linux-kernel - Re: [Xen-devel] [PATCH v2] x86/xen: fix pv boot

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Message-ID: <d8a07a83-2595-f22e-ca9c-313f74bb11ba@citrix.com>
Date:   Wed, 7 Nov 2018 17:36:10 +0000
From:   Andrew Cooper <andrew.cooper3@...rix.com>
To:     Juergen Gross <jgross@...e.com>, <linux-kernel@...r.kernel.org>,
        <xen-devel@...ts.xenproject.org>, <x86@...nel.org>
CC:     <sstabellini@...nel.org>, <mingo@...hat.com>, <bp@...en8.de>,
        <hpa@...or.com>, <boris.ostrovsky@...cle.com>, <tglx@...utronix.de>
Subject: Re: [Xen-devel] [PATCH v2] x86/xen: fix pv boot

On 07/11/18 17:01, Juergen Gross wrote:
> Commit 9da3f2b7405440 ("x86/fault: BUG() when uaccess helpers fault on
> kernel addresses") introduced a regression for booting Xen PV guests.
>
> Xen PV guests are using __put_user() and __get_user() for accessing the
> p2m map (physical to machine frame number map) as accesses might fail
> in case of not populated areas of the map.
>
> With above commit using __put_user() and __get_user() for accessing
> kernel pages is no longer valid. So replace the Xen hack by adding
> appropriate p2m access functions using the default fixup handler.
>
> Fixes: 9da3f2b7405440 ("x86/fault: BUG() when uaccess helpers fault on kernel addresses")
> Signed-off-by: Juergen Gross <jgross@...e.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@...rix.com>