From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Junaid Shahid <junaids@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 7/9] KVM: nSVM: implement nested_svm_load_cr3() and use it for host->guest switch
Date: Fri, 10 Jul 2020 14:30:36 +0200 [thread overview]
Message-ID: <878sfrv9g3.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <353dc97c-9754-68f9-6fb7-13671995e0a2@redhat.com>
Paolo Bonzini <pbonzini@redhat.com> writes:
> On 10/07/20 13:40, Vitaly Kuznetsov wrote:
>> Hm, it seems I missed svm_set_nested_state() path
>> completely. Surprisingly, state_test didn't fail)
>>
>> I'm struggling a bit to understand why we don't have kvm_set_cr3() on
>> svm_set_nested_state() path: enter_svm_guest_mode() does it through
>> nested_prepare_vmcb_save() but it is skipped in svm_set_nested_state().
>> Don't we need it at least for !npt_enabled case?
>
> In svm_set_nested_state you'll have CR3 already set to the right value.
> On the source, KVM_GET_SREGS returns the vmcb12's CR3 and it is already
> restored with KVM_SET_SREGS on the destination before set_nested_state.
>
> So, only the nested_cr3 has to be set.
>
Ah, thanks, so it seems there is no need to merge nested_svm_load_cr3()
(former kvm_set_cr3()) with nested_svm_init_mmu_context() in a new
nested_svm_init_mmu() as we'll only need the latter on
svm_set_nested_state(). We can just move nested_svm_load_cr3() out of
nested_prepare_vmcb_save() to enter_svm_guest_mode().
--
Vitaly
next prev parent reply other threads:[~2020-07-10 12:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-09 14:53 [PATCH v3 0/9] KVM: nSVM: fixes for CR3/MMU switch upon nested guest entry/exit Vitaly Kuznetsov
2020-07-09 14:53 ` [PATCH v3 1/9] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov
2020-07-09 14:53 ` [PATCH v3 2/9] KVM: nSVM: stop dereferencing vcpu->arch.mmu to get the context in kvm_init_shadow{,_npt}_mmu() Vitaly Kuznetsov
2020-07-09 17:47 ` Paolo Bonzini
2020-07-09 14:53 ` [PATCH v3 3/9] KVM: nSVM: reset nested_run_pending upon nested_svm_vmrun_msrpm() failure Vitaly Kuznetsov
2020-07-09 17:48 ` Paolo Bonzini
2020-07-09 14:53 ` [PATCH v3 4/9] KVM: nSVM: prepare to handle errors from enter_svm_guest_mode() Vitaly Kuznetsov
2020-07-09 14:53 ` [PATCH v3 5/9] KVM: nSVM: introduce nested_svm_load_cr3() Vitaly Kuznetsov
2020-07-09 14:53 ` [PATCH v3 6/9] KVM: nSVM: move kvm_set_cr3() after nested_svm_uninit_mmu_context() Vitaly Kuznetsov
2020-07-09 17:51 ` Paolo Bonzini
2020-07-09 14:53 ` [PATCH v3 7/9] KVM: nSVM: implement nested_svm_load_cr3() and use it for host->guest switch Vitaly Kuznetsov
2020-07-09 17:57 ` Paolo Bonzini
2020-07-09 17:59 ` Paolo Bonzini
2020-07-10 11:40 ` Vitaly Kuznetsov
2020-07-10 12:08 ` Paolo Bonzini
2020-07-10 12:30 ` Vitaly Kuznetsov [this message]
2020-07-09 14:53 ` [PATCH v3 8/9] KVM: nSVM: use nested_svm_load_cr3() on guest->host switch Vitaly Kuznetsov
2020-07-09 14:53 ` [PATCH v3 9/9] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() Vitaly Kuznetsov
2020-07-09 18:01 ` [PATCH v3 0/9] KVM: nSVM: fixes for CR3/MMU switch upon nested guest entry/exit Paolo Bonzini
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