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From: Ricardo Koller <ricarkol@google.com>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: pbonzini@redhat.com, maz@kernel.org, oupton@google.com,
	yuzenghui@huawei.com, dmatlack@google.com, kvm@vger.kernel.org,
	kvmarm@lists.linux.dev, qperret@google.com,
	catalin.marinas@arm.com, andrew.jones@linux.dev,
	seanjc@google.com, alexandru.elisei@arm.com,
	suzuki.poulose@arm.com, eric.auger@redhat.com, gshan@redhat.com,
	reijiw@google.com, rananta@google.com, bgardon@google.com,
	ricarkol@gmail.com
Subject: Re: [PATCH v5 12/12] KVM: arm64: Use local TLBI on permission relaxation
Date: Thu, 2 Mar 2023 11:06:37 -0800	[thread overview]
Message-ID: <ZADzvSK77CHBwcNN@google.com> (raw)
In-Reply-To: <6d407882-c34e-16f1-1662-2af588e982f7@arm.com>

Hi Vladimir,

On Thu, Mar 02, 2023 at 10:45:25AM +0000, Vladimir Murzin wrote:
> On 3/1/23 21:09, Ricardo Koller wrote:
> > Second, KVM does not set the VTTBR_EL2.CnP bit, so each
> > PE has its own TLB entry for the same page. KVM could tolerate that when
> > doing permission relaxation (i.e., not having changes broadcasted to all
> > PEs).
> 
> I'm might be missing something, but it seems that we do set CnP bit, at
> least in v6.2 we have
> 
> arch/arm64/include/asm/kvm_mmu.h
> 
> static __always_inline u64 kvm_get_vttbr(struct kvm_s2_mmu *mmu)
> {
>         struct kvm_vmid *vmid = &mmu->vmid;
>         u64 vmid_field, baddr;
>         u64 cnp = system_supports_cnp() ? VTTBR_CNP_BIT : 0;
> 
>         baddr = mmu->pgd_phys;
>         vmid_field = atomic64_read(&vmid->id) << VTTBR_VMID_SHIFT;
>         vmid_field &= VTTBR_VMID_MASK(kvm_arm_vmid_bits);
>         return kvm_phys_to_vttbr(baddr) | vmid_field | cnp;
> }
> 
> Cheers
> Vladimir

I need to fix the commit message. What I meant to say is that
this optimization is correct in the case where CnP is not set.

Thanks,
Ricardo

      reply	other threads:[~2023-03-02 19:06 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-01 21:09 [PATCH v5 00/12] Implement Eager Page Splitting for ARM Ricardo Koller
2023-03-01 21:09 ` [PATCH v5 01/12] KVM: arm64: Add KVM_PGTABLE_WALK ctx->flags for skipping BBM and CMO Ricardo Koller
2023-03-03  8:27   ` Shaoqin Huang
2023-03-01 21:09 ` [PATCH v5 02/12] KVM: arm64: Rename free_unlinked to free_removed Ricardo Koller
2023-03-03  8:31   ` Shaoqin Huang
2023-03-01 21:09 ` [PATCH v5 03/12] KVM: arm64: Add helper for creating unlinked stage2 subtrees Ricardo Koller
2023-03-03  9:02   ` Shaoqin Huang
2023-03-01 21:09 ` [PATCH v5 04/12] KVM: arm64: Add kvm_pgtable_stage2_split() Ricardo Koller
2023-03-03  9:09   ` Shaoqin Huang
2023-03-01 21:09 ` [PATCH v5 05/12] KVM: arm64: Refactor kvm_arch_commit_memory_region() Ricardo Koller
2023-03-03  9:14   ` Shaoqin Huang
2023-03-01 21:09 ` [PATCH v5 06/12] KVM: arm64: Add kvm_uninit_stage2_mmu() Ricardo Koller
2023-03-03  9:14   ` Shaoqin Huang
2023-03-01 21:09 ` [PATCH v5 07/12] KVM: arm64: Export kvm_are_all_memslots_empty() Ricardo Koller
2023-03-03  9:15   ` Shaoqin Huang
2023-03-01 21:09 ` [PATCH v5 08/12] KVM: arm64: Add KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE Ricardo Koller
2023-03-01 21:09 ` [PATCH v5 09/12] KVM: arm64: Split huge pages when dirty logging is enabled Ricardo Koller
2023-03-03  9:18   ` Shaoqin Huang
2023-03-01 21:09 ` [PATCH v5 10/12] KVM: arm64: Open-code kvm_mmu_write_protect_pt_masked() Ricardo Koller
2023-03-01 21:09 ` [PATCH v5 11/12] KVM: arm64: Split huge pages during KVM_CLEAR_DIRTY_LOG Ricardo Koller
2023-03-01 21:09 ` [PATCH v5 12/12] KVM: arm64: Use local TLBI on permission relaxation Ricardo Koller
2023-03-02 10:45   ` Vladimir Murzin
2023-03-02 19:06     ` Ricardo Koller [this message]

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