The MCx_MISC0[BlkPtr] field was used on legacy systems to hold a
register offset for the next MCx_MISC* register. In this way, an
implementation-specific number of registers can be discovered at
runtime.
The MCAX/SMCA register space simplifies this by always including
the MCx_MISC[1-4] registers. The MCx_MISC0[BlkPtr] field is used to
indicate (true/false) whether any MCx_MISC[1-4] registers are present.
Currently, MCx_MISC0[BlkPtr] is checked early and cached to be used
during sysfs init later. This is unnecessary as the MCx_MISC0 register
is read again later anyway.
Remove the smca_banks_map variable as it is effectively redundant, and
use a direct register/bit check instead.
Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
---
Notes:
Link:
https://lore.kernel.org/r/20250624-wip-mca-updates-v4-7-236dd74f645f@amd.com
v4->v5:
* Keep MCx_MISC0[BlkPtr] check to be compliant with uarch.
v3->v4:
* No change.
v2->v3:
* Minor edit in commit message.
* Added tags from Qiuxu and Tony.
v1->v2:
* New in v2.
arch/x86/kernel/cpu/mce/amd.c | 34 +++-------------------------------
1 file changed, 3 insertions(+), 31 deletions(-)
diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index f429451cafc8..580682af432d 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -252,9 +252,6 @@ static DEFINE_PER_CPU(struct threshold_bank **, threshold_banks);
*/
static DEFINE_PER_CPU(u64, bank_map);
-/* Map of banks that have more than MCA_MISC0 available. */
-static DEFINE_PER_CPU(u64, smca_misc_banks_map);
-
static void amd_threshold_interrupt(void);
static void amd_deferred_error_interrupt(void);
@@ -264,28 +261,6 @@ static void default_deferred_error_interrupt(void)
}
void (*deferred_error_int_vector)(void) = default_deferred_error_interrupt;
-static void smca_set_misc_banks_map(unsigned int bank, unsigned int cpu)
-{
- u32 low, high;
-
- /*
- * For SMCA enabled processors, BLKPTR field of the first MISC register
- * (MCx_MISC0) indicates presence of additional MISC regs set (MISC1-4).
- */
- if (rdmsr_safe(MSR_AMD64_SMCA_MCx_CONFIG(bank), &low, &high))
- return;
-
- if (!(low & MCI_CONFIG_MCAX))
- return;
-
- if (rdmsr_safe(MSR_AMD64_SMCA_MCx_MISC(bank), &low, &high))
- return;
-
- if (low & MASK_BLKPTR_LO)
- per_cpu(smca_misc_banks_map, cpu) |= BIT_ULL(bank);
-
-}
-
static void smca_configure(unsigned int bank, unsigned int cpu)
{
u8 *bank_counts = this_cpu_ptr(smca_bank_counts);
@@ -326,8 +301,6 @@ static void smca_configure(unsigned int bank, unsigned int cpu)
wrmsr(smca_config, low, high);
}
- smca_set_misc_banks_map(bank, cpu);
-
if (rdmsr_safe(MSR_AMD64_SMCA_MCx_IPID(bank), &low, &high)) {
pr_warn("Failed to read MCA_IPID for bank %d\n", bank);
return;
@@ -525,13 +498,12 @@ static void deferred_error_interrupt_enable(struct cpuinfo_x86 *c)
wrmsr(MSR_CU_DEF_ERR, low, high);
}
-static u32 smca_get_block_address(unsigned int bank, unsigned int block,
- unsigned int cpu)
+static u32 smca_get_block_address(unsigned int bank, unsigned int block, u32 low)
{
if (!block)
return MSR_AMD64_SMCA_MCx_MISC(bank);
- if (!(per_cpu(smca_misc_banks_map, cpu) & BIT_ULL(bank)))
+ if (!(low & MASK_BLKPTR_LO))
return 0;
return MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1);
@@ -547,7 +519,7 @@ static u32 get_block_address(u32 current_addr, u32 low, u32 high,
return addr;
if (mce_flags.smca)
- return smca_get_block_address(bank, block, cpu);
+ return smca_get_block_address(bank, block, low);
/* Fall back to method we used for older processors: */
switch (block) {
--
2.51.0On Mon, Aug 25, 2025 at 05:33:00PM +0000, Yazen Ghannam wrote:
> The MCx_MISC0[BlkPtr] field was used on legacy systems to hold a
> register offset for the next MCx_MISC* register. In this way, an
> implementation-specific number of registers can be discovered at
> runtime.
>
> The MCAX/SMCA register space simplifies this by always including
> the MCx_MISC[1-4] registers. The MCx_MISC0[BlkPtr] field is used to
> indicate (true/false) whether any MCx_MISC[1-4] registers are present.
>
> Currently, MCx_MISC0[BlkPtr] is checked early and cached to be used
> during sysfs init later. This is unnecessary as the MCx_MISC0 register
> is read again later anyway.
>
> Remove the smca_banks_map variable as it is effectively redundant, and
> use a direct register/bit check instead.
