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From: Thomas Gleixner <tglx@linutronix.de>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: "Nadav Amit" <nadav.amit@gmail.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	"Haiyang Zhang" <haiyangz@microsoft.com>,
	"Stephen Hemminger" <sthemmin@microsoft.com>,
	"Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"Roman Kagan" <rkagan@virtuozzo.com>
Subject: Re: [PATCH v2 1/4] x86/hyper-v: move synic/stimer control structures definitions to hyperv-tlfs.h
Date: Thu, 29 Nov 2018 20:22:10 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.21.1811292021290.1657@nanos.tec.linutronix.de> (raw)
In-Reply-To: <87bm68i099.fsf@vitty.brq.redhat.com>

[-- Attachment #1: Type: text/plain, Size: 1700 bytes --]

On Thu, 29 Nov 2018, Vitaly Kuznetsov wrote:
> Nadav Amit <nadav.amit@gmail.com> writes:
> 
> >> On Nov 28, 2018, at 5:07 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> >> 
> >> On Wed, 28 Nov 2018, Vitaly Kuznetsov wrote:
> >> 
> >>> Nadav Amit <nadav.amit@gmail.com> writes:
> >>> 
> >>>> On a different note: how come all of the hyper-v structs are not marked
> >>>> with the “packed" attribute?
> >>> 
> >>> "packed" should not be needed with proper padding; I vaguely remember
> >>> someone (from x86@?) arguing _against_ "packed".
> >> 
> >> Packed needs to be used, when describing fixed format data structures in
> >> hardware or other ABIs, so the compiler cannot put alignment holes into
> >> them.
> >> 
> >> Using packed for generic data structures might result in suboptimal layouts
> >> and prevents layout randomization.
> >
> > Right, I forgot about the structs randomization. So at least for it, the
> > attribute should be needed.
> >
> 
> Not sure when randomization.s used but Hyper-V drivers will of course be
> utterly broken with it.
> 
> > To prevent conflicts, I think that this series should also add the
> > attribute in a first patch, which would be tagged for stable.
> 
> As the patchset doesn't add new definitions and as Paolo already queued
> it I'd go with a follow-up patch adding "packed" to all hyperv-tlfs.h
> structures. The question is how to avoid conflicts when Linus will be
> merging this. We can do:
> - Topic branch in kvm
> - Send the patch to x86, make topic branch and reabse kvm
> - Send the patch to kvm
> - ... ?
> 
> Paolo/Thomas, what would be your preference?

As Paolo already has it, just route it through his tree please.

Thanks,

	tglx

  reply	other threads:[~2018-11-29 19:22 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-26 15:47 [PATCH v2 0/4] x86/kvm/hyper-v: Implement Direct Mode for synthetic timers Vitaly Kuznetsov
2018-11-26 15:47 ` [PATCH v2 1/4] x86/hyper-v: move synic/stimer control structures definitions to hyperv-tlfs.h Vitaly Kuznetsov
2018-11-26 17:00   ` Michael Kelley
2018-11-26 20:04   ` Roman Kagan
2018-11-27 13:10     ` Vitaly Kuznetsov
2018-11-27 15:52       ` Michael Kelley
2018-11-27 16:32         ` Vitaly Kuznetsov
2018-11-27 18:48       ` Roman Kagan
2018-11-28  1:49         ` Nadav Amit
2018-11-28 10:37           ` Vitaly Kuznetsov
2018-11-28 13:07             ` Thomas Gleixner
2018-11-28 17:55               ` Nadav Amit
2018-11-29 11:36                 ` Vitaly Kuznetsov
2018-11-29 19:22                   ` Thomas Gleixner [this message]
2018-11-29  7:52               ` Roman Kagan
2018-11-28  8:40         ` Paolo Bonzini
2018-11-26 15:47 ` [PATCH v2 2/4] x86/kvm/hyper-v: use stimer config definition from hyperv-tlfs.h Vitaly Kuznetsov
2018-11-26 15:47 ` [PATCH v2 3/4] x86/kvm/hyper-v: direct mode for synthetic timers Vitaly Kuznetsov
2018-11-26 16:44   ` Paolo Bonzini
2018-11-26 17:14     ` Vitaly Kuznetsov
2018-11-27  8:37     ` Roman Kagan
2018-11-27 13:54       ` Paolo Bonzini
2018-11-27 19:05         ` Roman Kagan
2018-11-28  8:43           ` Paolo Bonzini
2018-11-27  8:21   ` Roman Kagan
2018-12-03 17:12   ` Roman Kagan
2018-12-04 12:36     ` Vitaly Kuznetsov
2018-12-10 12:06   ` Roman Kagan
2018-12-10 12:54     ` Vitaly Kuznetsov
2018-12-10 13:21       ` Roman Kagan
2018-12-10 14:53         ` Vitaly Kuznetsov
2018-11-26 15:47 ` [PATCH v2 4/4] x86/kvm/hyper-v: avoid open-coding stimer_mark_pending() in kvm_hv_notify_acked_sint() Vitaly Kuznetsov
2018-11-26 16:45   ` Paolo Bonzini
2018-11-27  8:49   ` Roman Kagan
2018-11-26 16:45 ` [PATCH v2 0/4] x86/kvm/hyper-v: Implement Direct Mode for synthetic timers Paolo Bonzini

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