From: David Stevens <stevensd@chromium.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Yu Zhang <yu.c.zhang@linux.intel.com>,
Isaku Yamahata <isaku.yamahata@gmail.com>,
Zhi Wang <zhi.wang.linux@gmail.com>,
kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, David Stevens <stevensd@chromium.org>
Subject: [PATCH v9 0/6] KVM: allow mapping non-refcounted pages
Date: Mon, 11 Sep 2023 11:16:30 +0900 [thread overview]
Message-ID: <20230911021637.1941096-1-stevensd@google.com> (raw)
From: David Stevens <stevensd@chromium.org>
This patch series adds support for mapping VM_IO and VM_PFNMAP memory
that is backed by struct pages that aren't currently being refcounted
(e.g. tail pages of non-compound higher order allocations) into the
guest.
Our use case is virtio-gpu blob resources [1], which directly map host
graphics buffers into the guest as "vram" for the virtio-gpu device.
This feature currently does not work on systems using the amdgpu driver,
as that driver allocates non-compound higher order pages via
ttm_pool_alloc_page.
First, this series replaces the __gfn_to_pfn_memslot API with a more
extensible __kvm_faultin_pfn API. The updated API rearranges
__gfn_to_pfn_memslot's args into a struct and where possible packs the
bool arguments into a FOLL_ flags argument. The refactoring changes do
not change any behavior.
From there, this series extends the __kvm_faultin_pfn API so that
non-refconuted pages can be safely handled. This invloves adding an
input parameter to indicate whether the caller can safely use
non-refcounted pfns and an output parameter to tell the caller whether
or not the returned page is refcounted. This change includes a breaking
change, by disallowing non-refcounted pfn mappings by default, as such
mappings are unsafe. To allow such systems to continue to function, an
opt-in module parameter is added to allow the unsafe behavior.
This series only adds support for non-refcounted pages to x86. Other
MMUs can likely be updated without too much difficulty, but it is not
needed at this point. Updating other parts of KVM (e.g. pfncache) is not
straightforward [2].
[1]
https://patchwork.kernel.org/project/dri-devel/cover/20200814024000.2485-1-gurchetansingh@chromium.org/
[2] https://lore.kernel.org/all/ZBEEQtmtNPaEqU1i@google.com/
v8 -> v9:
- Make paying attention to is_refcounted_page mandatory. This means
that FOLL_GET is no longer necessary. For compatibility with
un-migrated callers, add a temporary parameter to sidestep
ref-counting issues.
- Add allow_unsafe_mappings, which is a breaking change.
- Migrate kvm_vcpu_map and other callsites used by x86 to the new API.
- Drop arm and ppc changes.
v7 -> v8:
- Set access bits before releasing mmu_lock.
- Pass FOLL_GET on 32-bit x86 or !tdp_enabled.
- Refactor FOLL_GET handling, add kvm_follow_refcounted_pfn helper.
- Set refcounted bit on >4k pages.
- Add comments and apply formatting suggestions.
- rebase on kvm next branch.
v6 -> v7:
- Replace __gfn_to_pfn_memslot with a more flexible __kvm_faultin_pfn,
and extend that API to support non-refcounted pages (complete
rewrite).
David Stevens (5):
KVM: mmu: Introduce __kvm_follow_pfn function
KVM: mmu: Improve handling of non-refcounted pfns
KVM: Migrate kvm_vcpu_map to __kvm_follow_pfn
KVM: x86: Migrate to __kvm_follow_pfn
KVM: x86/mmu: Handle non-refcounted pages
Sean Christopherson (1):
KVM: Assert that a page's refcount is elevated when marking
accessed/dirty
arch/x86/kvm/mmu/mmu.c | 93 +++++++---
arch/x86/kvm/mmu/mmu_internal.h | 1 +
arch/x86/kvm/mmu/paging_tmpl.h | 8 +-
arch/x86/kvm/mmu/spte.c | 4 +-
arch/x86/kvm/mmu/spte.h | 12 +-
arch/x86/kvm/mmu/tdp_mmu.c | 22 ++-
arch/x86/kvm/x86.c | 12 +-
include/linux/kvm_host.h | 42 ++++-
virt/kvm/kvm_main.c | 294 +++++++++++++++++++-------------
virt/kvm/kvm_mm.h | 3 +-
virt/kvm/pfncache.c | 11 +-
11 files changed, 339 insertions(+), 163 deletions(-)
--
2.42.0.283.g2d96d420d3-goog
next reply other threads:[~2023-09-11 2:16 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-11 2:16 David Stevens [this message]
2023-09-11 2:16 ` [PATCH v9 1/6] KVM: Assert that a page's refcount is elevated when marking accessed/dirty David Stevens
2023-09-11 2:16 ` [PATCH v9 2/6] KVM: mmu: Introduce __kvm_follow_pfn function David Stevens
2023-10-03 16:54 ` Maxim Levitsky
2024-02-06 1:25 ` Sean Christopherson
2024-02-06 3:16 ` Sean Christopherson
2024-02-13 3:27 ` Sean Christopherson
2024-02-13 3:44 ` Sean Christopherson
2023-09-11 2:16 ` [PATCH v9 3/6] KVM: mmu: Improve handling of non-refcounted pfns David Stevens
2023-10-03 16:54 ` Maxim Levitsky
2024-02-06 2:54 ` Sean Christopherson
2024-02-13 3:44 ` Sean Christopherson
2023-09-11 2:16 ` [PATCH v9 4/6] KVM: Migrate kvm_vcpu_map to __kvm_follow_pfn David Stevens
2023-10-03 16:54 ` Maxim Levitsky
2023-09-11 2:16 ` [PATCH v9 5/6] KVM: x86: Migrate " David Stevens
2023-10-03 16:54 ` Maxim Levitsky
2023-10-03 20:58 ` