Re: [Qemu-devel] Re: Another SIGFPE in display code, now in cirrus

[Avi Kivity <avi@redhat.com>]

On 05/12/2010 09:11 PM, Stefano Stabellini wrote:
> On Wed, 12 May 2010, Jamie Lokier wrote:
>    
>> Stefano Stabellini wrote:
>>      
>>> On Wed, 12 May 2010, Avi Kivity wrote:
>>>        
>>>> It's useful if you have a one-line horizontal pattern you want to
>>>> propagate all over.
>>>>          
>>>
>>> It might be useful all right, but it is not entirely clear what the
>>> hardware should do in this situation from the documentation we have, and
>>> certainly the current state of the cirrus emulation code doesn't help.
>>>        
>> It's quite a reasonable thing for hardware to do, even if not documented.
>> It would be surprising if the hardware didn't copy the one-line pattern.
>>      
>
> All right then, you convinced me :)
>
> This is my proposed solution, however it is untested with Windows NT.
>
>
> Signed-off-by: Stefano Stabellini<stefano.stabellini@eu.citrix.com>
>
> ---
>
>
>
> diff --git a/hw/cirrus_vga.c b/hw/cirrus_vga.c
> index 9f61a01..a7f0d3c 100644
> --- a/hw/cirrus_vga.c
> +++ b/hw/cirrus_vga.c
> @@ -676,15 +676,17 @@ static void cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
>       int sx, sy;
>       int dx, dy;
>       int width, height;
> +    uint32_t start_addr, line_offset, line_compare;
>       int depth;
>       int notify = 0;
>
>       depth = s->vga.get_bpp(&s->vga) / 8;
>       s->vga.get_resolution(&s->vga,&width,&height);
> +    s->vga.get_offsets(&s->vga,&line_offset,&start_addr,&line_compare);
>
>       /* extra x, y */
> -    sx = (src % ABS(s->cirrus_blt_srcpitch)) / depth;
> -    sy = (src / ABS(s->cirrus_blt_srcpitch));
> +    sx = (src % line_offset) / depth;
> +    sy = (src / line_offset);
>    

Does anything prevent the guest from programming the CRTC display pitch 
to 0?

>       dx = (dst % ABS(s->cirrus_blt_dstpitch)) / depth;
>       dy = (dst / ABS(s->cirrus_blt_dstpitch));
>
> @@ -725,18 +727,23 @@ static void cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
>   		      s->cirrus_blt_dstpitch, s->cirrus_blt_srcpitch,
>   		      s->cirrus_blt_width, s->cirrus_blt_height);
>
> -    if (notify)
> -	qemu_console_copy(s->vga.ds,
> -			  sx, sy, dx, dy,
> -			  s->cirrus_blt_width / depth,
> -			  s->cirrus_blt_height);
> -
> -    /* we don't have to notify the display that this portion has
> -       changed since qemu_console_copy implies this */
> -
> -    cirrus_invalidate_region(s, s->cirrus_blt_dstaddr,
> -				s->cirrus_blt_dstpitch, s->cirrus_blt_width,
> -				s->cirrus_blt_height);
> +     if (ABS(s->cirrus_blt_dstpitch) != line_offset ||
> +             ABS(s->cirrus_blt_srcpitch) != line_offset) {
> +             /* this is not going to happen very often */
> +             vga_hw_invalidate();
>    

I think we need to consider only dstpitch for a full invalidate.  We 
might be copying an offscreen bitmap into the screen, and srcpitch is 
likely to be the bitmap width instead of the screen pitch.


> +     } else {
> +         if (notify)
> +             /* we don't have to notify the display that this portion has
> +                changed since qemu_console_copy implies this */
> +             qemu_console_copy(s->vga.ds,
> +                               sx, sy, dx, dy,
> +                               s->cirrus_blt_width / depth,
> +                               s->cirrus_blt_height);
> +         else
> +             cirrus_invalidate_region(s, s->cirrus_blt_dstaddr,
> +                                      s->cirrus_blt_dstpitch, s->cirrus_blt_width,
> +                                      s->cirrus_blt_height);
> +     }
>   }
>
>   static int cirrus_bitblt_videotovideo_copy(CirrusVGAState * s)
> diff --git a/hw/cirrus_vga_rop.h b/hw/cirrus_vga_rop.h
> index 39a7b72..80f135b 100644
> --- a/hw/cirrus_vga_rop.h
> +++ b/hw/cirrus_vga_rop.h
> @@ -32,10 +32,10 @@ glue(cirrus_bitblt_rop_fwd_, ROP_NAME)(CirrusVGAState *s,
>       dstpitch -= bltwidth;
>       srcpitch -= bltwidth;
>
> -    if (dstpitch<  0 || srcpitch<  0) {
> -        /* is 0 valid? srcpitch == 0 could be useful */
> +    if (dstpitch<  0)
>           return;
> -    }
> +    if (srcpitch<  0)
> +        srcpitch = 0;
>    

Why?



-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.