On Tue, Jan 24, 2017 at 02:42:27PM -0500, David Miller wrote:> From: "Michael S. Tsirkin" <mst at redhat.com> > Date: Mon, 23 Jan 2017 21:37:52 +0200 > > > I don't have any guests with PAGE_SIZE > 64k but the > > code seems to be clearly broken in that case > > as PAGE_SIZE / MERGEABLE_BUFFER_ALIGN will need > > more than 8 bit and so the code in mergeable_ctx_to_buf_address > > does not give us the actual true size. > > > > Cc: John Fastabend <john.fastabend at gmail.com> > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > > Applied, thanks Michael. > > I am really trying to be patient, but we are about to run out of > time for fixing the adjust header XDP stuff. > > That should have been resolved in a week or two, but now we're > basically a month or so later. > > Please come to some kind of agreement about how to implement this > because we can't let v4.10 go out without this being resolved. > > Thank you.I didn't realise. Why can't we? I thought that adjust_header is an optional feature that userspace can test for, so no rush. -- MST
From: "Michael S. Tsirkin" <mst at redhat.com> Date: Tue, 24 Jan 2017 21:53:13 +0200> I didn't realise. Why can't we? I thought that adjust_header is an > optional feature that userspace can test for, so no rush.No, we want the base set of XDP features to be present in all drivers supporting XDP.
On Tue, Jan 24, 2017 at 03:09:59PM -0500, David Miller wrote:> From: "Michael S. Tsirkin" <mst at redhat.com> > Date: Tue, 24 Jan 2017 21:53:13 +0200 > > > I didn't realise. Why can't we? I thought that adjust_header is an > > optional feature that userspace can test for, so no rush. > > No, we want the base set of XDP features to be present in all drivers > supporting XDP.I see, I didn't realize this. In light of this, is there any guidance *how much* head room is required to be considered valid? We already have 12 bytes of headroom. I'm generally sorry it's taking long, a large part of that is difficulty figuring out the requirements: when we discussed this on LPC my take-away was that one of the first users will be fighting DDOS attacks. In light of this, I assumed that - supporting just DROP (or DROP+TX) would already be useful - XDP_PASS shouldn't be too slow as some people will run all their traffic with XDP enabled - people actually want this in virtio because they run in a vm Since then I heard opinions that seem to imply that - you must support all features, not just DROP, otherwise it's useless - XDP_PASS is a slow path fallback as people are not expected to mix XDP with regular sockets - DDOS protection and by extension XDP in virtio is a developer's toy anyway Thus, expect some slowness while I figure it all out. -- MST