Re: [Xen-devel] GPU passthrough performance regression in >4GB vms due to XSA-60 changes

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.05.14 at 13:38, <JBeulich@xxxxxxxx> wrote:
>>>> On 16.05.14 at 13:18, <tomasz.wroblewski@xxxxxxxxx> wrote:
>>> If I coded up a patch to deal with this on -unstable, would you be
>>> able to test that?
>> Willing to give it a go (xen major version updates are often problematic 
>> to do though so can't promise success). What would your patch be doing? 
>> Adding entries to MTRR for the relocated regions?
> 
> This and properly declare the region in ACPI's _CRS. For starters I'll
> probably try keeping the WB default overlaid with UC variable ranges,
> as that's going to be the less intrusive change.

Okay here are two patches - the first to deal with the above mentioned
items, and the second to further increase correctness and at once
shrink the number of MTRR regions needed.

Afaict they apply equally well to stable-4.3, master, and staging.

But to be honest I don't expect any performance improvement, all
I'd expect is that BARs relocated above 4Gb would now get treated
equally to such below 4Gb - UC in all cases.

Jan

Attachment: hvmloader-PCI-above-4G.patch
Description: Text document

Attachment: hvmloader-UC-up-to-4G.patch
Description: Text document

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