[pve-devel] [PATCH kernel] Add MCE patch for Threadripper 3000 series compatibility

[Stefan Reiter]

A forum user reported that our kernel does not boot on Threadripper 3000
series CPUs, unless 'mce=off' is provided on the kernel commandline. [0]

This is a known issue, which has been fixed in mainline kernels and
backported to 5.4, 4.19 and 4.14 [1]. It is not, however, included in
5.3, nor in the Ubuntu builds. [2]

This patch is the original one posted for 5.5, which is the same as the
one ported to 5.4. It also applies cleanly to 5.3, and should work the
same, seeing as the backports to older versions do not have functional
changes either.

[0] https://forum.proxmox.com/threads/bug-pve-wont-boot-properly.63432/
[1] https://patchwork.kernel.org/project/linux-edac/list/?q=Allow+Reserved+types+to+be+overwritten+in+smca_banks
[2] https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/log/?qt=grep&q=Allow+Reserved+types+to+be+overwritten+in+smca_banks

Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
---

Not sure if we usually include fixes like that, but I feel like this could avoid
a lot of Forum threads once TR 3000 gets more commonplace :)


 ...w-Reserved-types-to-be-overwritten-i.patch | 88 +++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 patches/kernel/0006-x86-MCE-AMD-Allow-Reserved-types-to-be-overwritten-i.patch

diff --git a/patches/kernel/0006-x86-MCE-AMD-Allow-Reserved-types-to-be-overwritten-i.patch b/patches/kernel/0006-x86-MCE-AMD-Allow-Reserved-types-to-be-overwritten-i.patch
new file mode 100644
index 0000000..6f49ff6
--- /dev/null
+++ b/patches/kernel/0006-x86-MCE-AMD-Allow-Reserved-types-to-be-overwritten-i.patch
@@ -0,0 +1,88 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Yazen Ghannam <yazen.ghannam at amd.com>
+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 <yazen.ghannam at amd.com>
+Signed-off-by: Borislav Petkov <bp at suse.de>
+---
+ 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)) {
+-- 
+2.20.1
+
-- 
2.20.1