Patch "x86/CPU/AMD: Disable XSAVES on AMD family 0x17" has been added to the 4.14-stable tree

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This is a note to let you know that I've just added the patch titled

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

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-cpu-amd-disable-xsaves-on-amd-family-0x17.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From b0563468eeac88ebc70559d52a0b66efc37e4e9d Mon Sep 17 00:00:00 2001
From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Date: Tue, 7 Mar 2023 17:46:43 +0000
Subject: x86/CPU/AMD: Disable XSAVES on AMD family 0x17

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
@@ -197,6 +197,15 @@ 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);
 }
 
 static void init_amd_k7(struct cpuinfo_x86 *c)


Patches currently in stable-queue which might be from andrew.cooper3@xxxxxxxxxx are

queue-4.14/x86-cpu-amd-disable-xsaves-on-amd-family-0x17.patch



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