linux-kernel - [PATCH] Revert "EDAC/mce_amd: Do not load edac_mce

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZPqQEHXgmak1LMNh@mattapan.m5p.com>
Date:   Thu, 7 Sep 2023 20:08:00 -0700
From:   Elliott Mitchell <ehem+xen@....com>
To:     smita.koralahallichannabasappa@....com
Cc:     linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, xen-devel@...ts.xenproject.org, rric@...nel.org,
        james.morse@....com, tony.luck@...el.com, yazen.ghannam@....com
Subject: [PATCH] Revert "EDAC/mce_amd: Do not load edac_mce_amd module on
 guests"

This reverts commit 767f4b620edadac579c9b8b6660761d4285fa6f9.

There are at least 3 valid reasons why a VM may see MCE events/registers.

First, the hypervisor may have a bug.  Ideally this should be dealt with
by fixing the hypervisor.  Failing that, the hypervisor and versions
effected need to be identified so only they are flagged as buggy.

Second, the Linux kernel may be handling adminstrative duties/hardware
for a hypervisor.  In this case, the events need to be processed and
potentially passed back through the hypervisor.

Third, the hypervisor may do full virtualization of MCE events.  In such
case, they should be handled normally.

Any of these blanket disabling the functionality is bad.  The original
patch was wrong.
---
 drivers/edac/mce_amd.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/edac/mce_amd.c b/drivers/edac/mce_amd.c
index 9215c06783df..1b7fccfbb654 100644
--- a/drivers/edac/mce_amd.c
+++ b/drivers/edac/mce_amd.c
@@ -1361,9 +1361,6 @@ static int __init mce_amd_init(void)
 	    c->x86_vendor != X86_VENDOR_HYGON)
 		return -ENODEV;

-	if (cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
-		return -ENODEV;
-
 	if (boot_cpu_has(X86_FEATURE_SMCA)) {
 		xec_mask = 0x3f;
 		goto out;
-- 
(\___(\___(\______          --=> 8-) EHM <=--          ______/)___/)___/)
 \BS (    |         ehem+sigmsg@....com  PGP 87145445         |    )   /
  \_CS\   |  _____  -O #include <stddisclaimer.h> O-   _____  |   /  _/
8A19\___\_|_/58D2 7E3D DDF4 7BA6 <-PGP-> 41D1 B375 37D0 8714\_|_/___/5445