Re: [Xen-devel] Regression in OSSTest Windows install test case

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Jul 16, 2015 at 10:06:35AM +0100, Paul Durrant wrote:
> > -----Original Message-----
> > From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx]
> > Sent: 16 July 2015 10:03
> > To: Paul Durrant
> > Cc: Wei Liu; xen-devel@xxxxxxxxxxxxxxxxxxxx; Jan Beulich; Andrew Cooper
> > Subject: Re: Regression in OSSTest Windows install test case
> > 
> > On Thu, Jul 16, 2015 at 09:39:42AM +0100, Paul Durrant wrote:
> > [...]
> > > I think I found the semantic difference. Prior to this patch it would seem
> > that stdvga buffered writes even when not in stdvga mode. When I tested
> > your config (using cirrus), windows drops out of stdvga quite early in boot
> > which slows down the splash screen to a crawl. When I just uncommented
> > the single line 'stdvga=1' then I got through the splash screen several 
> > orders
> > of magnitude faster.
> > > So, I think this (compile tested only) incremental patch should fix the 
> > > test:
> > >
> > > diff --git a/xen/arch/x86/hvm/stdvga.c b/xen/arch/x86/hvm/stdvga.c
> > > index 6d22b22..d528155 100644
> > > --- a/xen/arch/x86/hvm/stdvga.c
> > > +++ b/xen/arch/x86/hvm/stdvga.c
> > > @@ -441,7 +441,7 @@ static int stdvga_mem_write(const struct
> > hvm_io_handler *han
> > >      };
> > >      struct hvm_ioreq_server *srv;
> > >
> > > -    if ( !s->cache )
> > > +    if ( !s->cache || !s->stdvga )
> > >          goto done;
> > >
> > >      /* Intercept mmio write */
> > > @@ -503,9 +503,6 @@ static bool_t stdvga_mem_accept(const struct
> > hvm_io_handler
> > >
> > >      spin_lock(&s->lock);
> > >
> > > -    if ( !s->stdvga )
> > > -        goto reject;
> > > -
> > >      if ( p->dir == IOREQ_WRITE && p->count > 1 )
> > >      {
> > >          /*
> > > @@ -526,7 +523,7 @@ static bool_t stdvga_mem_accept(const struct
> > hvm_io_handler
> > >
> > >          goto reject;
> > >      }
> > > -    else if ( p->dir == IOREQ_READ && !s->cache )
> > > +    else if ( p->dir == IOREQ_READ && !s->cache && !s->stdvga )
> > >          goto reject;
> > >
> > >      /* s->lock intentionally held */
> > >
> > > I can't say that I like the idea of unconditionally buffering VRAM 
> > > writes, but
> > I'll test patch and post it.
> > >
> > 
> > Thank you for the fix. It fixes the problem for me.
> 
> Cool. There's actually a small bug-ette in it. The line:
> 
> else if ( p->dir == IOREQ_READ && !s->cache && !s->stdvga )
> 
> should be:
> 
> else if ( p->dir == IOREQ_READ && (!s->cache || !s->stdvga) )
> 
> I don't think that will affect the behaviour in this case though since I very 
> much doubt Windows is reading VRAM at this stage. Could you perhaps re-test 
> with that change?
> 

It works. So again:

 Tested-by: Wei Liu <wei.liu2@xxxxxxxxxx>

> Cheers,
> 
>   Paul
> 
> > 
> > Tested-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > 
> > >   Paul
> > >
> > >
> > 
> > 
> > 
> > > > Wei.

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