[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requies
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested |
Date: |
Thu, 21 Mar 2013 09:03:57 +0200 |
On Wed, Mar 20, 2013 at 11:55:54PM -0700, Roland Dreier wrote:
> On Wed, Mar 20, 2013 at 11:18 PM, Michael S. Tsirkin <address@hidden> wrote:
> > core/umem.c seems to get the arguments to get_user_pages
> > in the reverse order: it sets writeable flag and
> > breaks COW for MAP_SHARED if and only if hardware needs to
> > write the page.
> >
> > This breaks memory overcommit for users such as KVM:
> > each time we try to register a page to send it to remote, this
> > breaks COW. It seems that for applications that only have
> > REMOTE_READ permission, there is no reason to break COW at all.
>
> I proposed a similar (but not exactly the same, see below) patch a
> while ago: https://lkml.org/lkml/2012/1/26/7 but read the thread,
> especially https://lkml.org/lkml/2012/2/6/265
>
> I think this change will break the case where userspace tries to
> register an MR with read-only permission, but intends locally through
> the CPU to write to the memory.
Shouldn't it set LOCAL_WRITE then?
- [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Michael S. Tsirkin, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Michael R. Hines, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Roland Dreier, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Roland Dreier, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Michael S. Tsirkin, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Roland Dreier, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Michael S. Tsirkin, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Jason Gunthorpe, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Michael S. Tsirkin, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Jason Gunthorpe, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Michael S. Tsirkin, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Jason Gunthorpe, 2013/03/21
- Re: [Qemu-devel] [PATCH] rdma: don't make pages writeable if not requiested, Michael S. Tsirkin, 2013/03/21