Re: [Xen-devel] OVMF very slow on AMD

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 07/27/2016 07:35 AM, Anthony PERARD wrote:
> On Wed, Jul 27, 2016 at 12:08:04PM +0100, Anthony PERARD wrote:
>> I can try to describe how OVMF is setting up the memory.
> From the start of the day:
> setup gdt
> cr0 = 0x40000023

I think this is slightly odd, with bit 30 (cache disable) set. I'd
suspect that this would affect both Intel and AMD though.

Can you try clearing this bit?

-boris

>
> jump to 32bit
> cr4 = 0x640
>
> setup page tables:
> page directory attributes: (PAGE_ACCESSED + PAGE_READ_WRITE + PAGE_PRESENT)
> page tables attributes: (PAGE_2M_MBO + PAGE_ACCESSED + PAGE_DIRTY + 
> PAGE_READ_WRITE + PAGE_PRESENT)
> I think they map the all 4GB with 2MB pages.
> set cr3.
>
> enable PAE
> set LME
> set PG
>
> jump to 64bit
>
> I think that's it, before running this painfully slow decompression
> function.
>
> Is there something wrong, or maybe missing? Is the hypervisor or maybe
> the hardware does not do the right thing?
>
> Thanks,
>



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