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Re: [Qemu-devel] [PATCH v1 1/2] vhost-user: support SET_MEM_TABLE waite
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v1 1/2] vhost-user: support SET_MEM_TABLE waite the result of mmap |
Date: |
Tue, 10 Feb 2015 13:04:22 +0100 |
On Tue, Feb 10, 2015 at 07:59:16PM +0800, Linhaifeng wrote:
>
>
> On 2015/2/10 18:41, Michael S. Tsirkin wrote:
> > On Tue, Feb 10, 2015 at 06:27:04PM +0800, Linhaifeng wrote:
> >>
> >>
> >> On 2015/2/10 16:46, Michael S. Tsirkin wrote:
> >>> On Tue, Feb 10, 2015 at 01:48:12PM +0800, linhaifeng wrote:
> >>>> From: Linhaifeng <address@hidden>
> >>>>
> >>>> Slave should reply to master and set u64 to 0 if
> >>>> mmap all regions success otherwise set u64 to 1.
> >>>>
> >>>> Signed-off-by: Linhaifeng <address@hidden>
> >>>
> >>> How does this work with existig slaves though?
> >>>
> >>
> >> Slaves should work like this:
> >>
> >> int set_mem_table(...)
> >> {
> >> ....
> >> for (idx = 0, i = 0; idx < memory.nregions; idx++) {
> >> ....
> >> mem = mmap(..);
> >> if (MAP_FAILED == mem) {
> >> msg->msg.u64 = 1;
> >> msg->msg.size = MEMB_SIZE(VhostUserMsg, u64);
> >> return 1;
> >> }
> >> }
> >>
> >> ....
> >>
> >> msg->msg.u64 = 0;
> >> msg->msg.size = MEMB_SIZE(VhostUserMsg, u64);
> >> return 1;
> >> }
> >>
> >> If slaves not reply QEMU will always wait.
> >
> > Are you sure existing slaves reply?
>
> No.May be the existing slaves need add reply in their codes.
So that's not good. We need a way to negotiate the capability,
we can't just deadlock with legacy slaves.
> >
> >>>> ---
> >>>> docs/specs/vhost-user.txt | 1 +
> >>>> 1 file changed, 1 insertion(+)
> >>>>
> >>>> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> >>>> index 650bb18..c96bf6b 100644
> >>>> --- a/docs/specs/vhost-user.txt
> >>>> +++ b/docs/specs/vhost-user.txt
> >>>> @@ -171,6 +171,7 @@ Message types
> >>>> Id: 5
> >>>> Equivalent ioctl: VHOST_SET_MEM_TABLE
> >>>> Master payload: memory regions description
> >>>> + Slave payload: u64 (0:success >0:failed)
> >>>>
> >>>> Sets the memory map regions on the slave so it can translate the
> >>>> vring
> >>>> addresses. In the ancillary data there is an array of file
> >>>> descriptors
> >>>> --
> >>>> 1.7.12.4
> >>>>
> >>>
> >>>
> >>
> >> --
> >> Regards,
> >> Haifeng
> >
> > .
> >
>
> --
> Regards,
> Haifeng