Re: [Xen-devel] [PATCH] xen/grant-table: correctly initialize grant table version 1

[Matt Wilson <msw@xxxxxxxxxx>]

On Thu, Dec 20, 2012 at 11:42:05AM +0800, ANNIE LI wrote:
> 
> Thanks for posting this.
> This is caused by not initializing grant_table_version in
> gnttab_init() before gnttab_resume(). How about only adding
> gnttab_request_version() and BUG_ON() to check grant_table_version
> in gnttab_init(), then no need to change GREFS_PER_GRANT_FRAME into
> grefs_per_grant_frame and add more BUG_ON() to check
> grefs_per_grant_frame?
> 
> For example, in gnttab_init()
> ....
> 
> +gnttab_request_version();
> +BUG_ON(grant_table_version == 0);
> 

Having GREFS_PER_GRANT_FRAME evaluate a conditional every time it's
used makes me uneasy. I know I added excessive BUG_ON()s, but my
intent was just to be defensive. GREFS_PER_GRANT_FRAME is used in the
conditional part of for (...) loops in several locations. I think it's
better to have this as a variable instead of a conditional expression.

Matt

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