[PATCH v4 15/15] x86/msr: Change the function type of native_read_msr_safe()

Xin Li (Intel)
2025-04-27T09:21:51Z

Modify the function type of native_read_msr_safe() to:

int native_read_msr_safe(u32 msr, u64 *val)

This change makes the function return an error code instead of the
MSR value, aligning it with the type of native_write_msr_safe().
Consequently, their callers can check the results in the same way.

While at it, convert leftover MSR data type "unsigned int" to u32.

Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/msr.h | 21 +++++++++++----------
arch/x86/include/asm/paravirt.h | 19 ++++++++-----------
arch/x86/include/asm/paravirt_types.h | 6 +++---
arch/x86/kvm/svm/svm.c | 19 +++++++------------
arch/x86/xen/enlighten_pv.c | 13 ++++++++-----
arch/x86/xen/pmu.c | 14 ++++++++------
6 files changed, 45 insertions(+), 47 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 0392b9596107..e7ee51ccd82e 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -130,18 +130,22 @@ static inline u64 native_read_msr(u32 msr)
return val;
}

-static inline u64 native_read_msr_safe(u32 msr, int *err)
+static inline int native_read_msr_safe(u32 msr, u64 *p)
{
+ int err;
DECLARE_ARGS(val, low, high);

asm volatile("1: rdmsr ; xor %[err],%[err]\n"
"2:\n\t"
_ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_RDMSR_SAFE, %[err])
- : [err] "=r" (*err), EAX_EDX_RET(val, low, high)
+ : [err] "=r" (err), EAX_EDX_RET(val, low, high)
: "c" (msr));
if (tracepoint_enabled(read_msr))
- do_trace_read_msr(msr, EAX_EDX_VAL(val, low, high), *err);
- return EAX_EDX_VAL(val, low, high);
+ do_trace_read_msr(msr, EAX_EDX_VAL(val, low, high), err);
+
+ *p = EAX_EDX_VAL(val, low, high);
+
+ return err;
}

/* Can be uninlined because referenced by paravirt */
@@ -221,8 +225,8 @@ static inline int wrmsrq_safe(u32 msr, u64 val)
/* rdmsr with exception handling */
#define rdmsr_safe(msr, low, high) \
({ \
- int __err; \
- u64 __val = native_read_msr_safe((msr), &__err); \
+ u64 __val; \
+ int __err = native_read_msr_safe((msr), &__val); \
(*low) = (u32)__val; \
(*high) = (u32)(__val >> 32); \
__err; \
@@ -230,10 +234,7 @@ static inline int wrmsrq_safe(u32 msr, u64 val)

static inline int rdmsrq_safe(u32 msr, u64 *p)
{
- int err;
-
- *p = native_read_msr_safe(msr, &err);
- return err;
+ return native_read_msr_safe(msr, p);
}

static __always_inline u64 rdpmc(int counter)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index edf23bde367e..03f680d1057a 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -175,7 +175,7 @@ static inline void __write_cr4(unsigned long x)
PVOP_VCALL1(cpu.write_cr4, x);
}

-static inline u64 paravirt_read_msr(unsigned msr)
+static inline u64 paravirt_read_msr(u32 msr)
{
return PVOP_CALL1(u64, cpu.read_msr, msr);
}
@@ -185,9 +185,9 @@ static inline void paravirt_write_msr(u32 msr, u64 val)
PVOP_VCALL2(cpu.write_msr, msr, val);
}

-static inline u64 paravirt_read_msr_safe(unsigned msr, int *err)
+static inline int paravirt_read_msr_safe(u32 msr, u64 *val)
{
- return PVOP_CALL2(u64, cpu.read_msr_safe, msr, err);
+ return PVOP_CALL2(int, cpu.read_msr_safe, msr, val);
}

static inline int paravirt_write_msr_safe(u32 msr, u64 val)
@@ -225,19 +225,16 @@ static inline int wrmsrq_safe(u32 msr, u64 val)
/* rdmsr with exception handling */
#define rdmsr_safe(msr, a, b) \
({ \
- int _err; \
- u64 _l = paravirt_read_msr_safe(msr, &_err); \
+ u64 _l; \
+ int _err = paravirt_read_msr_safe((msr), &_l); \
(*a) = (u32)_l; \
- (*b) = _l >> 32; \
+ (*b) = (u32)(_l >> 32); \
_err; \
})

-static inline int rdmsrq_safe(unsigned msr, u64 *p)
+static __always_inline int rdmsrq_safe(u32 msr, u64 *p)
{
- int err;
-
- *p = paravirt_read_msr_safe(msr, &err);
- return err;
+ return paravirt_read_msr_safe(msr, p);
}

static __always_inline u64 rdpmc(int counter)
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 78777b78da12..b08b9d3122d6 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -91,14 +91,14 @@ struct pv_cpu_ops {
unsigned int *ecx, unsigned int *edx);

/* Unsafe MSR operations. These will warn or panic on failure. */
- u64 (*read_msr)(unsigned int msr);
+ u64 (*read_msr)(u32 msr);
void (*write_msr)(u32 msr, u64 val);

