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From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v2 17/18] KVM: x86: flush TLB separately from MMU reset
Date: Mon, 21 Feb 2022 16:01:10 +0100	[thread overview]
Message-ID: <3863d7f1-a551-129d-d218-c4cce40041d3@redhat.com> (raw)
In-Reply-To: <YhAyX+Bc3x4+ZMTG@google.com>

On 2/19/22 00:57, Sean Christopherson wrote:
> I appreciate the cleverness in changing only a single like, but I think both
> pieces warrant a mention.  How 'bout this, to squeak by with two lines?
> 
> 	/*
> 	 * Reset the MMU and flush the TLB if paging was enabled (INIT only, as
> 	 * CR0 is currently guaranteed to be '0' prior to RESET).  Unlike the

Let's just make it clearer:

          * On the standard CR0/CR4/EFER modification paths, there are several
          * complex conditions determining whether the MMU has to be reset and/or
          * which PCIDs have to be flushed.  However, CR0.WP and the paging-related
          * bits in CR4 and EFER are irrelevant if CR0.PG was '0'; and a reset+flush
          * is needed anyway if CR0.PG was '1' (which can only happen for INIT, as
          * CR0 will be '0' prior to RESET).  So we only need to check CR0.PG here.

Paolo

  reply	other threads:[~2022-02-21 15:01 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-17 21:03 [PATCH v2 00/18] KVM: MMU: do not unload MMU roots on all role changes Paolo Bonzini
2022-02-17 21:03 ` [PATCH v2 01/18] KVM: x86: host-initiated EFER.LME write affects the MMU Paolo Bonzini
2022-02-18 17:08   ` Sean Christopherson
2022-02-18 17:26     ` Paolo Bonzini
2022-02-23 13:40   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 02/18] KVM: x86: do not deliver asynchronous page faults if CR0.PG=0 Paolo Bonzini
2022-02-18 17:12   ` Sean Christopherson
2022-02-23 14:07   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 03/18] KVM: x86/mmu: WARN if PAE roots linger after kvm_mmu_unload Paolo Bonzini
2022-02-18 17:14   ` Sean Christopherson
2022-02-18 17:23     ` Paolo Bonzini
2022-02-23 14:11       ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 04/18] KVM: x86/mmu: avoid NULL-pointer dereference on page freeing bugs Paolo Bonzini
2022-02-18 17:15   ` Sean Christopherson
2022-02-23 14:12   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 05/18] KVM: x86/mmu: use struct kvm_mmu_root_info for mmu->root Paolo Bonzini
2022-02-23 14:39   ` Maxim Levitsky
2022-02-23 15:42     ` Sean Christopherson
2022-02-17 21:03 ` [PATCH v2 06/18] KVM: x86/mmu: do not consult levels when freeing roots Paolo Bonzini
2022-02-18 17:27   ` Sean Christopherson
2022-02-23 14:59   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 07/18] KVM: x86/mmu: Do not use guest root level in audit Paolo Bonzini
2022-02-18 18:37   ` Sean Christopherson
2022-02-18 18:46     ` Paolo Bonzini
2022-02-23 15:02       ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 08/18] KVM: x86/mmu: do not pass vcpu to root freeing functions Paolo Bonzini
2022-02-18 18:39   ` Sean Christopherson
2022-02-23 15:16   ` Maxim Levitsky
2022-02-23 15:48     ` Sean Christopherson
2022-02-17 21:03 ` [PATCH v2 09/18] KVM: x86/mmu: look for a cached PGD when going from 32-bit to 64-bit Paolo Bonzini
2022-02-18 18:08   ` Sean Christopherson
2022-02-23 16:01   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 10/18] KVM: x86/mmu: load new PGD after the shadow MMU is initialized Paolo Bonzini
2022-02-18 23:59   ` Sean Christopherson
2022-02-23 16:20   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 11/18] KVM: x86/mmu: Always use current mmu's role when loading new PGD Paolo Bonzini
2022-02-18 23:59   ` Sean Christopherson
2022-02-23 16:23   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 12/18] KVM: x86/mmu: clear MMIO cache when unloading the MMU Paolo Bonzini
2022-02-18 23:59   ` Sean Christopherson
2022-02-23 16:32   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 13/18] KVM: x86: reset and reinitialize the MMU in __set_sregs_common Paolo Bonzini
2022-02-19  0:22   ` Sean Christopherson
2022-02-23 16:48   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 14/18] KVM: x86/mmu: avoid indirect call for get_cr3 Paolo Bonzini
2022-02-18 20:30   ` Sean Christopherson
2022-02-19 10:03     ` Paolo Bonzini
2022-02-24 11:02   ` Maxim Levitsky
2022-02-24 15:12     ` Sean Christopherson
2022-02-24 15:14       ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 15/18] KVM: x86/mmu: rename kvm_mmu_new_pgd, introduce variant that calls get_guest_pgd Paolo Bonzini
2022-02-18  9:39   ` Paolo Bonzini
2022-02-18 21:00     ` Sean Christopherson
2022-02-24 15:41       ` Maxim Levitsky
2022-02-25 17:40         ` Sean Christopherson
2022-02-17 21:03 ` [PATCH v2 16/18] KVM: x86: introduce KVM_REQ_MMU_UPDATE_ROOT Paolo Bonzini
2022-02-18 21:45   ` Sean Christopherson
2022-02-19  7:54     ` Paolo Bonzini
2022-02-22 16:06       ` Sean Christopherson
2022-02-24 15:50       ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 17/18] KVM: x86: flush TLB separately from MMU reset Paolo Bonzini
2022-02-18 23:57   ` Sean Christopherson
2022-02-21 15:01     ` Paolo Bonzini [this message]
2022-02-24 16:11   ` Maxim Levitsky
2022-02-17 21:03 ` [PATCH v2 18/18] KVM: x86: do not unload MMU roots on all role changes Paolo Bonzini
2022-02-24 16:25   ` Maxim Levitsky

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