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From: "Roger Pau Monné" <roger@xenproject.org>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
	Jan Beulich <jbeulich@suse.com>,
	Teddy Astie <teddy.astie@vates.tech>
Subject: Re: [PATCH] x86/shstk: Fix possible crash while enabling Shadow Stacks
Date: Mon, 19 Oct 2026 20:58:19 +0200	[thread overview]
Message-ID: <atZoSz16waAvDlPw@Mac.lan> (raw)
In-Reply-To: <20261019155959.883789-1-andrew.cooper3@citrix.com>

On Mon, Oct 19, 2026 at 04:59:59PM +0100, Andrew Cooper wrote:
> Between writing MSR_S_CET.SHSTK_EN and establishing SSP using RSTORSSP or
> SETSSBSY, there must not be any CALL or RET instructions.
> 
> Building Xen with -fno-early-inlining causes wrmsr() to become out-of-line,
> and thus suffers #DF during boot.
> 
> Make the MSR and shstk helpers always_inline.  They ought to have been this
> way all along.
> 
> Reported-by: Roger Pau Monné <roger@xenproject.org>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Sorry seems like I'm a bit slow today.  Also worth adding:

Fixes: b60ab42db2f0 ("x86/shstk: Activate Supervisor Shadow Stacks").

Thanks, Roger.


  parent reply	other threads:[~2026-10-19 18:58 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-19 15:59 [PATCH] x86/shstk: Fix possible crash while enabling Shadow Stacks Andrew Cooper
2026-10-19 16:04 ` Teddy Astie
2026-10-19 16:52 ` Roger Pau Monné
2026-10-19 16:53   ` Andrew Cooper
2026-10-19 18:58 ` Roger Pau Monné [this message]
2026-10-20  8:31   ` Andrew Cooper
2026-10-20  8:45     ` Roger Pau Monné

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