From: David Miller <davem@davemloft.net>
To: jasowang@redhat.com
Cc: mst@redhat.com, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
hch@infradead.org, James.Bottomley@HansenPartnership.com,
aarcange@redhat.com, tglx@linutronix.de, mingo@redhat.com,
peterz@infradead.org, dvhart@infradead.org
Subject: Re: [PATCH net] vhost: don't use kmap() to log dirty pages
Date: Mon, 13 May 2019 09:42:18 -0700 (PDT) [thread overview]
Message-ID: <20190513.094218.1962516460150696760.davem@davemloft.net> (raw)
In-Reply-To: <1557725265-63525-1-git-send-email-jasowang@redhat.com>
From: Jason Wang <jasowang@redhat.com>
Date: Mon, 13 May 2019 01:27:45 -0400
> Vhost log dirty pages directly to a userspace bitmap through GUP and
> kmap_atomic() since kernel doesn't have a set_bit_to_user()
> helper. This will cause issues for the arch that has virtually tagged
> caches. The way to fix is to keep using userspace virtual
> address. Fortunately, futex has arch_futex_atomic_op_inuser() which
> could be used for setting a bit to user.
>
> Note there're several cases that futex helper can fail e.g a page
> fault or the arch that doesn't have the support. For those cases, a
> simplified get_user()/put_user() pair protected by a global mutex is
> provided as a fallback. The fallback may lead false positive that
> userspace may see more dirty pages.
>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Darren Hart <dvhart@infradead.org>
> Fixes: 3a4d5c94e9593 ("vhost_net: a kernel-level virtio server")
> Signed-off-by: Jason Wang <jasowang@redhat.com>
I want to see a review from Michael for this change before applying.
next prev parent reply other threads:[~2019-05-13 16:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-13 5:27 [PATCH net] vhost: don't use kmap() to log dirty pages Jason Wang
2019-05-13 16:42 ` David Miller
2019-05-13 16:42 ` David Miller [this message]
2019-05-14 3:42 ` Jason Wang
2019-05-14 3:42 ` Jason Wang
2019-05-13 21:55 ` kbuild test robot
2019-05-14 22:16 ` Michael S. Tsirkin
2019-05-14 22:16 ` Michael S. Tsirkin
2019-05-15 2:55 ` Jason Wang
2019-05-15 2:55 ` Jason Wang
2019-05-13 5:27 Jason Wang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190513.094218.1962516460150696760.davem@davemloft.net \
--to=davem@davemloft.net \
--cc=James.Bottomley@HansenPartnership.com \
--cc=aarcange@redhat.com \
--cc=dvhart@infradead.org \
--cc=hch@infradead.org \
--cc=jasowang@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=mst@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=virtualization@lists.linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.