Re: [PATCH 2/2] hw/display/vmware_vga: do not discard screen updates

[Carwyn Ellis]

> On 4 Jan 2022, at 12:23, Gerd Hoffmann <kraxel@redhat.com> wrote:
> 
>  Hi,
> 
>> This change firstly increases the screen update FIFO size to ensure it's
>> large enough to accomodate all updates deferred in a given screen
>> refresh cycle.
> 
> How do you know it's large enough?
> 
>> @@ -385,7 +385,14 @@ static inline void vmsvga_update_rect_delayed(struct 
>> vmsvga_state_s *s,
>> {
>>     struct vmsvga_rect_s *rect = &s->redraw_fifo[s->redraw_fifo_last++];
>> 
>> -    s->redraw_fifo_last &= REDRAW_FIFO_LEN - 1;
>> +    if (s->redraw_fifo_last >= REDRAW_FIFO_LEN) {
>> +        VMWARE_VGA_DEBUG("%s: Discarding updates - FIFO length %d 
>> exceeded\n",
>> +            "vmsvga_update_rect_delayed",
>> +            REDRAW_FIFO_LEN
> 
> Hmm, apparently you don't know ;)
> 
> How about just calling vmsvga_update_rect_flush()
> when the fifo is (almost) full?

Yeah will give that a shot. Wasn’t sure how it’d play so did the simplest thing 
possible.

> 
> Which guest do you use btw?  I'm kind-of surprised this is still being
> used even though it hasn't seen any development (beside fixing a bug now
> and then) for a decade or so and the feature gap to recent vmware is
> huge ...
> 

This is an old vmware vm that rarely gets used. Figured I’d see if I could get 
it working over the holidays after making the move off an intel mac to m1, and 
noticed the issue with the output. In this case using the already configured 
vmware drivers was the least worst option.

> take care,
>  Gerd
> 

Cheers
Carwyn