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Date: Wed, 17 Jan 2018 10:02:38 +0100
From: Joerg Roedel <joro@8bytes.org>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Andrea Arcangeli <aarcange@redhat.com>,
        Waiman Long <llong@redhat.com>, jroedel@suse.de
Subject: Re: [PATCH 02/16] x86/entry/32: Enter the kernel via trampoline stack
Message-ID: <20180117090238.GH28161@8bytes.org>
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Hi Boris,

thanks for testing this :)

On Tue, Jan 16, 2018 at 09:47:06PM -0500, Boris Ostrovsky wrote:
> On 01/16/2018 11:36 AM, Joerg Roedel wrote:
> >+.macro SWITCH_TO_KERNEL_STACK nr_regs=0 check_user=0
> 
> 
> This (and next patch's SWITCH_TO_ENTRY_STACK) need X86_FEATURE_PTI check.
> 
> With those macros fixed I was able to boot 32-bit Xen PV guest.

Hmm, on bare metal the stack switch happens regardless of the
X86_FEATURE_PTI feature being set, because we always program tss.sp0
with the systenter stack. How is the kernel entry stack setup on xen-pv?
I think something is missing there instead.

Regards,

	Joerg