Re: [PATCH v2 16/17] kvm: x86: Rework identity map and TSS setup for larger BIOS sizes

Jan Kiszka
2011-01-03T16:52:35Z

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Am 03.01.2011 17:06, Avi Kivity wrote:
> On 01/03/2011 10:33 AM, Jan Kiszka wrote:
>> From: Jan Kiszka<jan.kiszka@siemens.com>
>>
>> First of all, we only need this EPT identity and TSS reservation on
>> Intel CPUs.
>
> kvm-amd will ignore it just fine. I'd like to keep arch differences
> away from userspace.

And I would prefer to avoid needlessly cluttering the physical guest
address space where not needed. Long term, we could even give user space
a hint (unless it can test it directly) that this workaround is no
longer needed as the host Intel CPU supports true real mode.

>
>> Then, in order to support loading BIOSes> 256K, reorder the
>> code, adjusting the base if the kernel supports moving the identity map.
>> We can drop the check for KVM_CAP_SET_TSS_ADDR as we already depend on
>> much newer features.
>
> There is no ordering on kvm features. Each can come and go as it pleases.
>

Well, at least this is not how kvm upstream works so far.

Jan

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