From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jerome Glisse <jglisse@redhat.com>
Cc: aarcange@redhat.com, kvm@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, linux-mm@kvack.org
Subject: Re: [RFC PATCH V2 5/5] vhost: access vq metadata through kernel virtual address
Date: Thu, 7 Mar 2019 21:21:03 -0500 [thread overview]
Message-ID: <20190307211506-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20190307191720.GF3835@redhat.com>
On Thu, Mar 07, 2019 at 02:17:20PM -0500, Jerome Glisse wrote:
> > It's because of all these issues that I preferred just accessing
> > userspace memory and handling faults. Unfortunately there does not
> > appear to exist an API that whitelists a specific driver along the lines
> > of "I checked this code for speculative info leaks, don't add barriers
> > on data path please".
>
> Maybe it would be better to explore adding such helper then remapping
> page into kernel address space ?
I explored it a bit (see e.g. thread around: "__get_user slower than
get_user") and I can tell you it's not trivial given the issue is around
security. So in practice it does not seem fair to keep a significant
optimization out of kernel because *maybe* we can do it differently even
better :)
--
MST
WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jerome Glisse <jglisse@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>,
kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
peterx@redhat.com, linux-mm@kvack.org, aarcange@redhat.com
Subject: Re: [RFC PATCH V2 5/5] vhost: access vq metadata through kernel virtual address
Date: Thu, 7 Mar 2019 21:21:03 -0500 [thread overview]
Message-ID: <20190307211506-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20190307191720.GF3835@redhat.com>
On Thu, Mar 07, 2019 at 02:17:20PM -0500, Jerome Glisse wrote:
> > It's because of all these issues that I preferred just accessing
> > userspace memory and handling faults. Unfortunately there does not
> > appear to exist an API that whitelists a specific driver along the lines
> > of "I checked this code for speculative info leaks, don't add barriers
> > on data path please".
>
> Maybe it would be better to explore adding such helper then remapping
> page into kernel address space ?
I explored it a bit (see e.g. thread around: "__get_user slower than
get_user") and I can tell you it's not trivial given the issue is around
security. So in practice it does not seem fair to keep a significant
optimization out of kernel because *maybe* we can do it differently even
better :)
--
MST
next prev parent reply other threads:[~2019-03-08 2:21 UTC|newest]
Thread overview: 175+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-06 7:18 [RFC PATCH V2 0/5] vhost: accelerate metadata access through vmap() Jason Wang
2019-03-06 7:18 ` Jason Wang
2019-03-06 7:18 ` [RFC PATCH V2 1/5] vhost: generalize adding used elem Jason Wang
2019-03-06 7:18 ` Jason Wang
2019-03-06 7:18 ` [RFC PATCH V2 2/5] vhost: fine grain userspace memory accessors Jason Wang
