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From: Peter Xu <peterx@redhat.com>
To: David Matlack <dmatlack@google.com>
Cc: Marc Zyngier <maz@kernel.org>, Albert Ou <aou@eecs.berkeley.edu>,
	"open list:KERNEL VIRTUAL MACHINE FOR MIPS \(KVM/mips\)"
	<kvm@vger.kernel.org>, Huacai Chen <chenhuacai@kernel.org>,
	"open list:KERNEL VIRTUAL MACHINE FOR MIPS \(KVM/mips\)"
	<linux-mips@vger.kernel.org>,
	Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	"open list:KERNEL VIRTUAL MACHINE FOR RISC-V \(KVM/riscv\)"
	<kvm-riscv@lists.infradead.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Ben Gardon <bgardon@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	maciej.szmigiero@oracle.com,
	"moderated list:KERNEL VIRTUAL MACHINE FOR ARM64 \(KVM/arm64\)"
	<kvmarm@lists.cs.columbia.edu>, Peter Feiner <pfeiner@google.com>
Subject: Re: [PATCH v2 08/26] KVM: x86/mmu: Link spt to sp during allocation
Date: Tue, 15 Mar 2022 18:04:11 +0800	[thread overview]
Message-ID: <YjBkm8mYKNc5sdpU@xz-m1.local> (raw)
In-Reply-To: <20220311002528.2230172-9-dmatlack@google.com>

On Fri, Mar 11, 2022 at 12:25:10AM +0000, David Matlack wrote:
> Link the shadow page table to the sp (via set_page_private()) during
> allocation rather than initialization. This is a more logical place to
> do it because allocation time is also where we do the reverse link
> (setting sp->spt).
> 
> This creates one extra call to set_page_private(), but having multiple
> calls to set_page_private() is unavoidable anyway. We either do
> set_page_private() during allocation, which requires 1 per allocation
> function, or we do it during initialization, which requires 1 per
> initialization function.
> 
> No functional change intended.
> 
> Suggested-by: Ben Gardon <bgardon@google.com>
> Signed-off-by: David Matlack <dmatlack@google.com>

Ah I should have read one more patch before commenting in previous one..

Personally I (a little bit) like the other way around, since if with this
in mind ideally we should also keep the use_mmu_page accounting in
allocation helper:

  kvm_mod_used_mmu_pages(vcpu->kvm, 1);

But then we dup yet another line to all elsewheres as long as sp allocated.

IOW, in my opinion the helpers should service 1st on code deduplications
rather than else.  No strong opinion though..

