From: David Miller <davem@davemloft.net>
To: mashirle@us.ibm.com
Cc: avi@redhat.com, arnd@arndb.de, mst@redhat.com,
xiaohui.xin@intel.com, netdev@vger.kernel.org,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 2/2] macvtap: TX zero copy between guest and host kernel
Date: Mon, 13 Sep 2010 20:17:30 -0700 (PDT) [thread overview]
Message-ID: <20100913.201730.27805132.davem@davemloft.net> (raw)
In-Reply-To: <1284410883.13351.14.camel@localhost.localdomain>
From: Shirley Ma <mashirle@us.ibm.com>
Date: Mon, 13 Sep 2010 13:48:03 -0700
> + base = (unsigned long)from->iov_base + offset1;
> + size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
> + num_pages = get_user_pages_fast(base, size, 0, &page[i]);
> + if ((num_pages != size) ||
> + (num_pages > MAX_SKB_FRAGS - skb_shinfo(skb)->nr_frags))
> + /* put_page is in skb free */
> + return -EFAULT;
What keeps the user from writing to these pages in it's address space
after the write call returns?
A write() return of success means:
"I wrote what you gave to me"
not
"I wrote what you gave to me, oh and BTW don't touch these
pages for a while."
In fact "a while" isn't even defined in any way, as there is no way
for the write() invoker to know when the networking card is done with
those pages.
next prev parent reply other threads:[~2010-09-14 3:17 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-13 20:43 [RFC PATCH 0/1] macvtap TX zero copy between guest and host kernel Shirley Ma
2010-09-13 20:47 ` RFC PATCH 1/2] macvtap: A new sock zero copy flag Shirley Ma
2010-09-13 20:48 ` [RFC PATCH 2/2] macvtap: TX zero copy between guest and host kernel Shirley Ma
2010-09-14 3:17 ` David Miller [this message]
2010-09-14 9:12 ` Avi Kivity
2010-09-14 15:05 ` Shirley Ma
2010-09-14 15:21 ` Arnd Bergmann
2010-09-14 15:22 ` Michael S. Tsirkin
2010-09-14 16:00 ` Shirley Ma
2010-09-14 16:29 ` Michael S. Tsirkin
2010-09-14 17:02 ` Shirley Ma
2010-09-14 18:27 ` Michael S. Tsirkin
2010-09-14 18:49 ` Shirley Ma
2010-09-14 19:01 ` Michael S. Tsirkin
2010-09-14 19:20 ` Shirley Ma
2010-09-15 5:31 ` Michael S. Tsirkin
2010-09-14 19:36 ` Shirley Ma
2010-09-15 5:12 ` Michael S. Tsirkin
2010-09-15 6:21 ` Shirley Ma
2010-09-15 10:10 ` Michael S. Tsirkin
2010-09-15 14:52 ` Shirley Ma
2010-09-15 15:04 ` Michael S. Tsirkin
2010-09-15 15:39 ` Michael S. Tsirkin
2010-09-15 17:00 ` Shirley Ma
2010-09-15 17:30 ` Michael S. Tsirkin
2010-09-15 18:48 ` Shirley Ma
2010-09-29 3:24 ` Shirley Ma
2010-09-29 8:16 ` Michael S. Tsirkin
2010-09-29 8:28 ` Michael S. Tsirkin
2010-09-29 14:33 ` Shirley Ma
2010-09-29 14:56 ` Shirley Ma
2010-09-29 14:31 ` Shirley Ma
2010-09-29 14:37 ` Shirley Ma
2010-09-29 15:14 ` Michael S. Tsirkin
2010-09-29 15:23 ` Shirley Ma
2010-09-15 2:46 ` Xin, Xiaohui
2010-09-15 9:58 ` Michael S. Tsirkin
2010-09-16 8:18 ` Xin, Xiaohui
2010-09-16 10:02 ` Michael S. Tsirkin
2010-09-15 1:56 ` Xin, Xiaohui
2010-09-15 1:50 ` Xin, Xiaohui
2010-09-15 2:40 ` Shirley Ma
2010-09-15 2:55 ` Xin, Xiaohui
2010-09-15 5:27 ` Michael S. Tsirkin
2010-09-15 6:17 ` Shirley Ma
2010-09-14 12:05 ` [RFC PATCH 0/1] macvtap " Michael S. Tsirkin
2010-09-14 15:15 ` Shirley Ma
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