2019-03-06 10:45 ` Christophe de Dinechin
2019-03-06 10:45 ` Christophe de Dinechin
2019-03-07 2:38 ` Jason Wang
2019-03-07 2:38 ` Jason Wang
2019-03-06 7:18 ` Jason Wang
2019-03-06 7:18 ` [RFC PATCH V2 3/5] vhost: rename vq_iotlb_prefetch() to vq_meta_prefetch() Jason Wang
2019-03-06 7:18 ` Jason Wang
2019-03-06 7:18 ` [RFC PATCH V2 4/5] vhost: introduce helpers to get the size of metadata area Jason Wang
2019-03-06 7:18 ` Jason Wang
2019-03-06 10:56 ` Christophe de Dinechin
2019-03-07 2:40 ` Jason Wang
2019-03-07 2:40 ` Jason Wang
2019-03-06 10:56 ` Christophe de Dinechin
2019-03-06 18:43 ` Souptick Joarder
2019-03-07 2:42 ` Jason Wang
2019-03-07 2:42 ` Jason Wang
2019-03-06 7:18 ` [RFC PATCH V2 5/5] vhost: access vq metadata through kernel virtual address Jason Wang
2019-03-06 16:31 ` Michael S. Tsirkin
2019-03-06 16:31 ` Michael S. Tsirkin
2019-03-07 2:45 ` Jason Wang
2019-03-07 2:45 ` Jason Wang
2019-03-07 15:34 ` Michael S. Tsirkin
2019-03-07 15:34 ` Michael S. Tsirkin
2019-03-07 19:09 ` Jerome Glisse
2019-03-07 19:09 ` Jerome Glisse
2019-03-07 19:38 ` Andrea Arcangeli
2019-03-07 19:38 ` Andrea Arcangeli
2019-03-07 20:17 ` Jerome Glisse
2019-03-07 20:17 ` Jerome Glisse
2019-03-07 21:27 ` Andrea Arcangeli
2019-03-07 21:27 ` Andrea Arcangeli
2019-03-08 9:13 ` Jason Wang
2019-03-08 9:13 ` Jason Wang
2019-03-08 19:11 ` Andrea Arcangeli
2019-03-11 7:21 ` Jason Wang
2019-03-11 7:21 ` Jason Wang
2019-03-08 19:11 ` Andrea Arcangeli
2019-03-11 14:45 ` Jan Kara
2019-03-11 14:45 ` Jan Kara
2019-03-08 8:31 ` Jason Wang
2019-03-08 8:31 ` Jason Wang
2019-03-07 15:47 ` Michael S. Tsirkin
2019-03-07 17:56 ` Michael S. Tsirkin
2019-03-07 17:56 ` Michael S. Tsirkin
2019-03-07 19:16 ` Andrea Arcangeli
2019-03-07 19:16 ` Andrea Arcangeli
2019-03-08 8:50 ` Jason Wang
2019-03-08 8:50 ` Jason Wang
2019-03-08 14:58 ` Jerome Glisse
2019-03-11 7:18 ` Jason Wang
2019-03-11 7:18 ` Jason Wang
2019-03-08 14:58 ` Jerome Glisse
2019-03-08 19:48 ` Andrea Arcangeli
2019-03-08 19:48 ` Andrea Arcangeli
2019-03-08 20:06 ` Jerome Glisse
2019-03-08 20:06 ` Jerome Glisse
2019-03-11 7:40 ` Jason Wang
2019-03-11 7:40 ` Jason Wang
2019-03-11 12:48 ` Michael S. Tsirkin
2019-03-11 13:43 ` Andrea Arcangeli
2019-03-11 13:43 ` Andrea Arcangeli
2019-03-12 2:56 ` Jason Wang
2019-03-12 3:51 ` Michael S. Tsirkin
2019-03-12 3:51 ` Michael S. Tsirkin
2019-03-12 2:56 ` Jason Wang
2019-03-12 2:52 ` Jason Wang
2019-03-12 2:52 ` Jason Wang
2019-03-12 3:50 ` Michael S. Tsirkin
2019-03-12 3:50 ` Michael S. Tsirkin
2019-03-12 7:15 ` Jason Wang
2019-03-12 7:15 ` Jason Wang
2019-03-11 12:48 ` Michael S. Tsirkin
2019-03-07 19:17 ` Jerome Glisse
2019-03-08 2:21 ` Michael S. Tsirkin [this message]
2019-03-08 2:21 ` Michael S. Tsirkin
2019-03-08 2:55 ` Jerome Glisse
2019-03-08 2:55 ` Jerome Glisse
2019-03-08 3:16 ` Michael S. Tsirkin
2019-03-08 3:16 ` Michael S. Tsirkin
2019-03-08 3:40 ` Jerome Glisse
2019-03-08 3:43 ` Michael S. Tsirkin
2019-03-08 3:45 ` Jerome Glisse
2019-03-08 9:15 ` Jason Wang
2019-03-08 9:15 ` Jason Wang
2019-03-08 3:45 ` Jerome Glisse
