Re: [Xen-devel] [PATCH 0/2] MTRR/PAT virtualization

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

The second patch is a bit of a hack-and-slash job. New memory-type
virtualisation code should go in a new file, instead of being put in host
MTRR management files (which are mostly unmodified from Linux anyway, and
shouldn't deviate more than necessary). There are various other one-line
changes in various MTRR source files that are unexplained (e.g., mask
changes from |0xf00 to |0x7ff). Initialisation of guest MTRR state will need
to be moved to hvmloader -- we do not call setvcpucontext for HVM guests any
more, so the current hack won't work with current xen-unstable. Coding style
needs cleaning up (looks like there is some spaces vs. tabs mixing up going
on).

  -- Keir

On 8/10/07 08:34, "Su, Disheng" <disheng.su@xxxxxxxxx> wrote:

> Hi,
> The following 2 patches add basic MTRR/PAT support into
> hypervisor. When vt-d enabled, direct IO and RAM
> could be mapped to different cache attribute, such as UC or WC, which
> will bring some trouble.
> xen.patch: some data structures of MTRR in xen are exported.
> mtrr_pat.patch: The basic idea is listed below:
>           a. MTRR/PAT MSRs are per vcpu. The value of guest MTRR is
> initialized in host, after guest E820 table is build. The value of guest
> PAT is initialized as default. The host PAT is initialized to cover all
> the page attributes.  
>           b. The guest page attribute is virtualized through shadow page
> attribute. First, get the effective guest page attribute, by calculating
> from the combination of guest MTRR/PAT. Then the shadow page attribute
> is calculated from effective guest page attribute and host MTRR. If
> conflict occurs(e.g effective guest page attribute is WB, host MTRR of
> this range is UC, can't set this page attribute as guest required), set
> this range as UC. Some lookup tables are added to accelerate above
> procedure.
> 
> Signed-off-by: Disheng Su <disheng.su@xxxxxxxxx>
> 
> Best Regards,
> Disheng, Su
> 
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