linux-kernel - Re: [PATCHv9 13/16] x86/traps: Handle LASS thrown #SS

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Message-ID: <f2d4b46d-9a8c-462b-be71-27bd02a0ab49@intel.com>
Date: Thu, 10 Jul 2025 18:23:52 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Andy Lutomirski
	<luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
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	<brijesh.singh@....com>, Michael Roth <michael.roth@....com>, Tony Luck
	<tony.luck@...el.com>, Alexey Kardashevskiy <aik@....com>, Alexander Shishkin
	<alexander.shishkin@...ux.intel.com>
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	<linux-efi@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCHv9 13/16] x86/traps: Handle LASS thrown #SS

On 7/7/2025 1:03 AM, Kirill A. Shutemov wrote:
> LASS throws a #GP for any violations except for stack register accesses,
> in which case it throws a #SS instead. Handle this similarly to how other
> LASS violations are handled.
> 
> In case of FRED, before handling #SS as LASS violation, kernel has to
> check if there's a fixup for the exception. It can address #SS due to
> invalid user context on ERETU. See 5105e7687ad3 ("x86/fred: Fixup
> fault on ERETU by jumping to fred_entrypoint_user") for more details.
> 
> Co-developed-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  arch/x86/kernel/traps.c | 41 +++++++++++++++++++++++++++++++++++------
>  1 file changed, 35 insertions(+), 6 deletions(-)
> 

Reviewed-by: Sohil Mehta <sohil.mehta@...el.com>