Re: [Xen-devel] [PATCH] xenfb: Fix overzealous ring test

[Samuel Thibault]

Wei Liu, on Mon 18 Apr 2016 15:40:15 +0100, wrote:
> This patch is already queued by Stefano.

Ah, sorry, I missed it.

Samuel

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Re: [Xen-devel] [PATCH] xenfb: Fix overzealous ring test

[Wei Liu]

On Mon, Apr 18, 2016 at 02:41:48PM +0200, Samuel Thibault wrote:
> From: Wei Liu 
> 
> pv-grub booting got broken with recent qemu-xen, due to
> ac0487e1d2ae811cd4d035741a109a4ecfb013f1 ('xenfb.c: avoid expensive loops
> when prod <= out_cons')
> 
> prod - out_cons can actually be XENFB_OUT_RING_LEN when the ring is exactly
> full, this is a normal condition and should not be excluded.
> 
> From: Wei Liu 
> Signed-off-by: Samuel Thibault 
> Tested-by: Hao Xudong 

Hi Samuel,

This patch is already queued by Stefano. After it has been applied
upstream we will backport it to our own tree.

Wei.

> ---
>  hw/display/xenfb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
> index 40b096a..9866dfd 100644
> --- a/hw/display/xenfb.c
> +++ b/hw/display/xenfb.c
> @@ -775,7 +775,7 @@ static void xenfb_handle_events(struct XenFB *xenfb)
>  
>  prod = page->out_prod;
>  out_cons = page->out_cons;
> -if (prod - out_cons >= XENFB_OUT_RING_LEN) {
> +if (prod - out_cons > XENFB_OUT_RING_LEN) {
>  return;
>  }
>  xen_rmb();   /* ensure we see ring contents up to prod */
> -- 
> 2.8.0.rc3
> 

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[Xen-devel] [PATCH] xenfb: Fix overzealous ring test

[Samuel Thibault]

From: Wei Liu 

pv-grub booting got broken with recent qemu-xen, due to
ac0487e1d2ae811cd4d035741a109a4ecfb013f1 ('xenfb.c: avoid expensive loops
when prod <= out_cons')

prod - out_cons can actually be XENFB_OUT_RING_LEN when the ring is exactly
full, this is a normal condition and should not be excluded.

From: Wei Liu 
Signed-off-by: Samuel Thibault 
Tested-by: Hao Xudong 
---
 hw/display/xenfb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
index 40b096a..9866dfd 100644
--- a/hw/display/xenfb.c
+++ b/hw/display/xenfb.c
@@ -775,7 +775,7 @@ static void xenfb_handle_events(struct XenFB *xenfb)
 
 prod = page->out_prod;
 out_cons = page->out_cons;
-if (prod - out_cons >= XENFB_OUT_RING_LEN) {
+if (prod - out_cons > XENFB_OUT_RING_LEN) {
 return;
 }
 xen_rmb(); /* ensure we see ring contents up to prod */
-- 
2.8.0.rc3


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