Re: [win-pv-devel] [PATCH] Avoid making hypercalls in the SyncWorker DPC

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Il 21/11/2014 14:24, Paul Durrant ha scritto:
> > -----Original Message-----
> > From: Fabio Fantoni [mailto:fabio.fantoni@xxxxxxx]
> > Sent: 21 November 2014 10:30
> > To: Paul Durrant; win-pv-devel@xxxxxxxxxxxxxxxxxxxx
> > Subject: Re: [win-pv-devel] [PATCH] Avoid making hypercalls in the
> > SyncWorker DPC
> >
> > Il 20/11/2014 17:25, Paul Durrant ha scritto:
> > > The code has to run with interrupts disabled on all CPUs apart from 0 to
> > > corale them across a suspend/resume. Making hypercalls from within that
> > > code is thus incompatible with re-populating the hypercall table on resume
> > > since it transpites then Xen writes each byte in the page to 0xcc (int 3)
> > > before actually setting up the hypercall thunks. The only hypercall that the
> > > code was actually making was a SCHEDOP_yield and this is trivially replaced
> > > by an _mm_pause intrinsic which calls through to SCHEDOP_yield in the
> > > VMEXIT handler.
> > Thanks for the patch, I tested it, 3 save/restore without crash for now
> > and I not saw any regression, I'll report you if I'll see other crash.
> >
> > There is another problem with the save/restore on windows that is
> > driving me crazy for months:
> > with qxl vga all works good except after save/restore that make domU
> > "freeze" for 2-3 minutes on spice connect (always first time and
> > occasional the others), on windows shutdown/reboot and probably other
> > operations.
> > I'm unable to found the exactly cause of that, is there a way to know if
> > is caused by something unexpected in windows pv drivers or other xen
> > particular things in xen save/restore? (for example "interrupts disabled
> > on all CPUs apart from 0 to corale them across a suspend/resume" if I
> > understand good).
> Is it a network issue? The PV drivers should re-generate gratuitous ARPs and 
> IPv6 neighbour solicitations on resume so things should be ok but it would be 
> worth un-firewalling ICMP so you can check whether the VM is actually pingable.
Sorry if I not explain good, spice connect to dom0 as domU's vkvm 
instead vnc (and is better) and I use it also from thin client as it 
full features is better that rdp.
On windows domUs seems qxl works good as kvm except after xl restore 
when on spice connect, windows screen resolution change, windows 
shutdown and probably other things the domU "freeze" for 2-3 minutes and 
I'm unable to debug it.
> If the VM is really wedged though you can always use xen-hvmcrash from dom0 to 
> try to forcibly crash the domain such that Windows will create a MEMORY.DMP 
> that you can have a look at after reboot.
So if I understand good I can simulate a domU crash during the freeze to 
take a memory dump and see what happen during freeze?
>    Paul
>
> > Thanks for any reply and sorry for my bad english.
> >
> > > Signed-off-by: Paul Durrant<paul.durrant@xxxxxxxxxx>
> > > ---
> > >    src/xenbus/sync.c | 14 +++++++-------
> > >    1 file changed, 7 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/src/xenbus/sync.c b/src/xenbus/sync.c
> > > index 41ecbf9..78b5bef 100644
> > > --- a/src/xenbus/sync.c
> > > +++ b/src/xenbus/sync.c
> > > @@ -151,7 +151,7 @@ SyncWorker(
> > >                break;
> > >
> > >            if (SyncContext.DisableInterrupts[Cpu] == InterruptsDisabled) {
> > > -            SchedYield();
> > > +            _mm_pause();
> > >                KeMemoryBarrier();
> > >
> > >                continue;
> > > @@ -171,7 +171,7 @@ SyncWorker(
> > >                Attempts = 0;
> > >                while (SyncContext.Sequence == Sequence &&
> > >                       SyncContext.CompletionCount < CpuCount) {
> > > -                SchedYield();
> > > +                _mm_pause();
> > >                    KeMemoryBarrier();
> > >
> > >                    if (++Attempts > 1000) {
> > > @@ -213,7 +213,7 @@ SyncWorker(
> > >
> > >                while (SyncContext.Sequence == Sequence &&
> > >                       SyncContext.CompletionCount < CpuCount) {
> > > -                SchedYield();
> > > +                _mm_pause();
> > >                    KeMemoryBarrier();
> > >                }
> > >
> > > @@ -268,7 +268,7 @@ SyncCapture(
> > >        InterlockedIncrement(&SyncContext.CompletionCount);
> > >
> > >        while (SyncContext.CompletionCount < CpuCount) {
> > > -        SchedYield();
> > > +        _mm_pause();
> > >            KeMemoryBarrier();
> > >        }
> > >
> > > @@ -305,7 +305,7 @@ again:
> > >
> > >        Attempts = 0;
> > >        while (SyncContext.CompletionCount < CpuCount) {
> > > -        SchedYield();
> > > +        _mm_pause();
> > >            KeMemoryBarrier();
> > >
> > >            if (++Attempts > 1000) {
> > > @@ -366,7 +366,7 @@ SyncEnableInterrupts(
> > >        InterlockedIncrement(&SyncContext.CompletionCount);
> > >
> > >        while (SyncContext.CompletionCount < CpuCount) {
> > > -        SchedYield();
> > > +        _mm_pause();
> > >            KeMemoryBarrier();
> > >        }
> > >
> > > @@ -400,7 +400,7 @@ SyncRelease(
> > >        InterlockedIncrement(&SyncContext.CompletionCount);
> > >
> > >        while (SyncContext.CompletionCount < CpuCount) {
> > > -        SchedYield();
> > > +        _mm_pause();
> > >            KeMemoryBarrier();
> > >        }
> > >
> > > -- 2.1.1

_______________________________________________
win-pv-devel mailing list
win-pv-devel@xxxxxxxxxxxxxxxxxxxx
http://lists.xenproject.org/cgi-bin/mailman/listinfo/win-pv-devel