Re: [PATCH 5.4 02/68] x86/CPU/AMD: Disable XSAVES on AMD family 0x17

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 15.03.2023 13:11, Greg Kroah-Hartman wrote:
From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230307174643.1240184-1-andrew.cooper3@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
  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




[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux