linux-kernel - Re: Stable linux-5.10.x regression triggered by MDS mitigation

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Date: Tue, 25 Jun 2024 13:49:17 +0000
From: Jari Ruusu <jariruusu@...tonmail.com>
To: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Stable linux-5.10.x regression triggered by MDS mitigation

On Monday, June 24th, 2024 at 20:09, Pawan Gupta <pawan.kumar.gupta@...ux.intel.com> wrote:
> Below patch (for v6.10-rc5) should fix this. I didn't send this patch
> earlier because I havn't got a chance to make sure if it will work for
> other cases like modify_ldt().

Thank you for fixing this regression.

I tested your patch on 32-bit linux-5.10.220 inside VM, and now
dosemu seems to work OK.

I do have a related question:
In SYSENTER code path (that is not used by virtual-8086 mode),
there is CLEAR_CPU_BUFFERS just before STI and SYSEXIT, but that
CLEAR_CPU_BUFFERS happens after flags are restored with POPFL.
VERW opcode inside that CLEAR_CPU_BUFFERS modifies ZF flag.
Is that ZF flag damage OK?

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Jari Ruusu  4096R/8132F189 12D6 4C3A DCDA 0AA4 27BD  ACDF F073 3C80 8132 F189