/*
* Safe MSR operations.
- * read sets err to 0 or -EIO. write returns 0 or -EIO.
+ * Returns 0 or -EIO.
*/
- u64 (*read_msr_safe)(unsigned int msr, int *err);
+ int (*read_msr_safe)(u32 msr, u64 *val);
int (*write_msr_safe)(u32 msr, u64 val);

u64 (*read_pmc)(int counter);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 4ef9978dce70..838606f784c9 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -475,15 +475,13 @@ static void svm_inject_exception(struct kvm_vcpu *vcpu)

static void svm_init_erratum_383(void)
{
- int err;
u64 val;

if (!static_cpu_has_bug(X86_BUG_AMD_TLB_MMATCH))
return;

/* Use _safe variants to not break nested virtualization */
- val = native_read_msr_safe(MSR_AMD64_DC_CFG, &err);
- if (err)
+ if (native_read_msr_safe(MSR_AMD64_DC_CFG, &val))
return;

val |= (1ULL << 47);
@@ -648,13 +646,12 @@ static int svm_enable_virtualization_cpu(void)
* erratum is present everywhere).
*/
if (cpu_has(&boot_cpu_data, X86_FEATURE_OSVW)) {
- uint64_t len, status = 0;
+ u64 len, status = 0;
int err;

- len = native_read_msr_safe(MSR_AMD64_OSVW_ID_LENGTH, &err);
+ err = native_read_msr_safe(MSR_AMD64_OSVW_ID_LENGTH, &len);
if (!err)
- status = native_read_msr_safe(MSR_AMD64_OSVW_STATUS,
- &err);
+ err = native_read_msr_safe(MSR_AMD64_OSVW_STATUS, &status);

if (err)
osvw_status = osvw_len = 0;
@@ -2145,14 +2142,13 @@ static int ac_interception(struct kvm_vcpu *vcpu)

static bool is_erratum_383(void)
{
- int err, i;
+ int i;
u64 value;

if (!erratum_383_found)
return false;

- value = native_read_msr_safe(MSR_IA32_MC0_STATUS, &err);
- if (err)
+ if (native_read_msr_safe(MSR_IA32_MC0_STATUS, &value))
return false;

/* Bit 62 may or may not be set for this mce */
@@ -2165,8 +2161,7 @@ static bool is_erratum_383(void)
for (i = 0; i < 6; ++i)
native_write_msr_safe(MSR_IA32_MCx_STATUS(i), 0);

- value = native_read_msr_safe(MSR_IA32_MCG_STATUS, &err);
- if (!err) {
+ if (!native_read_msr_safe(MSR_IA32_MCG_STATUS, &value)) {
value &= ~(1ULL << 2);
native_write_msr_safe(MSR_IA32_MCG_STATUS, value);
}
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index c067d1e8a39c..0b2f5e679026 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1086,7 +1086,7 @@ static void xen_write_cr4(unsigned long cr4)
native_write_cr4(cr4);
}

-static u64 xen_do_read_msr(unsigned int msr, int *err)
+static u64 xen_do_read_msr(u32 msr, int *err)
{
u64 val = 0; /* Avoid uninitialized value for safe variant. */

@@ -1094,7 +1094,7 @@ static u64 xen_do_read_msr(unsigned int msr, int *err)
return val;

if (err)
- val = native_read_msr_safe(msr, err);
+ *err = native_read_msr_safe(msr, &val);
else
val = native_read_msr(msr);

@@ -1159,9 +1159,12 @@ static void xen_do_write_msr(u32 msr, u64 val, int *err)
}
}

-static u64 xen_read_msr_safe(unsigned int msr, int *err)
+static int xen_read_msr_safe(u32 msr, u64 *val)
{
- return xen_do_read_msr(msr, err);
+ int err;
+
+ *val = xen_do_read_msr(msr, &err);
+ return err;
}

static int xen_write_msr_safe(u32 msr, u64 val)
@@ -1173,7 +1176,7 @@ static int xen_write_msr_safe(u32 msr, u64 val)
return err;
}

-static u64 xen_read_msr(unsigned int msr)
+static u64 xen_read_msr(u32 msr)
{
int err;

diff --git a/arch/x86/xen/pmu.c b/arch/x86/xen/pmu.c
index 5f3d2a6c70f1..d308147cd368 100644
--- a/arch/x86/xen/pmu.c
+++ b/arch/x86/xen/pmu.c
@@ -318,11 +318,12 @@ static u64 xen_amd_read_pmc(int counter)
uint8_t xenpmu_flags = get_xenpmu_flags();

if (!xenpmu_data || !(xenpmu_flags & XENPMU_IRQ_PROCESSING)) {
- uint32_t msr;
- int err;
+ u32 msr;
+ u64 val;

msr = amd_counters_base + (counter * amd_msr_step);
- return native_read_msr_safe(msr, &err);
+ native_read_msr_safe(msr, &val);
+ return val;
}

ctxt = &xenpmu_data->pmu.c.amd;
@@ -339,15 +340,16 @@ static u64 xen_intel_read_pmc(int counter)
uint8_t xenpmu_flags = get_xenpmu_flags();

if (!xenpmu_data || !(xenpmu_flags & XENPMU_IRQ_PROCESSING)) {
- uint32_t msr;
- int err;
+ u32 msr;
+ u64 val;

if (counter & (1 << INTEL_PMC_TYPE_SHIFT))
msr = MSR_CORE_PERF_FIXED_CTR0 + (counter & 0xffff);
else
msr = MSR_IA32_PERFCTR0 + counter;

- return native_read_msr_safe(msr, &err);
+ native_read_msr_safe(msr, &val);
+ return val;
}

ctxt = &xenpmu_data->pmu.c.intel;
--
2.49.0