[PATCH v7 4/8] x86/mce/amd: Support SMCA Corrected Error Interrupt

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

AMD systems optionally support MCA thresholding which provides the
ability for hardware to send an interrupt when a set error threshold is
reached. This feature counts errors of all severities, but it is
commonly used to report correctable errors with an interrupt rather than
polling.

Scalable MCA systems allow the Platform to take control of this feature.
In this case, the OS will not see the feature configuration and control
bits in the MCA_MISC* registers. The OS will not receive the MCA
thresholding interrupt, and it will need to poll for correctable errors.

A "corrected error interrupt" will be available on Scalable MCA systems.
This will be used in the same configuration where the Platform controls
MCA thresholding. However, the Platform will now be able to send the
MCA thresholding interrupt to the OS.

Check for, and enable, this feature during per-CPU SMCA init.

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/20250908-wip-mca-updates-v6-11-eef5d6c74b9c@amd.com
    
    v6->v7:
    * No change.
    
    v5->v6:
    * No change.
    
    v4->v5:
    * No change.
    
    v3->v4:
    * Add code comment describing bits.
    
    v2->v3:
    * Add tags from Tony.
    
    v1->v2:
    * Use new per-CPU struct.

 arch/x86/kernel/cpu/mce/amd.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index 3bbf2ecf71b6..91af769b9d8a 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -308,6 +308,23 @@ static void smca_configure(unsigned int bank, unsigned int cpu)
 			high |= BIT(5);
 		}
 
+		/*
+		 * SMCA Corrected Error Interrupt
+		 *
+		 * MCA_CONFIG[IntPresent] is bit 10, and tells us if the bank can
+		 * send an MCA Thresholding interrupt without the OS initializing
+		 * this feature. This can be used if the threshold limit is managed
+		 * by the platform.
+		 *
+		 * MCA_CONFIG[IntEn] is bit 40 (8 in the high portion of the MSR).
+		 * The OS should set this to inform the platform that the OS is ready
+		 * to handle the MCA Thresholding interrupt.
+		 */
+		if ((low & BIT(10)) && data->thr_intr_en) {
+			__set_bit(bank, data->thr_intr_banks);
+			high |= BIT(8);
+		}
+
 		this_cpu_ptr(mce_banks_array)[bank].lsb_in_status = !!(low & BIT(8));
 
 		wrmsr(smca_config, low, high);

-- 
2.51.0