From: Sean Christopherson <seanjc@google.com>
To: David Matlack <dmatlack@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Marc Zyngier <maz@kernel.org>,
Huacai Chen <chenhuacai@kernel.org>,
leksandar Markovic <aleksandar.qemu.devel@gmail.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Peter Xu <peterx@redhat.com>, Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Peter Feiner <pfeiner@google.com>,
Andrew Jones <drjones@redhat.com>,
maciej.szmigiero@oracle.com, kvm@vger.kernel.org
Subject: Re: [PATCH 02/23] KVM: x86/mmu: Derive shadow MMU page role from parent
Date: Sat, 19 Feb 2022 01:14:16 +0000 [thread overview]
Message-ID: <YhBEaPWDoBiTpNV3@google.com> (raw)
In-Reply-To: <20220203010051.2813563-3-dmatlack@google.com>
On Thu, Feb 03, 2022, David Matlack wrote:
> Instead of computing the shadow page role from scratch for every new
> page, we can derive most of the information from the parent shadow page.
> This avoids redundant calculations such as the quadrant, and reduces the
Uh, calculating quadrant isn't redundant. The quadrant forces KVM to use different
(multiple) shadow pages to shadow a single guest PTE when the guest is using 32-bit
paging (1024 PTEs per page table vs. 512 PTEs per page table). The reason quadrant
is "quad" and not more or less is because 32-bit paging has two levels. First-level
PTEs can have quadrant=0/1, and that gets doubled for second-level PTEs because we
need to use four PTEs (two to handle 2x guest PTEs, and each of those needs to be
unique for the first-level PTEs they point at).
Indeed, this fails spectacularly when attempting to boot a 32-bit non-PAE kernel
with shadow paging enabled.
\��� ���\��� ��\���
P��\��`
BUG: unable to handle page fault for address: ff9fa81c
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
*pde = 00000000
����
Oops: 0000 [#1]��<���� SMP��<������<������<����
��<����CPU: 0 PID: 0 Comm: swapper ��<����G W 5.12.0 #10
��<����EIP: memblock_add_range.isra.18.constprop.23d�r
��<����Code: <83> 79 04 00 75 2c 83 38 01 75 06 83 78 08 00 74 02 0f 0b 89 11 8b
��<����EAX: c2af24bc EBX: fdffffff ECX: ff9fa818 EDX: 02000000
��<����ESI: 02000000 EDI: 00000000 EBP: c2909f30 ESP: c2909f0c
��<����DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00210006
��<����CR0: 80050033 CR2: ff9fa81c CR3: 02b76000 CR4: 00040600
��<����Call Trace:
��<���� ? printkd�r
��<���� ��<����memblock_reserved�r
��<���� ? 0xc2000000
��<���� ��<����setup_archd�r
��<���� ? vprintk_defaultd�r
��<���� ? vprintkd�r
��<���� ��<����start_kerneld�r
��<���� ��<����i386_start_kerneld�r
��<���� ��<����startup_32_smpd�r
����
CR2: 00000000ff9fa81c
��<����EIP: memblock_add_range.isra.18.constprop.23d�r
��<����Code: <83> 79 04 00 75 2c 83 38 01 75 06 83 78 08 00 74 02 0f 0b 89 11 8b
��<����EAX: c2af24bc EBX: fdffffff ECX: ff9fa818 EDX: 02000000
��<����ESI: 02000000 EDI: 00000000 EBP: c2909f30 ESP: c2909f0c
��<����DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00210006
��<����CR0: 80050033 CR2: ff9fa81c CR3: 02b76000 CR4: 00040600
> number of parameters to kvm_mmu_get_page().
>
> Preemptivel split out the role calculation to a separate function for
Preemptively.
> use in a following commit.
>
> No functional change intended.
