From: Penny Zheng <Penny.Zheng@arm.com>
To: Julien Grall <julien@xen.org>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
"sstabellini@kernel.org" <sstabellini@kernel.org>
Cc: Andre Przywara <Andre.Przywara@arm.com>,
Bertrand Marquis <Bertrand.Marquis@arm.com>,
Wei Chen <Wei.Chen@arm.com>, Kaly Xin <Kaly.Xin@arm.com>,
nd <nd@arm.com>
Subject: RE: [PATCH] xen/arm: Add Cortex-A73 erratum 858921 workaround
Date: Tue, 10 Nov 2020 09:31:37 +0000 [thread overview]
Message-ID: <VE1PR08MB521542C55E70B3280B51175DF7E90@VE1PR08MB5215.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <cfa63398-8182-b79f-1602-ed068e2319ad@xen.org>
> -----Original Message-----
> From: Julien Grall <julien@xen.org>
> Sent: Monday, November 9, 2020 8:04 PM
> To: Penny Zheng <Penny.Zheng@arm.com>; xen-devel@lists.xenproject.org;
> sstabellini@kernel.org
> Cc: Andre Przywara <Andre.Przywara@arm.com>; Bertrand Marquis
> <Bertrand.Marquis@arm.com>; Wei Chen <Wei.Chen@arm.com>; Kaly Xin
> <Kaly.Xin@arm.com>; nd <nd@arm.com>
> Subject: Re: [PATCH] xen/arm: Add Cortex-A73 erratum 858921 workaround
>
> Hi,
>
> On 09/11/2020 08:21, Penny Zheng wrote:
> > CNTVCT_EL0 or CNTPCT_EL0 counter read in Cortex-A73 (all versions)
> > might return a wrong value when the counter crosses a 32bit boundary.
> >
> > Until now, there is no case for Xen itself to access CNTVCT_EL0, and
> > it also should be the Guest OS's responsibility to deal with this
> > part.
> >
> > But for CNTPCT, there exists several cases in Xen involving reading
> > CNTPCT, so a possible workaround is that performing the read twice,
> > and to return one or the other depending on whether a transition has
> > taken place.
> >
> > Signed-off-by: Penny Zheng <penny.zheng@arm.com>
>
> Acked-by: Julien Grall <jgrall@amazon.com>
>
Thank you. 😉
> On a related topic, do we need a fix similar to Linux commit 75a19a0202db
> "arm64: arch_timer: Ensure counter register reads occur with seqlock held"?
>
Sure, I'll check this commit and talk with my teams for further work.
Cheers
--
Penny Zheng
> Cheers,
>
> --
> Julien Grall
next prev parent reply other threads:[~2020-11-10 9:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-09 8:21 [PATCH] xen/arm: Add Cortex-A73 erratum 858921 workaround Penny Zheng
2020-11-09 9:01 ` Wei Chen
2020-11-09 10:31 ` Bertrand Marquis
2020-11-09 12:04 ` Julien Grall
2020-11-10 9:31 ` Penny Zheng [this message]
2020-11-13 3:37 ` Wei Chen
2020-11-26 0:00 ` Stefano Stabellini
2020-11-26 2:07 ` Wei Chen
2020-11-26 10:55 ` Julien Grall
2020-11-26 11:27 ` Wei Chen
2020-12-02 18:11 ` Julien Grall
2020-12-03 3:34 ` Wei Chen
2020-12-03 4:15 ` Stefano Stabellini
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