Re: [Xen-devel] [PATCH] svm: support VMCB cleanbits

[Keir Fraser <keir@xxxxxxx>]

On 15/12/2010 23:04, "Huang2, Wei" <Wei.Huang2@xxxxxxx> wrote:

> Hi Keir,
> 
> Thanks for putting up this patch. I think the comments you made are correct
> after reading the spec again. Christoph and I misread some APM content. :-(

No problem then. It would be good to know that the applied patch works and
with the same performance win as you saw with your original patch.

 -- Keir

> Thanks again,
> -Wei
> 
> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Keir Fraser
> Sent: Wednesday, December 15, 2010 10:56 AM
> To: Egger, Christoph; Tim Deegan
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] [PATCH] svm: support VMCB cleanbits
> 
> On 15/12/2010 12:36, "Christoph Egger" <Christoph.Egger@xxxxxxx> wrote:
> 
>> On Wednesday 15 December 2010 12:27:51 Tim Deegan wrote:
>>> This seems to change the logic so it doesn't clear the intercepts if
>>> debug_state == 0.  Is that OK?
>> 
>> No, that's not ok. I fixed that in the new patch.
>> 
>>> More generally, I'm not sure I like having all the VMCB accessor
>>> functions in files called "cleanbits" -- wouldn't it make sense to have
>>> all that in the vmcb files so people will see them and know to use them?
>>> You could rename the actual vmcb fields as well to catch anyone writing
>>> them directly, e.g. in forward-ported patches.
>> 
>> I renamed the 'svmcleanbits.[ch]' files to 'vmc_funcs.[ch]'
>> 
>> Thanks for your review.
> 
> I went through this patch quite brutally when I applied it (c/s 22546). In
> particular I made the VMCB field accessor functions more consistent in name
> and semantics, and pulled out their implementations into a common macro to
> make the code clearer.
> 
> There should be no significant changes compared with your patch *EXCEPT*:
>  1. Updates to the MSR and I/O bitmaps do not affect clear bits
>  2. Updates to lbr_control.enable do not affect clear bits
>  3. Updates to debugctlmsr *do* affect clear bits
> 
> In the above I am following what is described in AMD Volume 2 Section
> 15.15.3 "VMCB Clean Field".
> 
> I note that the MSRPM_BASE and IOPM_BASE fields are listed as cacheable, but
> *no* mention is made of caching the bitmap contents.
> 
> Also, bit 10 (LBR) has debugctlmsr listed as cacheable, but again *no*
> mention is made of the lbr_control.enable bit flag.
> 
> If any of the above is wrong, then: (a) the reference manual should be
> fixed; (b) I would accept a fixup patch, with a patch description
> explaininbg why behaviour is deviating from cleanbits behaviour describved
> in the latest version of the AMD reference manuals.
> 
>  -- Keir
> 
>> Signed-off-by: Wei Huang <Wei.Huang2@xxxxxxx>
>> Signed-off-by: Christoph Egger <Christoph.Egger@xxxxxxx>
>> 
>> Christoph
>> 
> 
> 
> 
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> 
> 



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