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From: "Jan Beulich" <JBeulich@suse.com>
To: "Boris Ostrovsky" <boris.ostrovsky@oracle.com>
Cc: "Roger Pau Monne" <roger.pau@citrix.com>,
	"xen-devel" <xen-devel@lists.xenproject.org>,
	"Juergen Gross" <jgross@suse.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [Xen-devel] [PATCH 4/4] xen/PVH: Remove reserved entry in PVH GDT
Date: Wed, 02 May 2018 09:07:24 -0600	[thread overview]
Message-ID: <5AE9D42C02000078001C030D@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <ee05bb34-7671-3069-3eb0-f794a2dc68a4@oracle.com>

>>> On 02.05.18 at 17:06, <boris.ostrovsky@oracle.com> wrote:
> On 05/02/2018 04:26 AM, Jan Beulich wrote:
>>>>> On 01.05.18 at 14:34, <boris.ostrovsky@oracle.com> wrote:
>>> On 05/01/2018 04:00 AM, Roger Pau Monné wrote:
>>>> On Mon, Apr 30, 2018 at 12:23:39PM -0400, Boris Ostrovsky wrote:
>>>>> And without it we can't use _BOOT_XX macros any longer so define new ones.
>>>> Not being that familiar with Linux internals I'm not sure I see the
>>>> benefit of this. Isn't there a risk that some other code is going to
>>>> use the __BOOT_XX defines?
>>> The startup code we are jumping to loads their own GDT and I don't see 
>>> any explicit references to segments.
>> No explicit references to segments isn't enough: You also need to make
>> sure no exceptions at all can occur while loaded selectors and GDT are
>> out of sync - in particular NMI might be of concern here (this isn't PV
>> after all, where not having a callback registered effectively masks NMI).
> 
> How would keeping __BOOT_XX selectors help with NMI? We don't have
> anything set up for NMI handling anyway yet, this is all done in x86
> startup code later.

Oh, you're right - there's no IDT either, so an NMI would yield a triple fault
anyway.

Jan

  reply	other threads:[~2018-05-02 15:07 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-30 16:23 [PATCH 0/4] PVH GDT fixes and cleanup Boris Ostrovsky
2018-04-30 16:23 ` [PATCH 1/4] xen/PVH: Replace GDT_ENTRY with explicit constant Boris Ostrovsky
2018-04-30 16:57   ` [Xen-devel] " Roger Pau Monné
2018-04-30 18:07     ` Boris Ostrovsky
2018-05-01  7:53       ` Roger Pau Monné
2018-05-01 12:16         ` Boris Ostrovsky
2018-05-01 11:31   ` David Laight
2018-05-01 12:40     ` Boris Ostrovsky
2018-05-02  8:00   ` [Xen-devel] " Jan Beulich
2018-05-02 14:53     ` Boris Ostrovsky
2018-04-30 16:23 ` [PATCH 2/4] xen/PVH: Use proper CS selector in long mode Boris Ostrovsky
2018-05-02  8:05   ` [Xen-devel] " Jan Beulich
2018-05-02 14:57     ` Boris Ostrovsky
2018-05-02 15:00       ` Jan Beulich
2018-05-02 15:08         ` Boris Ostrovsky
2018-05-02 15:09           ` Jan Beulich
2018-05-02 15:28             ` Andrew Cooper
2018-04-30 16:23 ` [PATCH 3/4] xen/PVH: Set up GS segment for stack canary Boris Ostrovsky
2018-05-02  8:16   ` [Xen-devel] " Jan Beulich
2018-05-02 15:00     ` Boris Ostrovsky
2018-05-02 15:01       ` Jan Beulich
2018-05-02 15:22         ` Boris Ostrovsky
2018-05-02 15:41           ` Jan Beulich
2018-05-02 17:29             ` Boris Ostrovsky
2018-05-03  7:35               ` Jan Beulich
2018-04-30 16:23 ` [PATCH 4/4] xen/PVH: Remove reserved entry in PVH GDT Boris Ostrovsky
2018-05-01  8:00   ` [Xen-devel] " Roger Pau Monné
2018-05-01 12:34     ` Boris Ostrovsky
2018-05-02  8:26       ` Jan Beulich
2018-05-02 15:06         ` Boris Ostrovsky
2018-05-02 15:07           ` Jan Beulich [this message]
2018-05-02  8:19   ` Jan Beulich

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