>
> Signed-off-by: David Matlack <dmatlack@google.com>
> ---
next prev parent reply other threads:[~2022-02-19 1:14 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-03 1:00 [PATCH 00/23] Extend Eager Page Splitting to the shadow MMU David Matlack
2022-02-03 1:00 ` [PATCH 01/23] KVM: x86/mmu: Optimize MMU page cache lookup for all direct SPs David Matlack
2022-02-19 0:57 ` Sean Christopherson
2022-02-03 1:00 ` [PATCH 02/23] KVM: x86/mmu: Derive shadow MMU page role from parent David Matlack
2022-02-19 1:14 ` Sean Christopherson [this message]
2022-02-24 18:45 ` David Matlack
2022-03-04 0:22 ` David Matlack
2022-02-03 1:00 ` [PATCH 03/23] KVM: x86/mmu: Decompose kvm_mmu_get_page() into separate functions David Matlack
2022-02-19 1:25 ` Sean Christopherson
2022-02-24 18:54 ` David Matlack
2022-02-03 1:00 ` [PATCH 04/23] KVM: x86/mmu: Rename shadow MMU functions that deal with shadow pages David Matlack
2022-02-03 1:00 ` [PATCH 05/23] KVM: x86/mmu: Pass memslot to kvm_mmu_create_sp() David Matlack
2022-02-03 1:00 ` [PATCH 06/23] KVM: x86/mmu: Separate shadow MMU sp allocation from initialization David Matlack
2022-02-16 19:37 ` Ben Gardon
2022-02-16 21:42 ` David Matlack
2022-02-03 1:00 ` [PATCH 07/23] KVM: x86/mmu: Move huge page split sp allocation code to mmu.c David Matlack
2022-02-03 1:00 ` [PATCH 08/23] KVM: x86/mmu: Use common code to free kvm_mmu_page structs David Matlack
2022-02-03 1:00 ` [PATCH 09/23] KVM: x86/mmu: Use common code to allocate kvm_mmu_page structs from vCPU caches David Matlack
2022-02-03 1:00 ` [PATCH 10/23] KVM: x86/mmu: Pass const memslot to rmap_add() David Matlack
2022-02-23 23:25 ` Ben Gardon
2022-02-03 1:00 ` [PATCH 11/23] KVM: x86/mmu: Pass const memslot to kvm_mmu_init_sp() and descendants David Matlack
2022-02-23 23:27 ` Ben Gardon
2022-02-03 1:00 ` [PATCH 12/23] KVM: x86/mmu: Decouple rmap_add() and link_shadow_page() from kvm_vcpu David Matlack
2022-02-23 23:30 ` Ben Gardon
2022-02-03 1:00 ` [PATCH 13/23] KVM: x86/mmu: Update page stats in __rmap_add() David Matlack
2022-02-23 23:32 ` Ben Gardon
2022-02-23 23:35 ` Ben Gardon
2022-02-03 1:00 ` [PATCH 14/23] KVM: x86/mmu: Cache the access bits of shadowed translations David Matlack
2022-02-28 20:30 ` Ben Gardon
2022-02-03 1:00 ` [PATCH 15/23] KVM: x86/mmu: Pass access information to make_huge_page_split_spte() David Matlack
2022-02-28 20:32 ` Ben Gardon
2022-02-03 1:00 ` [PATCH 16/23] KVM: x86/mmu: Zap collapsible SPTEs at all levels in the shadow MMU David Matlack
2022-02-28 20:39 ` Ben Gardon
2022-03-03 19:42 ` David Matlack
2022-02-03 1:00 ` [PATCH 17/23] KVM: x86/mmu: Pass bool flush parameter to drop_large_spte() David Matlack
2022-02-28 20:47 ` Ben Gardon
2022-03-03 19:52 ` David Matlack
2022-02-03 1:00 ` [PATCH 18/23] KVM: x86/mmu: Extend Eager Page Splitting to the shadow MMU David Matlack
2022-02-28 21:09 ` Ben Gardon
2022-02-28 23:29 ` David Matlack
2022-02-03 1:00 ` [PATCH 19/23] KVM: Allow for different capacities in kvm_mmu_memory_cache structs David Matlack
2022-02-24 11:28 ` Marc Zyngier
2022-02-24 19:20 ` David Matlack
2022-03-04 21:59 ` David Matlack
2022-03-04 22:24 ` David Matlack
2022-03-05 16:55 ` Marc Zyngier
2022-03-07 23:49 ` David Matlack
2022-03-08 7:42 ` Marc Zyngier
2022-03-09 21:49 ` David Matlack
2022-03-10 8:30 ` Marc Zyngier
2022-02-03 1:00 ` [PATCH 20/23] KVM: Allow GFP flags to be passed when topping up MMU caches David Matlack
2022-02-28 21:12 ` Ben Gardon
2022-02-03 1:00 ` [PATCH 21/23] KVM: x86/mmu: Fully split huge pages that require extra pte_list_desc structs David Matlack
2022-02-28 21:22 ` Ben Gardon
2022-02-28 23:41 ` David Matlack
2022-03-01 0:37 ` Ben Gardon
2022-03-03 19:59 ` David Matlack
2022-02-03 1:00 ` [PATCH 22/23] KVM: x86/mmu: Split huge pages aliased by multiple SPTEs David Matlack
2022-02-03 1:00 ` [PATCH 23/23] KVM: selftests: Map x86_64 guest virtual memory with huge pages David Matlack
2022-03-07 5:21 ` [PATCH 00/23] Extend Eager Page Splitting to the shadow MMU Peter Xu
2022-03-07 23:39 ` David Matlack
2022-03-09 7:31 ` Peter Xu
2022-03-09 23:39 ` David Matlack
2022-03-10 7:03 ` Peter Xu
2022-03-10 19:26 ` David Matlack
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