+#define wrreg64_safe(insn, index, val)					\
+	__wrreg64_safe("", insn, index, val)
 
 static inline int rdmsr_safe(u32 index, uint64_t *val)
 {
@@ -462,6 +467,11 @@ static inline int wrmsr_safe(u32 index, u64 val)
 	return wrreg64_safe("wrmsr", index, val);
 }
 
+static inline int wrmsr_fep_safe(u32 index, u64 val)
+{
+	return __wrreg64_safe(KVM_FEP, "wrmsr", index, val);
+}
+
 static inline int rdpmc_safe(u32 index, uint64_t *val)
 {
 	return rdreg64_safe("rdpmc", index, val);
-- 
2.44.0.683.g7961c838ac-goog

[kvm-unit-tests PATCH v2 2/2] x86: msr: testing MSR_IA32_FLUSH_CMD reserved bits only in KVM emulation

[Mingwei Zhang]

Avoid testing reserved bits of MSR_IA32_FLUSH_CMD in hardware. Since KVM
passes through the MSR at runtime, testing reserved bits directly on the HW
does not generate #GP in some older CPU models like skylake.

Ideally, it could be fixed by enumerating all such CPU models. The value
added is would be low. So just focus on testing bits when the KVM force
emulation is enabled. This is in a new helper test_wrmsr_fep_fault().

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
---
 x86/msr.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/x86/msr.c b/x86/msr.c
index 3a041fab..17f93029 100644
--- a/x86/msr.c
+++ b/x86/msr.c
@@ -112,6 +112,16 @@ static void test_rdmsr_fault(u32 msr, const char *name)
 	       "Expected #GP on RDSMR(%s), got vector %d", name, vector);
 }
 
+static void test_wrmsr_fep_fault(u32 msr, const char *name,
+				 unsigned long long val)
+{
+	unsigned char vector = wrmsr_fep_safe(msr, val);
+
+	report(vector == GP_VECTOR,
+	       "Expected #GP on emulated WRSMR(%s, 0x%llx), got vector %d",
+	       name, val, vector);
+}
+
 static void test_msr(struct msr_info *msr, bool is_64bit_host)
 {
 	if (is_64bit_host || !msr->is_64bit_only) {
@@ -302,8 +312,11 @@ static void test_cmd_msrs(void)
 		test_wrmsr_fault(MSR_IA32_FLUSH_CMD, "FLUSH_CMD", 0);
 		test_wrmsr_fault(MSR_IA32_FLUSH_CMD, "FLUSH_CMD", L1D_FLUSH);
 	}
-	for (i = 1; i < 64; i++)
-		test_wrmsr_fault(MSR_IA32_FLUSH_CMD, "FLUSH_CMD", BIT_ULL(i));
+
+	if (is_fep_available()) {
+		for (i = 1; i < 64; i++)
+			test_wrmsr_fep_fault(MSR_IA32_FLUSH_CMD, "FLUSH_CMD", BIT_ULL(i));
+	}
 }
 
 int main(int ac, char **av)
-- 
2.44.0.683.g7961c838ac-goog

Re: [kvm-unit-tests PATCH v2 0/2] Fix testing failure in x86/msr

[Mingwei Zhang]

On Wed, Apr 17, 2024, Mingwei Zhang wrote:
> Fixing failures in x86/msr for skylake on MSR_IA32_FLUSH_CMD. All code
> suggested by Sean. Thanks for the help.
> 

gentle ping on this?

> v1: https://lore.kernel.org/all/20240415172542.1830566-1-mizhang@google.com/
> 
> 
> Mingwei Zhang (2):
>   x86: Add FEP support on read/write register instructions
>   x86: msr: testing MSR_IA32_FLUSH_CMD reserved bits only in KVM
>     emulation
> 
>  lib/x86/desc.h      | 30 ++++++++++++++++++++++++------
>  lib/x86/processor.h | 18 ++++++++++++++----
>  x86/msr.c           | 17 +++++++++++++++--
>  3 files changed, 53 insertions(+), 12 deletions(-)
> 
> 
> base-commit: 7b0147ea57dc29ba844f5b60393a0639e55e88af
> -- 
> 2.44.0.683.g7961c838ac-goog
>