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Re: [Qemu-devel] VhostUserRequest # 20
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] VhostUserRequest # 20 |
Date: |
Thu, 1 Jun 2017 18:20:47 +0100 |
User-agent: |
Mutt/1.8.2 (2017-04-18) |
* Marc-André Lureau (address@hidden) wrote:
> Hi
>
> ----- Original Message -----
> > * Marc-André Lureau (address@hidden) wrote:
> > > HI
> > >
> > > ----- Original Message -----
> > > > Hi,
> > > > libvhost-user.h defines:
> > > > VHOST_USER_INPUT_GET_CONFIG = 20,
> > >
> > > That slipped by mistake from my vhost-user-input series WIP, please send a
> > > fix.
> > > (luckily, this is only internal header for now)
> >
> > OK, just posted.
> >
> > However, I just spotted, or should I say gcc just spotted another issue:
> >
> > CC tests/vhost-user-bridge.o
> > /home/dgilbert/git/qemu-world3/tests/vhost-user-bridge.c:228:23: warning:
> > variables 'front' and 'iov' used in loop condition not modified in loop body
> > [-Wfor-loop-analysis]
> > for (cur = front; front != iov; cur++) {
> > ^~~~~ ~~~
> > 1 warning generated.
> >
> >
> > static void
> > iov_restore_front(struct iovec *front, struct iovec *iov, size_t bytes)
> > {
> > struct iovec *cur;
> >
> > for (cur = front; front != iov; cur++) {
> > bytes -= cur->iov_len;
> > }
> >
> > cur->iov_base -= bytes;
> > cur->iov_len += bytes;
> > }
> >
> > What's that actually intending to do?
>
> It was meant to revert the effect of iov_discard_front()
>
> The code should read:
>
> for (cur = front; cur != iov; cur++) {
>
> In practice, it doesn't reach the loop since the front sg buffer is big
> enough to discard the header..
>
> Does that looks correct to you?
OK, so let me check if I understand; it's supposed to be called with
'front' being the original struct iovec *, and 'bytes' being the number
of bytes you shaved off using iov_discard_front?
If so then yes I think that makes sense; a comment to explain that
would probably help.
A sanity check for bytes being >=0 after the loop might be worth it as
well.
Dave
>
>
> thanks
>
> >
> > Dave
> >
> > > thanks
> > >
> > > > while
> > > > vhost-user.c defines:
> > > > VHOST_USER_NET_SET_MTU = 20,
> > > >
> > > > who wins?
> > > >
> > > > Dave
> > > > --
> > > > Dr. David Alan Gilbert / address@hidden / Manchester, UK
> > > >
> > --
> > Dr. David Alan Gilbert / address@hidden / Manchester, UK
> >
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
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