Re: [PATCH] Don't map nested_vmcb on INTERCEPT_MSR_PROT

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On Sat, Sep 05, 2009 at 12:59:26AM +0200, Alexander Graf wrote:
>
> Am 04.09.2009 um 19:05 schrieb Marcelo Tosatti <mtosatti@xxxxxxxxxx>:
>
>> On Thu, Sep 03, 2009 at 04:51:52PM +0200, Alexander Graf wrote:
>>> Thanks to Joerg's previous series of cleanups, we now have almost all
>>> information we need to decide what to do on #VMEXIT because we get
>>> the variables from the VMCB on VMRUN.
>>>
>>> Unfortunately there's one piece that slipped through the conversion,
>>> namely the MSR intercept which still tries to map the nested VMCB
>>> to find out if MSRs are intercepted.
>>>
>>> So let's use the cached value, removing the need for two atomic maps
>>> (which breaks anyways) and fix an oops along the way.
>>>
>>> CC: Joerg Roedel <joerg.roedel@xxxxxxx>
>>> Signed-off-by: Alexander Graf <agraf@xxxxxxx>
>>
>> Applied, thanks.
>>
>> BTW, why nested_svm_map takes mmap_sem? Thats looks wrong.
>
> Hm, good question.
>
> As long as it's an atomic section that only touches vcpu local data  
> there's no need to lock at all, right?

Yes. gfn_to_page / get_user_pages will grab mmap_sem if required. Can
you please send a patch to drop it from nested_svm_map?

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