From: Sean Christopherson <seanjc@google.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: David Matlack <dmatlack@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Marc Zyngier <maz@kernel.org>,
Huacai Chen <chenhuacai@kernel.org>,
Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
Anup Patel <anup@brainfault.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Andrew Jones <drjones@redhat.com>,
Ben Gardon <bgardon@google.com>, Peter Xu <peterx@redhat.com>,
"Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>,
"moderated list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)"
<kvmarm@lists.cs.columbia.edu>,
"open list:KERNEL VIRTUAL MACHINE FOR MIPS (KVM/mips)"
<linux-mips@vger.kernel.org>,
"open list:KERNEL VIRTUAL MACHINE FOR MIPS (KVM/mips)"
<kvm@vger.kernel.org>,
"open list:KERNEL VIRTUAL MACHINE FOR RISC-V (KVM/riscv)"
<kvm-riscv@lists.infradead.org>,
Peter Feiner <pfeiner@google.com>
Subject: Re: [PATCH v4 03/20] KVM: x86/mmu: Derive shadow MMU page role from parent
Date: Tue, 10 May 2022 13:31:21 +0000 [thread overview]
Message-ID: <YnppKY8j78Z1E6bH@google.com> (raw)
In-Reply-To: <CAJhGHyDQn=atFmn5o2TREW9cSY5Tv1F1vsSekzor6uYQxDgcfQ@mail.gmail.com>
On Tue, May 10, 2022, Lai Jiangshan wrote:
> ()
>
> On Tue, May 10, 2022 at 5:04 AM David Matlack <dmatlack@google.com> wrote:
> >
> > On Sat, May 7, 2022 at 1:28 AM Lai Jiangshan <jiangshanlai@gmail.com> wrote:
> > > > +static union kvm_mmu_page_role kvm_mmu_child_role(u64 *sptep, bool direct, u32 access)
> > > > +{
> > > > + struct kvm_mmu_page *parent_sp = sptep_to_sp(sptep);
> > > > + union kvm_mmu_page_role role;
> > > > +
> > > > + role = parent_sp->role;
> > > > + role.level--;
> > > > + role.access = access;
> > > > + role.direct = direct;
> > > > +
> > > > + /*
> > > > + * If the guest has 4-byte PTEs then that means it's using 32-bit,
> > > > + * 2-level, non-PAE paging. KVM shadows such guests using 4 PAE page
> > > > + * directories, each mapping 1/4 of the guest's linear address space
> > > > + * (1GiB). The shadow pages for those 4 page directories are
> > > > + * pre-allocated and assigned a separate quadrant in their role.
> > >
> > >
> > > It is not going to be true in patchset:
> > > [PATCH V2 0/7] KVM: X86/MMU: Use one-off special shadow page for special roots
> > >
> > > https://lore.kernel.org/lkml/20220503150735.32723-1-jiangshanlai@gmail.com/
> > >
> > > The shadow pages for those 4 page directories are also allocated on demand.
> >
> > Ack. I can even just drop this sentence in v5, it's just background information.
>
> No, if one-off special shadow pages are used.
>
> kvm_mmu_child_role() should be:
>
> + if (role.has_4_byte_gpte) {
> + if (role.level == PG_LEVEL_4K)
> + role.quadrant = (sptep - parent_sp->spt) % 2;
> + if (role.level == PG_LEVEL_2M)
If the code ends up looking anything like this, please use PT32_ROOT_LEVEL instead
of PG_LEVEL_2M. PSE paging has 4M huge pages, using PG_LEVEL_2M is confusing.
Or even better might be to do:
if (role.level == PG_LEVEL_4k)
...
else
...
Or arithmetic using role.level directly, a la the current code.
