Commit e40c1e9d authored Mar 07, 2023 by Andrew Cooper Committed by Greg Kroah-Hartman Mar 17, 2023

x86/CPU/AMD: Disable XSAVES on AMD family 0x17



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>

parent 6631c8da

arch/x86/kernel/cpu/amd.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -205,6 +205,15 @@ static void init_amd_k6(struct cpuinfo_x86 *c)
		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);
		}

		static void init_amd_k7(struct cpuinfo_x86 *c)