This is a note to let you know that I've just added the patch titled x86/MCE/AMD: Allow Reserved types to be overwritten in smca_banks[] to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-mce-amd-allow-reserved-types-to-be-overwritten-in-smca_banks.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 966af20929ac24360ba3fac5533eb2ab003747da Mon Sep 17 00:00:00 2001 From: Yazen Ghannam <yazen.ghannam@xxxxxxx> Date: Thu, 21 Nov 2019 08:15:08 -0600 Subject: x86/MCE/AMD: Allow Reserved types to be overwritten in smca_banks[] From: Yazen Ghannam <yazen.ghannam@xxxxxxx> commit 966af20929ac24360ba3fac5533eb2ab003747da upstream. 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 <yazen.ghannam@xxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: linux-edac <linux-edac@xxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: x86-ml <x86@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20191121141508.141273-1-Yazen.Ghannam@xxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/cpu/mcheck/mce_amd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c @@ -228,7 +228,7 @@ static void smca_configure(unsigned int } /* 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(MSR_AMD64_SMCA_MCx_IPID(bank), &low, &high)) { Patches currently in stable-queue which might be from yazen.ghannam@xxxxxxx are queue-4.19/x86-mce-amd-allow-reserved-types-to-be-overwritten-in-smca_banks.patch queue-4.19/x86-mce-amd-do-not-use-rdmsr_safe_on_cpu-in-smca_configure.patch