2019-03-08 3:43 ` Michael S. Tsirkin
2019-03-08 3:40 ` Jerome Glisse
2019-03-08 8:58 ` Jason Wang
2019-03-08 8:58 ` Jason Wang
2019-03-08 12:56 ` Michael S. Tsirkin
2019-03-08 15:02 ` Jerome Glisse
2019-03-08 15:02 ` Jerome Glisse
2019-03-08 12:56 ` Michael S. Tsirkin
2019-03-08 19:13 ` Andrea Arcangeli
2019-03-08 19:13 ` Andrea Arcangeli
2019-03-07 19:17 ` Jerome Glisse
2019-03-07 15:47 ` Michael S. Tsirkin
2019-03-06 7:18 ` Jason Wang
2019-03-08 14:12 ` [RFC PATCH V2 0/5] vhost: accelerate metadata access through vmap() Christoph Hellwig
2019-03-08 14:12 ` Christoph Hellwig
2019-03-11 7:13 ` Jason Wang
2019-03-11 7:13 ` Jason Wang
2019-03-11 13:59 ` Michael S. Tsirkin
2019-03-11 13:59 ` Michael S. Tsirkin
2019-03-11 13:59 ` Michael S. Tsirkin
2019-03-11 18:14 ` David Miller
2019-03-11 18:14 ` David Miller
2019-03-12 2:59 ` Jason Wang
2019-03-12 2:59 ` Jason Wang
2019-03-12 3:52 ` Michael S. Tsirkin
2019-03-12 3:52 ` Michael S. Tsirkin
2019-03-12 3:52 ` Michael S. Tsirkin
2019-03-12 7:17 ` Jason Wang
2019-03-12 7:17 ` Jason Wang
2019-03-12 7:17 ` Jason Wang
2019-03-12 11:54 ` Michael S. Tsirkin
2019-03-12 11:54 ` Michael S. Tsirkin
2019-03-12 15:46 ` James Bottomley
2019-03-12 15:46 ` James Bottomley
2019-03-12 20:04 ` Andrea Arcangeli
2019-03-12 20:04 ` Andrea Arcangeli
2019-03-12 20:04 ` Andrea Arcangeli
2019-03-12 20:53 ` James Bottomley
2019-03-12 20:53 ` James Bottomley
2019-03-12 21:11 ` Andrea Arcangeli
2019-03-12 21:11 ` Andrea Arcangeli
2019-03-12 21:19 ` James Bottomley
2019-03-12 21:19 ` James Bottomley
2019-03-12 21:53 ` Andrea Arcangeli
2019-03-12 21:53 ` Andrea Arcangeli
2019-03-12 21:53 ` Andrea Arcangeli
2019-03-12 22:02 ` James Bottomley
2019-03-12 22:02 ` James Bottomley
2019-03-12 22:50 ` Andrea Arcangeli
2019-03-12 22:50 ` Andrea Arcangeli
2019-03-12 22:57 ` James Bottomley
2019-03-12 22:57 ` James Bottomley
2019-03-12 22:50 ` Andrea Arcangeli
2019-03-12 21:11 ` Andrea Arcangeli
2019-03-13 16:05 ` Christoph Hellwig
2019-03-13 16:05 ` Christoph Hellwig
2019-03-13 16:05 ` Christoph Hellwig
2019-03-13 16:05 ` Christoph Hellwig
2019-03-13 16:37 ` James Bottomley
2019-03-13 16:37 ` James Bottomley
2019-03-14 10:42 ` Michael S. Tsirkin
2019-03-14 10:42 ` Michael S. Tsirkin
2019-03-14 13:49 ` Jason Wang
2019-03-14 13:49 ` Jason Wang
2019-03-14 13:49 ` Jason Wang
2019-03-14 19:33 ` Andrea Arcangeli
2019-03-14 19:33 ` Andrea Arcangeli
2019-03-15 4:39 ` Jason Wang
2019-03-15 4:39 ` Jason Wang
2019-03-15 4:39 ` Jason Wang
2019-03-14 19:33 ` Andrea Arcangeli
2019-03-14 10:42 ` Michael S. Tsirkin
2019-03-12 11:54 ` Michael S. Tsirkin
2019-03-12 5:14 ` James Bottomley
2019-03-12 5:14 ` James Bottomley
2019-03-12 7:51 ` Jason Wang
2019-03-12 7:51 ` Jason Wang
2019-03-12 7:51 ` Jason Wang
2019-03-12 7:53 ` Jason Wang
2019-03-12 7:53 ` Jason Wang
2019-03-12 7:53 ` Jason Wang
2019-03-12 2:59 ` Jason Wang
2019-03-11 18:14 ` David Miller
2019-03-11 7:13 ` Jason Wang
2019-03-08 14:12 ` Christoph Hellwig
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