Re: [PATCH] KVM: nVMX: Replace kvm_set_cr0 with vmx_set_cr0 in load_vmcs12_host_state

[Jan Kiszka <jan.kiszka@web.de>]

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On 2013-02-24 11:11, Avi Kivity wrote:
> On Sun, Feb 24, 2013 at 11:40 AM, Jan Kiszka <jan.kiszka@web.de> wrote:
>>>>> We have the same problem in KVM_SET_SREGS.
>>>>
>>>> I don't see the problem. kvm_arch_vcpu_ioctl_set_sregs open-codes the
>>>> state update, not applying any transition checks.
>>>
>>> That's the problem.  We have this open coding in three different
>>> places (KVM_SET_SREGS, nvmx, nsvm).
>>>
>>> It's not as if vmx_set_cr0() is defined as "kvm_set_cr0() without the
>>> transition checks".
>>
>> ...and without mmu updates. The latter is done via or after the closing
>> cr3 update. Interestingly, nsvm does not perform kvm_set_cr3 on vmexit
>> when in npt mode. Seems things aren't that regular.
> 
> We do want the mmu updates.  Of course they can't be attached to
> kvm_set_cr0_without_the_checks() since there is cross-register
> dependencies.
> 
> Option 1 is kvm_set_multiple_cr().  This does the checks and updates,
> but only after all registers are updated.
> Option 2 is kvm_begin_cr_transaction()/kvm_commit_cr_transaction().
> Prettier and more flexible, but a more complicated to implement.
> 

The only thing that these three use case truly have in common is the
closing kvm_mmu_reset_context. Maybe nvmx and nsvm can share a bit more.
But let's get nVMX right first, then think about sharing.

Jan


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