[PATCH v4 07/22] x86/mce/amd: Remove smca_banks_map

[Yazen Ghannam <yazen.ghannam@amd.com>]

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.
But it indicates neither which ones nor how many. Therefore, all the
registers are accessed and their bits are checked.

AMD systems generally enforce a Read-as-Zero/Writes-Ignored policy for
unused registers. Therefore, there is no harm to read an unused
register. This is already done in practice for most of the MCx_MISC
registers.

Remove the smca_banks_map variable as it is effectively redundant.

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/20250415-wip-mca-updates-v3-3-8ffd9eb4aa56@amd.com
    
    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 | 30 ------------------------------
 1 file changed, 30 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index f429451cafc8..0ffbee329a8c 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;
@@ -531,9 +504,6 @@ static u32 smca_get_block_address(unsigned int bank, unsigned int block,
 	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);
 }
 

-- 
2.49.0