Commit b0563468 authored by Andrew Cooper's avatar Andrew Cooper Committed by Borislav Petkov (AMD)
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x86/CPU/AMD: Disable XSAVES on AMD family 0x17 



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: default avatarTavis Ormandy <taviso@gmail.com>
Signed-off-by: default avatarAndrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20230307174643.1240184-1-andrew.cooper3@citrix.com
parent fe15c26e

arch/x86/kernel/cpu/amd.c

+9 −0
Original line number Diff line number Diff line
@@ -880,6 +880,15 @@ void init_spectral_chicken(struct cpuinfo_x86 *c) 
		}

	}

#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);

}



static void init_amd_zn(struct cpuinfo_x86 *c)