Re: [PATCH 2/3] KVM: VMX: Simplify pdptr and cr3 management

[Avi Kivity <avi@redhat.com>]

Sheng Yang wrote:
> On Monday 01 June 2009 21:22:02 Avi Kivity wrote:
>   
>> Instead of reading the PDPTRs from memory after every exit (which is slow
>> and wrong, as the PDPTRs are stored on the cpu), sync the PDPTRs from
>> memory to the VMCS before entry, and from the VMCS to memory after exit.
>> Do the same for cr3.
>>
>>     
>
> Thanks for fixing!
>
> After review my original code, I found a potential bug. For SDM 3B have this:
>
> 23.3.4 Saving Non-Register State
> ...
> If the logical processor supports the 1-setting of the “enable EPT” VM-
> execution control, values are saved into the four (4) PDPTE fields as follows:
> — If the “enable EPT” VM-execution control is 1 and the logical processor was
> using PAE paging at the time of the VM exit, the PDPTE values currently in use
> are saved:
> • The values saved into bits 11:9 of each of the fields is undefined.
> • If the value saved into one of the fields has bit 0 (present) clear, the 
> value saved into bits 63:1 of that field is undefined. That value need not
> correspond to the value that was loaded by VM entry or to any value that
> might have been loaded in VMX non-root operation.
> • If the value saved into one of the fields has bit 0 (present) set, the value
> saved into bits 63:12 of the field is a guest-physical address.
> — If the “enable EPT” VM-execution control is 0 or the logical processor was 
> not using PAE paging at the time of the VM exit, the values saved are 
> undefined.
>
> But drop the ept_load_pdptrs() when exit and add it in cr0 handling result in 
> Windows PAE guest hang on boot. I am checking it now. Any thoughts?...
>   

You mean with the new code?  What version of Windows exactly?

I'll check it out, though EPTs are a little hard to find here.

-- 
error compiling committee.c: too many arguments to function