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From: Stefano Stabellini <sstabellini@kernel.org>
To: hrg <hrgstephen@gmail.com>
Cc: anthony.perard@citrix.com, xen-devel@lists.xensource.com,
	qemu-devel@nongnu.org, jun.nakajima@intel.com, agraf@suse.de,
	sstabellini@kernel.org, xen-devel@lists.xenproject.org,
	xen-devel@lists.xen.org,
	"Herongguang (Stephen)" <herongguang.he@huawei.com>,
	wangxinxin.wang@huawei.com
Subject: Re: [Qemu-devel] [RFC/BUG] xen-mapcache: buggy invalidate map cache?
Date: Mon, 10 Apr 2017 12:04:15 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.10.1704101159340.2759@sstabellini-ThinkPad-X260> (raw)
In-Reply-To: <CADZi59xEg0SvScgo=Jg0MxTbGYY=nTX18Qo-4GMkfayThDU9zw@mail.gmail.com>

On Mon, 10 Apr 2017, hrg wrote:
> On Sun, Apr 9, 2017 at 11:55 PM, hrg <hrgstephen@gmail.com> wrote:
> > On Sun, Apr 9, 2017 at 11:52 PM, hrg <hrgstephen@gmail.com> wrote:
> >> Hi,
> >>
> >> In xen_map_cache_unlocked(), map to guest memory maybe in entry->next
> >> instead of first level entry (if map to rom other than guest memory
> >> comes first), while in xen_invalidate_map_cache(), when VM ballooned
> >> out memory, qemu did not invalidate cache entries in linked
> >> list(entry->next), so when VM balloon back in memory, gfns probably
> >> mapped to different mfns, thus if guest asks device to DMA to these
> >> GPA, qemu may DMA to stale MFNs.
> >>
> >> So I think in xen_invalidate_map_cache() linked lists should also be
> >> checked and invalidated.
> >>
> >> What’s your opinion? Is this a bug? Is my analyze correct?

Yes, you are right. We need to go through the list for each element of
the array in xen_invalidate_map_cache. Can you come up with a patch?

WARNING: multiple messages have this Message-ID (diff)
From: Stefano Stabellini <sstabellini@kernel.org>
To: hrg <hrgstephen@gmail.com>
Cc: xen-devel@lists.xensource.com, wangxinxin.wang@huawei.com,
	qemu-devel@nongnu.org, agraf@suse.de, sstabellini@kernel.org,
	jun.nakajima@intel.com, anthony.perard@citrix.com,
	xen-devel@lists.xenproject.org, xen-devel@lists.xen.org,
	"Herongguang (Stephen)" <herongguang.he@huawei.com>
Subject: Re: [Qemu-devel] [RFC/BUG] xen-mapcache: buggy invalidate map cache?
Date: Mon, 10 Apr 2017 12:04:15 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.10.1704101159340.2759@sstabellini-ThinkPad-X260> (raw)
In-Reply-To: <CADZi59xEg0SvScgo=Jg0MxTbGYY=nTX18Qo-4GMkfayThDU9zw@mail.gmail.com>

[-- Attachment #1: Type: TEXT/PLAIN, Size: 977 bytes --]

On Mon, 10 Apr 2017, hrg wrote:
> On Sun, Apr 9, 2017 at 11:55 PM, hrg <hrgstephen@gmail.com> wrote:
> > On Sun, Apr 9, 2017 at 11:52 PM, hrg <hrgstephen@gmail.com> wrote:
> >> Hi,
> >>
> >> In xen_map_cache_unlocked(), map to guest memory maybe in entry->next
> >> instead of first level entry (if map to rom other than guest memory
> >> comes first), while in xen_invalidate_map_cache(), when VM ballooned
> >> out memory, qemu did not invalidate cache entries in linked
> >> list(entry->next), so when VM balloon back in memory, gfns probably
> >> mapped to different mfns, thus if guest asks device to DMA to these
> >> GPA, qemu may DMA to stale MFNs.
> >>
> >> So I think in xen_invalidate_map_cache() linked lists should also be
> >> checked and invalidated.
> >>
> >> What’s your opinion? Is this a bug? Is my analyze correct?

Yes, you are right. We need to go through the list for each element of
the array in xen_invalidate_map_cache. Can you come up with a patch?

[-- Attachment #2: Type: text/plain, Size: 127 bytes --]

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  parent reply	other threads:[~2017-04-10 19:04 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-09 15:52 [Qemu-devel] [RFC/BUG] xen-mapcache: buggy invalidate map cache? hrg
2017-04-09 15:52 ` hrg
2017-04-09 15:55 ` hrg
2017-04-09 15:55   ` hrg
2017-04-09 16:36   ` hrg
2017-04-09 16:36     ` hrg
2017-04-09 17:52     ` [Qemu-devel] [Xen-devel] " Alexey G
2017-04-09 17:52       ` [Qemu-devel] " Alexey G
2017-04-10 19:04     ` Stefano Stabellini [this message]
2017-04-10 19:04       ` Stefano Stabellini
2017-04-10 19:50       ` Stefano Stabellini
2017-04-10 19:50         ` Stefano Stabellini
2017-04-11  4:47         ` hrg
2017-04-11  4:47           ` hrg
2017-04-11 22:32           ` Stefano Stabellini
2017-04-11 22:32             ` Stefano Stabellini
2017-04-12  6:17             ` [Qemu-devel] [Xen-devel] " Alexey G
2017-04-12  6:17               ` [Qemu-devel] " Alexey G
2017-04-12  8:28               ` [Qemu-devel] [Xen-devel] " Herongguang (Stephen)
2017-04-12  8:28                 ` [Qemu-devel] " Herongguang (Stephen)
2017-04-12 23:51               ` [Qemu-devel] [Xen-devel] " Stefano Stabellini
2017-04-12 23:51                 ` [Qemu-devel] " Stefano Stabellini
2017-04-12  8:14             ` Herongguang (Stephen)
2017-04-12  8:14               ` Herongguang (Stephen)
2017-04-12 23:51               ` Stefano Stabellini
2017-04-12 23:51                 ` Stefano Stabellini
2017-04-13  5:47                 ` Herongguang (Stephen)
2017-04-13  5:47                   ` Herongguang (Stephen)
2017-04-28 23:51                   ` Stefano Stabellini
2017-04-28 23:51                     ` Stefano Stabellini

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