>
> Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
> Tested-by: Tony Luck <tony.luck@intel.com>
> Reviewed-by: Tony Luck <tony.luck@intel.com>
> Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
> ---
>
> Notes:
> Link:
> https://lore.kernel.org/r/20250624-wip-mca-updates-v4-7-236dd74f645f@amd.com
>
> v4->v5:
> * Keep MCx_MISC0[BlkPtr] check to be compliant with uarch.
I'm not sure I understand what that means...?
Anyway, some more cleanup ontop:
---
diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index 580682af432d..7e36bc0d0e6c 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -498,17 +498,6 @@ static void deferred_error_interrupt_enable(struct cpuinfo_x86 *c)
wrmsr(MSR_CU_DEF_ERR, low, high);
}
-static u32 smca_get_block_address(unsigned int bank, unsigned int block, u32 low)
-{
- if (!block)
- return MSR_AMD64_SMCA_MCx_MISC(bank);
-
- if (!(low & MASK_BLKPTR_LO))
- return 0;
-
- return MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1);
-}
-
static u32 get_block_address(u32 current_addr, u32 low, u32 high,
unsigned int bank, unsigned int block,
unsigned int cpu)
@@ -518,8 +507,15 @@ static u32 get_block_address(u32 current_addr, u32 low, u32 high,
if ((bank >= per_cpu(mce_num_banks, cpu)) || (block >= NR_BLOCKS))
return addr;
- if (mce_flags.smca)
- return smca_get_block_address(bank, block, low);
+ if (mce_flags.smca) {
+ if (!block)
+ return MSR_AMD64_SMCA_MCx_MISC(bank);
+
+ if (!(low & MASK_BLKPTR_LO))
+ return 0;
+
+ return MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1);
+ }
/* Fall back to method we used for older processors: */
switch (block) {
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On Mon, Aug 25, 2025 at 08:19:38PM +0200, Borislav Petkov wrote:
> On Mon, Aug 25, 2025 at 05:33:00PM +0000, Yazen Ghannam wrote:
> > The MCx_MISC0[BlkPtr] field was used on legacy systems to hold a
> > register offset for the next MCx_MISC* register. In this way, an
> > implementation-specific number of registers can be discovered at
> > runtime.
> >
> > The MCAX/SMCA register space simplifies this by always including
> > the MCx_MISC[1-4] registers. The MCx_MISC0[BlkPtr] field is used to
> > indicate (true/false) whether any MCx_MISC[1-4] registers are present.
> >
> > Currently, MCx_MISC0[BlkPtr] is checked early and cached to be used
> > during sysfs init later. This is unnecessary as the MCx_MISC0 register
> > is read again later anyway.
> >
> > Remove the smca_banks_map variable as it is effectively redundant, and
> > use a direct register/bit check instead.
> >
> > Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
> > Tested-by: Tony Luck <tony.luck@intel.com>
> > Reviewed-by: Tony Luck <tony.luck@intel.com>
> > Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
> > ---
> >
> > Notes:
> > Link:
> > https://lore.kernel.org/r/20250624-wip-mca-updates-v4-7-236dd74f645f@amd.com
> >
> > v4->v5:
> > * Keep MCx_MISC0[BlkPtr] check to be compliant with uarch.
>
> I'm not sure I understand what that means...?
I completely removed the check below in previous revisions. But I put
it back to make sure we follow the microarchitecture guidelines, i.e.
the procedure(s) in documentation (APM, PPR, etc.).
if (!(low & MASK_BLKPTR_LO))
return 0;
>
> Anyway, some more cleanup ontop:
>
> ---
> diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
> index 580682af432d..7e36bc0d0e6c 100644
> --- a/arch/x86/kernel/cpu/mce/amd.c
> +++ b/arch/x86/kernel/cpu/mce/amd.c
> @@ -498,17 +498,6 @@ static void deferred_error_interrupt_enable(struct cpuinfo_x86 *c)
> wrmsr(MSR_CU_DEF_ERR, low, high);
> }
>
> -static u32 smca_get_block_address(unsigned int bank, unsigned int block, u32 low)
> -{
> - if (!block)
> - return MSR_AMD64_SMCA_MCx_MISC(bank);
> -
> - if (!(low & MASK_BLKPTR_LO))
> - return 0;
> -
> - return MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1);
> -}
> -
> static u32 get_block_address(u32 current_addr, u32 low, u32 high,
> unsigned int bank, unsigned int block,
> unsigned int cpu)
> @@ -518,8 +507,15 @@ static u32 get_block_address(u32 current_addr, u32 low, u32 high,
> if ((bank >= per_cpu(mce_num_banks, cpu)) || (block >= NR_BLOCKS))
> return addr;
>
> - if (mce_flags.smca)
> - return smca_get_block_address(bank, block, low);
> + if (mce_flags.smca) {
> + if (!block)
> + return MSR_AMD64_SMCA_MCx_MISC(bank);
> +
> + if (!(low & MASK_BLKPTR_LO))
> + return 0;
> +
> + return MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1);
> + }
>
> /* Fall back to method we used for older processors: */
> switch (block) {
>
>
> --
Looks good to me.
