linux-kernel - Re: [PATCH 10/12] KVM: MMU: load new PGD after the shadow MMU is initialized

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Message-ID: <56ee0380-3717-b150-c674-08f76b6e295b@redhat.com>
Date:   Fri, 11 Feb 2022 18:47:53 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        vkuznets@...hat.com, mlevitsk@...hat.com, dmatlack@...gle.com
Subject: Re: [PATCH 10/12] KVM: MMU: load new PGD after the shadow MMU is
 initialized

On 2/11/22 18:45, Sean Christopherson wrote:
> On Wed, Feb 09, 2022, Paolo Bonzini wrote:
>> Now that __kvm_mmu_new_pgd does not look at the MMU's root_level and
>> shadow_root_level anymore, pull the PGD load after the initialization of
>> the shadow MMUs.
>>
>> Besides being more intuitive, this enables future simplifications
>> and optimizations because it's not necessary anymore to compute the
>> role outside kvm_init_mmu.  In particular, kvm_mmu_reset_context was not
>> attempting to use a cached PGD to avoid having to figure out the new role.
>> It will soon be able to follow what nested_{vmx,svm}_load_cr3 are doing,
>> and avoid unloading all the cached roots.
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
>> ---
> 
> If you add a sanity check as described in the other thread[*],
> 
> Reviewed-by: Sean Christopherson <seanjc@...gle.com>

It's not as easy as I thought, but it becomes almost trivial with the 
CPU/MMU role refactoring.  I'll get that posted as soon as I can push a 
final-ish version of this one to kvm/queue.

Paolo