Thanks,

-- 
Peter Xu

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  reply	other threads:[~2022-03-15 10:04 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-11  0:25 [PATCH v2 00/26] Extend Eager Page Splitting to the shadow MMU David Matlack
2022-03-11  0:25 ` [PATCH v2 01/26] KVM: x86/mmu: Optimize MMU page cache lookup for all direct SPs David Matlack
2022-03-15  7:40   ` Peter Xu
2022-03-22 18:16     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 02/26] KVM: x86/mmu: Use a bool for direct David Matlack
2022-03-15  7:46   ` Peter Xu
2022-03-22 18:21     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 03/26] KVM: x86/mmu: Derive shadow MMU page role from parent David Matlack
2022-03-15  8:15   ` Peter Xu
2022-03-22 18:30     ` David Matlack
2022-03-30 14:25       ` Peter Xu
2022-03-11  0:25 ` [PATCH v2 04/26] KVM: x86/mmu: Decompose kvm_mmu_get_page() into separate functions David Matlack
2022-03-15  8:50   ` Peter Xu
2022-03-22 22:09     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 05/26] KVM: x86/mmu: Rename shadow MMU functions that deal with shadow pages David Matlack
2022-03-15  8:52   ` Peter Xu
2022-03-22 21:35     ` David Matlack
2022-03-30 14:28       ` Peter Xu
2022-03-11  0:25 ` [PATCH v2 06/26] KVM: x86/mmu: Pass memslot to kvm_mmu_new_shadow_page() David Matlack
2022-03-15  9:03   ` Peter Xu
2022-03-22 22:05     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 07/26] KVM: x86/mmu: Separate shadow MMU sp allocation from initialization David Matlack
2022-03-15  9:54   ` Peter Xu
2022-03-11  0:25 ` [PATCH v2 08/26] KVM: x86/mmu: Link spt to sp during allocation David Matlack
2022-03-15 10:04   ` Peter Xu [this message]
2022-03-22 22:30     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 09/26] KVM: x86/mmu: Move huge page split sp allocation code to mmu.c David Matlack
2022-03-15 10:17   ` Peter Xu
2022-03-11  0:25 ` [PATCH v2 10/26] KVM: x86/mmu: Use common code to free kvm_mmu_page structs David Matlack
2022-03-15 10:22   ` Peter Xu
2022-03-22 22:33     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 11/26] KVM: x86/mmu: Use common code to allocate kvm_mmu_page structs from vCPU caches David Matlack
2022-03-15 10:27   ` Peter Xu
2022-03-22 22:35     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 12/26] KVM: x86/mmu: Pass const memslot to rmap_add() David Matlack
2022-03-11  0:25 ` [PATCH v2 13/26] KVM: x86/mmu: Pass const memslot to init_shadow_page() and descendants David Matlack
2022-03-11  0:25 ` [PATCH v2 14/26] KVM: x86/mmu: Decouple rmap_add() and link_shadow_page() from kvm_vcpu David Matlack
2022-03-15 10:37   ` Peter Xu
2022-03-11  0:25 ` [PATCH v2 15/26] KVM: x86/mmu: Update page stats in __rmap_add() David Matlack
2022-03-15 10:39   ` Peter Xu
2022-03-11  0:25 ` [PATCH v2 16/26] KVM: x86/mmu: Cache the access bits of shadowed translations David Matlack
2022-03-16  8:32   ` Peter Xu
2022-03-22 22:51     ` David Matlack
2022-03-30 18:30       ` Peter Xu
2022-03-31 21:40         ` David Matlack
2022-03-11  0:25 ` [PATCH v2 17/26] KVM: x86/mmu: Pass access information to make_huge_page_split_spte() David Matlack
2022-03-16  8:44   ` Peter Xu
2022-03-22 23:08     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 18/26] KVM: x86/mmu: Zap collapsible SPTEs at all levels in the shadow MMU David Matlack
2022-03-16  8:49   ` Peter Xu
2022-03-22 23:11     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 19/26] KVM: x86/mmu: Refactor drop_large_spte() David Matlack
2022-03-16  8:53   ` Peter Xu
2022-03-11  0:25 ` [PATCH v2 20/26] KVM: x86/mmu: Extend Eager Page Splitting to the shadow MMU David Matlack
2022-03-16 10:26   ` Peter Xu
2022-03-22  0:07     ` David Matlack
2022-03-22 23:58     ` David Matlack
2022-03-30 18:34       ` Peter Xu
2022-03-31 19:57         ` David Matlack
2022-03-11  0:25 ` [PATCH v2 21/26] KVM: Allow for different capacities in kvm_mmu_memory_cache structs David Matlack
2022-03-19  5:27   ` Anup Patel
2022-03-22 23:13     ` David Matlack
2022-03-11  0:25 ` [PATCH v2 22/26] KVM: Allow GFP flags to be passed when topping up MMU caches David Matlack
2022-03-11  0:25 ` [PATCH v2 23/26] KVM: x86/mmu: Fully split huge pages that require extra pte_list_desc structs David Matlack
2022-03-11  0:25 ` [PATCH v2 24/26] KVM: x86/mmu: Split huge pages aliased by multiple SPTEs David Matlack
2022-03-11  0:25 ` [PATCH v2 25/26] KVM: x86/mmu: Drop NULL pte_list_desc_cache fallback David Matlack
2022-03-11  0:25 ` [PATCH v2 26/26] KVM: selftests: Map x86_64 guest virtual memory with huge pages David Matlack

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