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From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Singh, Balbir" <sblbir@amazon.com>,
	"Valentin, Eduardo" <eduval@amazon.com>,
	"boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Agarwal, Anchal" <anchalag@amazon.com>,
	"Woodhouse, David" <dwmw@amazon.co.uk>,
	"vkuznets@redhat.com" <vkuznets@redhat.com>,
	"sstabellini@kernel.org" <sstabellini@kernel.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"Woodhouse@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com" 
	<Woodhouse@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"jgross@suse.com" <jgross@suse.com>,
	"pavel@ucw.cz" <pavel@ucw.cz>,
	"axboe@kernel.dk" <axboe@kernel.dk>,
	"x86@kernel.org" <x86@kernel.org>,
	"roger.pau@citrix.com" <roger.pau@citrix.com>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"rjw@rjwysocki.net" <rjw@rjwysocki.net>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"Kamata, Munehisa" <kamatam@amazon.com>,
	"bp@alien8.de" <bp@alien8.de>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"konrad.wilk@oracle.co" <konrad.wilk@oracle.co>,
	"len.brown@intel.com" <len.brown@intel.com>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"fllinden@amaozn.com" <fllinden@amaozn.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [RFC PATCH V2 11/11] x86: tsc: avoid system instability in hibernation
Date: Mon, 13 Jan 2020 22:50:59 +0100	[thread overview]
Message-ID: <CAJZ5v0jv+5aLY3N4wFSitu61o9S8tJWEWGGn1Xyw-P82_TwFdQ@mail.gmail.com> (raw)
In-Reply-To: <20200113124247.GG2827@hirez.programming.kicks-ass.net>

On Mon, Jan 13, 2020 at 1:43 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Mon, Jan 13, 2020 at 11:43:18AM +0000, Singh, Balbir wrote:
> > For your original comment, just wanted to clarify the following:
> >
> > 1. After hibernation, the machine can be resumed on a different but compatible
> > host (these are VM images hibernated)
> > 2. This means the clock between host1 and host2 can/will be different
> >
> > In your comments are you making the assumption that the host(s) is/are the
> > same? Just checking the assumptions being made and being on the same page with
> > them.
>
> I would expect this to be the same problem we have as regular suspend,
> after power off the TSC will have been reset, so resume will have to
> somehow bridge that gap. I've no idea if/how it does that.

In general, this is done by timekeeping_resume() and the only special
thing done for the TSC appears to be the tsc_verify_tsc_adjust(true)
call in tsc_resume().

> I remember some BIOSes had crazy TSC ideas for suspend2ram, and we grew
> tsc_restore_sched_clock_state() for it.
>
> Playing crazy games like what you're doing just isn't it though.

Right.

WARNING: multiple messages have this Message-ID (diff)
From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "konrad.wilk@oracle.co" <konrad.wilk@oracle.co>,
	"Valentin, Eduardo" <eduval@amazon.com>,
	"len.brown@intel.com" <len.brown@intel.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"pavel@ucw.cz" <pavel@ucw.cz>, "hpa@zytor.com" <hpa@zytor.com>,
	"boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>,
	"sstabellini@kernel.org" <sstabellini@kernel.org>,
	"fllinden@amaozn.com" <fllinden@amaozn.com>,
	"Kamata, Munehisa" <kamatam@amazon.com>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"Singh, Balbir" <sblbir@amazon.com>,
	"axboe@kernel.dk" <axboe@kernel.dk>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"Agarwal, Anchal" <anchalag@amazon.com>,
	"bp@alien8.de" <bp@alien8.de>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"jgross@suse.com" <jgross@suse.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"Woodhouse@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com"
	<Woodhouse@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com>,
	"rjw@rjwysocki.net" <rjw@rjwysocki.net>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"vkuznets@redhat.com" <vkuznets@redhat.com>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"Woodhouse, David" <dwmw@amazon.co.uk>,
	"roger.pau@citrix.com" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [RFC PATCH V2 11/11] x86: tsc: avoid system instability in hibernation
Date: Mon, 13 Jan 2020 22:50:59 +0100	[thread overview]
Message-ID: <CAJZ5v0jv+5aLY3N4wFSitu61o9S8tJWEWGGn1Xyw-P82_TwFdQ@mail.gmail.com> (raw)
In-Reply-To: <20200113124247.GG2827@hirez.programming.kicks-ass.net>