Thanks,
Yazen
The following commit has been merged into the ras/core branch of tip:
Commit-ID: b249288abde5190bb113ea5acef8af4ceac4957c
Gitweb: https://git.kernel.org/tip/b249288abde5190bb113ea5acef8af4ceac4957c
Author: Yazen Ghannam <yazen.ghannam@amd.com>
AuthorDate: Mon, 25 Aug 2025 17:33:00
Committer: Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 05 Sep 2025 12:41:48 +02:00
x86/mce/amd: Remove smca_banks_map
The MCx_MISC0[BlkPtr] field was used on legacy systems to hold a register
offset for the next MCx_MISC* register. In this way, an implementation-specific
number of registers can be discovered at runtime.
The MCAX/SMCA register space simplifies this by always including the
MCx_MISC[1-4] registers. The MCx_MISC0[BlkPtr] field is used to indicate
(true/false) whether any MCx_MISC[1-4] registers are present.
Currently, MCx_MISC0[BlkPtr] is checked early and cached to be used during
sysfs init later. This is unnecessary as the MCx_MISC0 register is read again
later anyway.
Remove the smca_banks_map variable as it is effectively redundant, and use
a direct register/bit check instead.
[ bp: Zap smca_get_block_address() too. ]
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/20250825-wip-mca-updates-v5-3-865768a2eef8@amd.com
---
arch/x86/kernel/cpu/mce/amd.c | 50 ++++++----------------------------
1 file changed, 9 insertions(+), 41 deletions(-)
diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index f429451..7e36bc0 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -252,9 +252,6 @@ static DEFINE_PER_CPU(struct threshold_bank **, threshold_banks);
*/
static DEFINE_PER_CPU(u64, bank_map);
-/* Map of banks that have more than MCA_MISC0 available. */
-static DEFINE_PER_CPU(u64, smca_misc_banks_map);
-
static void amd_threshold_interrupt(void);
static void amd_deferred_error_interrupt(void);
@@ -264,28 +261,6 @@ static void default_deferred_error_interrupt(void)
}
void (*deferred_error_int_vector)(void) = default_deferred_error_interrupt;
-static void smca_set_misc_banks_map(unsigned int bank, unsigned int cpu)
-{
- u32 low, high;
-
- /*
- * For SMCA enabled processors, BLKPTR field of the first MISC register
- * (MCx_MISC0) indicates presence of additional MISC regs set (MISC1-4).
- */
- if (rdmsr_safe(MSR_AMD64_SMCA_MCx_CONFIG(bank), &low, &high))
- return;
-
- if (!(low & MCI_CONFIG_MCAX))
- return;
-
- if (rdmsr_safe(MSR_AMD64_SMCA_MCx_MISC(bank), &low, &high))
- return;
-
- if (low & MASK_BLKPTR_LO)
- per_cpu(smca_misc_banks_map, cpu) |= BIT_ULL(bank);
-
-}
-
static void smca_configure(unsigned int bank, unsigned int cpu)
{
u8 *bank_counts = this_cpu_ptr(smca_bank_counts);
@@ -326,8 +301,6 @@ static void smca_configure(unsigned int bank, unsigned int cpu)
wrmsr(smca_config, low, high);
}
- smca_set_misc_banks_map(bank, cpu);
-
if (rdmsr_safe(MSR_AMD64_SMCA_MCx_IPID(bank), &low, &high)) {
pr_warn("Failed to read MCA_IPID for bank %d\n", bank);
return;
@@ -525,18 +498,6 @@ static void deferred_error_interrupt_enable(struct cpuinfo_x86 *c)
wrmsr(MSR_CU_DEF_ERR, low, high);
}
-static u32 smca_get_block_address(unsigned int bank, unsigned int block,
- unsigned int cpu)
-{
- if (!block)
- return MSR_AMD64_SMCA_MCx_MISC(bank);
-
- if (!(per_cpu(smca_misc_banks_map, cpu) & BIT_ULL(bank)))
- return 0;
-
- return MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1);
-}
-
static u32 get_block_address(u32 current_addr, u32 low, u32 high,
unsigned int bank, unsigned int block,
unsigned int cpu)
@@ -546,8 +507,15 @@ static u32 get_block_address(u32 current_addr, u32 low, u32 high,
if ((bank >= per_cpu(mce_num_banks, cpu)) || (block >= NR_BLOCKS))
return addr;
- if (mce_flags.smca)
- return smca_get_block_address(bank, block, cpu);
+ if (mce_flags.smca) {
+ if (!block)
+ return MSR_AMD64_SMCA_MCx_MISC(bank);
+
+ if (!(low & MASK_BLKPTR_LO))
+ return 0;
+
+ return MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1);
+ }
/* Fall back to method we used for older processors: */
switch (block) {© 2016 - 2026 Red Hat, Inc.