On 15.03.2023 13:11, Greg Kroah-Hartman wrote:
From: Andrew Cooper andrew.cooper3@citrix.com
commit b0563468eeac88ebc70559d52a0b66efc37e4e9d upstream.
AMD Erratum 1386 is summarised as:
XSAVES Instruction May Fail to Save XMM Registers to the Provided State Save Area
This piece of accidental chronomancy causes the %xmm registers to occasionally reset back to an older value.
Ignore the XSAVES feature on all AMD Zen1/2 hardware. The XSAVEC instruction (which works fine) is equivalent on affected parts.
[ bp: Typos, move it into the F17h-specific function. ]
Reported-by: Tavis Ormandy taviso@gmail.com Signed-off-by: Andrew Cooper andrew.cooper3@citrix.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Cc: stable@kernel.org Link: https://lore.kernel.org/r/20230307174643.1240184-1-andrew.cooper3@citrix.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
arch/x86/kernel/cpu/amd.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -205,6 +205,15 @@ static void init_amd_k6(struct cpuinfo_x return; } #endif
- /*
* Work around Erratum 1386. The XSAVES instruction malfunctions in* certain circumstances on Zen1/2 uarch, and not all parts have had* updated microcode at the time of writing (March 2023).** Affected parts all have no supervisor XSAVE states, meaning that* the XSAVEC instruction (which works fine) is equivalent.*/- clear_cpu_cap(c, X86_FEATURE_XSAVES); }
This is essentially a well-intended NOP since K6 well predates XSAVES, and init_amd_k6() is *not* called for Zen CPUs.
This workaround should have been added to init_amd_zn() function instead.
4.19 and 4.14 backports of this patch have the same problem.
Thanks, Maciej