From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, dmatlack@google.com
Subject: Re: [PATCH v2 10/25] KVM: x86/mmu: remove ept_ad field
Date: Tue, 8 Mar 2022 17:42:45 +0000 [thread overview]
Message-ID: <YieVlbIwYIIbEmd7@google.com> (raw)
In-Reply-To: <20220221162243.683208-11-pbonzini@redhat.com>
On Mon, Feb 21, 2022, Paolo Bonzini wrote:
> The ept_ad field is used during page walk to determine if the guest PTEs
> have accessed and dirty bits. In the MMU role, the ad_disabled
> bit represents whether the *shadow* PTEs have the bits, so it
> would be incorrect to replace PT_HAVE_ACCESSED_DIRTY with just
> !mmu->mmu_role.base.ad_disabled.
>
> However, the similar field in the CPU mode, ad_disabled, is initialized
> correctly: to the opposite value of ept_ad for shadow EPT, and zero
> for non-EPT guest paging modes (which always have A/D bits). It is
> therefore possible to compute PT_HAVE_ACCESSED_DIRTY from the CPU mode,
> like other page-format fields; it just has to be inverted to account
> for the different polarity.
>
> Having a CPU mode that is distinct from the MMU roles in fact would even
> allow to remove PT_HAVE_ACCESSED_DIRTY macro altogether, and always use
> !mmu->cpu_mode.base.ad_disabled. I am not doing this because the macro
> has a small effect in terms of dead code elimination:
>
> text data bss dec hex
> 103544 16665 112 120321 1d601 # as of this patch
> 103746 16665 112 120523 1d6cb # without PT_HAVE_ACCESSED_DIRTY
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
Reviewed-by: Sean Christopherson <seanjc@google.com>
next prev parent reply other threads:[~2022-03-08 17:42 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-21 16:22 [PATCH v2 00/25] KVM MMU refactoring part 2: role changes Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 01/25] KVM: x86/mmu: avoid indirect call for get_cr3 Paolo Bonzini
2022-03-08 16:16 ` Sean Christopherson
2022-03-08 16:21 ` Paolo Bonzini
2022-03-08 16:32 ` Sean Christopherson
2022-03-08 16:43 ` Paolo Bonzini
2022-03-08 16:53 ` Sean Christopherson
2022-03-08 17:14 ` Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 02/25] KVM: x86/mmu: nested EPT cannot be used in SMM Paolo Bonzini
2022-03-08 16:18 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 03/25] KVM: x86/mmu: constify uses of struct kvm_mmu_role_regs Paolo Bonzini
2022-03-08 16:22 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 04/25] KVM: x86/mmu: pull computation of kvm_mmu_role_regs to kvm_init_mmu Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 05/25] KVM: x86/mmu: rephrase unclear comment Paolo Bonzini
2022-03-08 16:39 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 06/25] KVM: nVMX/nSVM: do not monkey-patch inject_page_fault callback Paolo Bonzini
2022-03-08 17:13 ` Sean Christopherson
2022-03-08 20:34 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 07/25] KVM: x86/mmu: remove "bool base_only" arguments Paolo Bonzini
2022-03-08 17:15 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 08/25] KVM: x86/mmu: split cpu_mode from mmu_role Paolo Bonzini
2022-03-08 17:36 ` Sean Christopherson
2022-03-08 17:49 ` Paolo Bonzini
2022-03-08 18:55 ` Sean Christopherson
2022-03-09 9:58 ` Paolo Bonzini
2022-03-09 15:38 ` Sean Christopherson
2022-03-09 15:40 ` Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 09/25] KVM: x86/mmu: do not recompute root level from kvm_mmu_role_regs Paolo Bonzini
2022-03-08 17:41 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 10/25] KVM: x86/mmu: remove ept_ad field Paolo Bonzini
2022-03-08 17:42 ` Sean Christopherson [this message]
2022-02-21 16:22 ` [PATCH v2 11/25] KVM: x86/mmu: remove kvm_calc_shadow_root_page_role_common Paolo Bonzini
2022-03-08 17:48 ` Sean Christopherson
2022-03-08 17:50 ` Paolo Bonzini
2022-03-08 18:17 ` Sean Christopherson
2022-03-08 18:18 ` Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 12/25] KVM: x86/mmu: cleanup computation of MMU roles for two-dimensional paging Paolo Bonzini
2022-03-08 18:11 ` Sean Christopherson
2022-03-08 18:24 ` Paolo Bonzini
2022-03-08 18:44 ` Sean Christopherson
2022-03-08 18:38 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 13/25] KVM: x86/mmu: cleanup computation of MMU roles for shadow paging Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 14/25] KVM: x86/mmu: store shadow EFER.NX in the MMU role Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 15/25] KVM: x86/mmu: remove extended bits from mmu_role, rename field Paolo Bonzini
2022-03-08 19:02 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 16/25] KVM: x86/mmu: rename kvm_mmu_role union Paolo Bonzini
2022-03-08 19:15 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 17/25] KVM: x86/mmu: remove redundant bits from extended role Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 18/25] KVM: x86/mmu: remove valid " Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 19/25] KVM: x86/mmu: simplify and/or inline computation of shadow MMU roles Paolo Bonzini
2022-03-08 19:35 ` Sean Christopherson
2022-03-08 19:41 ` Sean Christopherson
2022-03-09 10:33 ` Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 20/25] KVM: x86/mmu: pull CPU mode computation to kvm_init_mmu Paolo Bonzini
2022-03-08 19:45 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 21/25] KVM: x86/mmu: replace shadow_root_level with root_role.level Paolo Bonzini
2022-03-08 19:48 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 22/25] KVM: x86/mmu: replace root_level with cpu_mode.base.level Paolo Bonzini
2022-03-08 19:49 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 23/25] KVM: x86/mmu: replace direct_map with root_role.direct Paolo Bonzini
2022-03-08 19:52 ` Sean Christopherson
2022-02-21 16:22 ` [PATCH v2 24/25] KVM: x86/mmu: initialize constant-value fields just once Paolo Bonzini
2022-03-08 20:58 ` Sean Christopherson
2022-03-09 10:34 ` Paolo Bonzini
2022-02-21 16:22 ` [PATCH v2 25/25] KVM: x86/mmu: extract initialization of the page walking data Paolo Bonzini
2022-03-08 20:02 ` Sean Christopherson
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