Re: [Xen-devel] Please revert / review 077fc1c04d70ef1748ac2daa6622b3320a1a004c

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Matthias wrote on 2014-06-11:
> Through bisecting, I found out that the commit
> http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=077fc1c04d70ef1748
> ac 2daa6622b3320a1a004c causes a BSOD on my system when using vga
> passthrough with a AMD card (The usual 0x116 BSOD atikmdag.sys throws).
> Reverting this commit locally fixes this issue completely and
> reproducible, even with newer 4.5-versions of xen. Behaviour is
> reproducible with several 3.11+ kernels I tested (haven't tested <3.11
> ones).
> 
> 
> So it would be great if someone could review or revert this commit. I
> don't have any deeper knowledge about this commit or what it actually
> does, but would be happy to test possible fixes, so let me know if I
> can be of any help or should provide more information.

Hi Matthias,

The patch only impacts the log dirty path. I don't know why it will cause GFX 
pass through fail. So can you have a check that whether log dirty mode is used 
in your case? The following patch will simply print the message whether log 
dirty mode is using, maybe you can have a try.

diff --git a/xen/arch/x86/mm/paging.c b/xen/arch/x86/mm/paging.c
index ab5eacb..26fea12 100644
--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -167,6 +167,8 @@ void paging_free_log_dirty_bitmap(struct domain *d)
 int paging_log_dirty_enable(struct domain *d, bool_t log_global)
 {
     int ret;
+    
+    printk("testing: enable log dirty mode\n");
 
     if ( paging_mode_log_dirty(d) )
         return -EINVAL;


BTW, please provide the xen log and qemu log.

Best regards,
Yang


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