Re: [Xen-devel] [PATCH] hvmloader / qemu-xen: Getting rid of resource conflict for OpRegion.

[Keir Fraser <keir@xxxxxxx>]

On 20/12/2012 13:31, "G.R." <firemeteor@xxxxxxxxxxxxxxxxxxxxx> wrote:

> If concern is about security, the same argument should apply to the
> first page (the portion before the page offset).
> The problem is that I have no idea what is around the mapped page. Not
> sure who has the knowledge.

Well we can't do better than mapping some whole number of pages, really.
Unless we trap to qemu on every access. I don't think we'd go there unless
there really were a known security issue. But mapping only the exact number
of pages we definitely need is a good principle.

> What's the standard flow to handle such map with offset?
> I expect this to be a common case, since the ioremap function in linux
> kernel accept this.

map_size = ((host_opregion & 0xfff) + 8096 + 0xfff) >> 12

Possibly with suitable macros used instead of magic numbers (e.g., XC_PAGE_*
and a macro for the opregion size).

 -- Keir



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