793 Specific Combination of Writes to Write Combined Memory
Types and Locked Instructions May Cause Core Hang
Under a highly specific and detailed set of internal timing
conditions, a locked instruction may trigger a timing sequence whereby
the write to a write combined memory type is not flushed, causing the
locked instruction to stall indefinitely.
Potential Effect on System
Processor core hang.
BIOS should set MSRC001_1020 = 1b.
The vulnerability is applicable only to family 16h model 00h-0fh AMD
CPUs. Non-AMD CPUs are not vulnerable.
Red Hat would like to thank the Xen project for reporting this issue. Upstream acknowledges Jan Beulich as the original reporter.
This hardware issue is affecting certain AMD processors. Please consult your hardware vendor for any potential firmware updates providing a workaround for this issue.
Xen issued advisory:
Linux kernel proposed workaround:
It was noted that the previous fix was not sufficient for 32bit systems and also requires the following patch:
The advisory has further details.
This shouldn't affect our backport. No additional patch needed for rhel5.
This issue has been addressed in following products:
Red Hat Enterprise Linux 5
Via RHSA-2014:0285 https://rhn.redhat.com/errata/RHSA-2014-0285.html