next prev parent reply other threads:[~2022-05-10 13:50 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-22 21:05 [PATCH v4 00/20] KVM: Extend Eager Page Splitting to the shadow MMU David Matlack
2022-04-22 21:05 ` [PATCH v4 01/20] KVM: x86/mmu: Optimize MMU page cache lookup for all direct SPs David Matlack
2022-05-07 7:46 ` Lai Jiangshan
2022-04-22 21:05 ` [PATCH v4 02/20] KVM: x86/mmu: Use a bool for direct David Matlack
2022-05-07 7:46 ` Lai Jiangshan
2022-04-22 21:05 ` [PATCH v4 03/20] KVM: x86/mmu: Derive shadow MMU page role from parent David Matlack
2022-05-05 21:50 ` Sean Christopherson
2022-05-09 22:10 ` David Matlack
2022-05-10 2:38 ` Lai Jiangshan
2022-05-07 8:28 ` Lai Jiangshan
2022-05-09 21:04 ` David Matlack
2022-05-10 2:58 ` Lai Jiangshan
2022-05-10 13:31 ` Sean Christopherson [this message]
2022-05-12 16:10 ` David Matlack
2022-05-13 18:26 ` David Matlack
2022-04-22 21:05 ` [PATCH v4 04/20] KVM: x86/mmu: Decompose kvm_mmu_get_page() into separate functions David Matlack
2022-05-05 21:58 ` Sean Christopherson
2022-04-22 21:05 ` [PATCH v4 05/20] KVM: x86/mmu: Consolidate shadow page allocation and initialization David Matlack
2022-05-05 22:10 ` Sean Christopherson
2022-05-09 20:53 ` David Matlack
2022-04-22 21:05 ` [PATCH v4 06/20] KVM: x86/mmu: Rename shadow MMU functions that deal with shadow pages David Matlack
2022-05-05 22:15 ` Sean Christopherson
2022-04-22 21:05 ` [PATCH v4 07/20] KVM: x86/mmu: Move guest PT write-protection to account_shadowed() David Matlack
2022-05-05 22:51 ` Sean Christopherson
2022-05-09 21:18 ` David Matlack
2022-04-22 21:05 ` [PATCH v4 08/20] KVM: x86/mmu: Pass memory caches to allocate SPs separately David Matlack
2022-05-05 23:00 ` Sean Christopherson
2022-04-22 21:05 ` [PATCH v4 09/20] KVM: x86/mmu: Replace vcpu with kvm in kvm_mmu_alloc_shadow_page() David Matlack
2022-04-22 21:05 ` [PATCH v4 10/20] KVM: x86/mmu: Pass kvm pointer separately from vcpu to kvm_mmu_find_shadow_page() David Matlack
2022-04-22 21:05 ` [PATCH v4 11/20] KVM: x86/mmu: Allow for NULL vcpu pointer in __kvm_mmu_get_shadow_page() David Matlack
2022-05-05 23:33 ` Sean Christopherson
2022-05-09 21:26 ` David Matlack
2022-05-09 22:56 ` Sean Christopherson
2022-05-09 23:59 ` David Matlack
2022-04-22 21:05 ` [PATCH v4 12/20] KVM: x86/mmu: Pass const memslot to rmap_add() David Matlack
2022-04-22 21:05 ` [PATCH v4 13/20] KVM: x86/mmu: Decouple rmap_add() and link_shadow_page() from kvm_vcpu David Matlack
2022-05-05 23:46 ` Sean Christopherson
2022-05-09 21:27 ` David Matlack
2022-04-22 21:05 ` [PATCH v4 14/20] KVM: x86/mmu: Update page stats in __rmap_add() David Matlack
2022-04-22 21:05 ` [PATCH v4 15/20] KVM: x86/mmu: Cache the access bits of shadowed translations David Matlack
2022-05-06 19:47 ` Sean Christopherson
2022-05-09 16:10 ` Sean Christopherson
2022-05-09 21:29 ` David Matlack
2022-04-22 21:05 ` [PATCH v4 16/20] KVM: x86/mmu: Extend make_huge_page_split_spte() for the shadow MMU David Matlack
2022-05-09 16:22 ` Sean Christopherson
2022-05-09 21:31 ` David Matlack
2022-04-22 21:05 ` [PATCH v4 17/20] KVM: x86/mmu: Zap collapsible SPTEs at all levels in " David Matlack
2022-05-09 16:31 ` Sean Christopherson
2022-05-09 21:34 ` David Matlack
2022-04-22 21:05 ` [PATCH v4 18/20] KVM: x86/mmu: Refactor drop_large_spte() David Matlack
2022-05-09 16:36 ` Sean Christopherson
2022-04-22 21:05 ` [PATCH v4 19/20] KVM: Allow for different capacities in kvm_mmu_memory_cache structs David Matlack
2022-04-22 21:05 ` [PATCH v4 20/20] KVM: x86/mmu: Extend Eager Page Splitting to nested MMUs David Matlack
2022-05-07 7:51 ` Lai Jiangshan
2022-05-09 21:40 ` David Matlack
2022-05-09 16:48 ` Sean Christopherson
2022-05-09 21:44 ` David Matlack
2022-05-09 22:47 ` Sean Christopherson
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