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- From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
- From: Yazen Ghannam <[email protected]>
- Date: Thu, 21 Nov 2019 08:15:08 -0600
- Subject: [PATCH] x86/MCE/AMD: Allow Reserved types to be overwritten in
- smca_banks[]
- Each logical CPU in Scalable MCA systems controls a unique set of MCA
- banks in the system. These banks are not shared between CPUs. The bank
- types and ordering will be the same across CPUs on currently available
- systems.
- However, some CPUs may see a bank as Reserved/Read-as-Zero (RAZ) while
- other CPUs do not. In this case, the bank seen as Reserved on one CPU is
- assumed to be the same type as the bank seen as a known type on another
- CPU.
- In general, this occurs when the hardware represented by the MCA bank
- is disabled, e.g. disabled memory controllers on certain models, etc.
- The MCA bank is disabled in the hardware, so there is no possibility of
- getting an MCA/MCE from it even if it is assumed to have a known type.
- For example:
- Full system:
- Bank | Type seen on CPU0 | Type seen on CPU1
- ------------------------------------------------
- 0 | LS | LS
- 1 | UMC | UMC
- 2 | CS | CS
- System with hardware disabled:
- Bank | Type seen on CPU0 | Type seen on CPU1
- ------------------------------------------------
- 0 | LS | LS
- 1 | UMC | RAZ
- 2 | CS | CS
- For this reason, there is a single, global struct smca_banks[] that is
- initialized at boot time. This array is initialized on each CPU as it
- comes online. However, the array will not be updated if an entry already
- exists.
- This works as expected when the first CPU (usually CPU0) has all
- possible MCA banks enabled. But if the first CPU has a subset, then it
- will save a "Reserved" type in smca_banks[]. Successive CPUs will then
- not be able to update smca_banks[] even if they encounter a known bank
- type.
- This may result in unexpected behavior. Depending on the system
- configuration, a user may observe issues enumerating the MCA
- thresholding sysfs interface. The issues may be as trivial as sysfs
- entries not being available, or as severe as system hangs.
- For example:
- Bank | Type seen on CPU0 | Type seen on CPU1
- ------------------------------------------------
- 0 | LS | LS
- 1 | RAZ | UMC
- 2 | CS | CS
- Extend the smca_banks[] entry check to return if the entry is a
- non-reserved type. Otherwise, continue so that CPUs that encounter a
- known bank type can update smca_banks[].
- Fixes: 68627a697c19 ("x86/mce/AMD, EDAC/mce_amd: Enumerate Reserved SMCA bank type")
- Signed-off-by: Yazen Ghannam <[email protected]>
- Signed-off-by: Borislav Petkov <[email protected]>
- Signed-off-by: Thomas Lamprecht <[email protected]>
- ---
- arch/x86/kernel/cpu/mce/amd.c | 2 +-
- 1 file changed, 1 insertion(+), 1 deletion(-)
- diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
- index 6ea7fdc82f3c..08e09c8c269f 100644
- --- a/arch/x86/kernel/cpu/mce/amd.c
- +++ b/arch/x86/kernel/cpu/mce/amd.c
- @@ -266,7 +266,7 @@ static void smca_configure(unsigned int bank, unsigned int cpu)
- smca_set_misc_banks_map(bank, cpu);
-
- /* Return early if this bank was already initialized. */
- - if (smca_banks[bank].hwid)
- + if (smca_banks[bank].hwid && smca_banks[bank].hwid->hwid_mcatype != 0)
- return;
-
- if (rdmsr_safe_on_cpu(cpu, MSR_AMD64_SMCA_MCx_IPID(bank), &low, &high)) {
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