linux-kernel - Re: [PATCH v3] x86-64/Xen: fix stack switching

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Date:   Wed, 16 Jan 2019 12:51:20 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Jan Beulich <JBeulich@...e.com>, Ingo Molnar <mingo@...e.hu>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Andrew Lutomirski <luto@...nel.org>,
        xen-devel <xen-devel@...ts.xenproject.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] x86-64/Xen: fix stack switching

On 15/01/2019 17:58, Jan Beulich wrote:
> While in the native case entry into the kernel happens on the trampoline
> stack, PV Xen kernels get entered with the current thread stack right
> away. Hence source and destination stacks are identical in that case,
> and special care is needed.
> 
> Other than in sync_regs() the copying done on the INT80 path isn't
> NMI / #MC safe, as either of these events occurring in the middle of the
> stack copying would clobber data on the (source) stack.
> 
> I'm not altering the similar code in interrupt_entry() and nmi(), as
> those code paths are unreachable afaict when running PV Xen guests.
> 
> Fixes: 7f2590a110b837af5679d08fc25c6227c5a8c497
> Signed-off-by: Jan Beulich <jbeulich@...e.com>
> Cc: stable@...nel.org 

Reviewed-by: Juergen Gross <jgross@...e.com>


Juergen