On Mon, Jan 13, 2020 at 1:43 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Mon, Jan 13, 2020 at 11:43:18AM +0000, Singh, Balbir wrote:
> > For your original comment, just wanted to clarify the following:
> >
> > 1. After hibernation, the machine can be resumed on a different but compatible
> > host (these are VM images hibernated)
> > 2. This means the clock between host1 and host2 can/will be different
> >
> > In your comments are you making the assumption that the host(s) is/are the
> > same? Just checking the assumptions being made and being on the same page with
> > them.
>
> I would expect this to be the same problem we have as regular suspend,
> after power off the TSC will have been reset, so resume will have to
> somehow bridge that gap. I've no idea if/how it does that.

In general, this is done by timekeeping_resume() and the only special
thing done for the TSC appears to be the tsc_verify_tsc_adjust(true)
call in tsc_resume().

> I remember some BIOSes had crazy TSC ideas for suspend2ram, and we grew
> tsc_restore_sched_clock_state() for it.
>
> Playing crazy games like what you're doing just isn't it though.

Right.

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  reply	other threads:[~2020-01-13 21:51 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-07 23:45 [RFC PATCH V2 11/11] x86: tsc: avoid system instability in hibernation Anchal Agarwal
2020-01-07 23:45 ` [Xen-devel] " Anchal Agarwal
2020-01-08 10:50 ` Peter Zijlstra
2020-01-08 10:50   ` [Xen-devel] " Peter Zijlstra
2020-01-10 15:35   ` Eduardo Valentin
2020-01-10 15:35     ` [Xen-devel] " Eduardo Valentin
2020-01-13 10:16     ` Peter Zijlstra
2020-01-13 10:16       ` [Xen-devel] " Peter Zijlstra
2020-01-13 11:43       ` Singh, Balbir
2020-01-13 11:43         ` [Xen-devel] " Singh, Balbir
2020-01-13 11:43         ` Singh, Balbir
2020-01-13 11:48         ` Rafael J. Wysocki
2020-01-13 11:48           ` [Xen-devel] " Rafael J. Wysocki
2020-01-13 11:48           ` Rafael J. Wysocki
2020-01-13 12:42         ` Peter Zijlstra
2020-01-13 12:42           ` [Xen-devel] " Peter Zijlstra
2020-01-13 12:42           ` Peter Zijlstra
2020-01-13 21:50           ` Rafael J. Wysocki [this message]
2020-01-13 21:50             ` [Xen-devel] " Rafael J. Wysocki
2020-01-13 21:50             ` Rafael J. Wysocki
2020-01-13 23:30             ` Rafael J. Wysocki
2020-01-13 23:30               ` [Xen-devel] " Rafael J. Wysocki
2020-01-13 23:30               ` Rafael J. Wysocki
2020-01-14 19:29               ` Anchal Agarwal
2020-01-14 19:29                 ` [Xen-devel] " Anchal Agarwal
2020-01-22 20:07                 ` Anchal Agarwal
2020-01-22 20:07                   ` [Xen-devel] " Anchal Agarwal
2020-01-23 16:27                   ` Boris Ostrovsky
2020-01-23 16:27                     ` [Xen-devel] " Boris Ostrovsky
2020-01-13 13:01         ` Andrew Cooper
2020-01-13 13:01           ` Andrew Cooper
2020-01-13 13:01           ` Andrew Cooper
2020-01-13 13:54           ` David Woodhouse
2020-01-13 13:54             ` David Woodhouse
2020-01-13 13:54             ` David Woodhouse
2020-01-13 15:02           ` Singh, Balbir
2020-01-13 15:02             ` Singh, Balbir
2020-01-13 15:02             ` Singh, Balbir

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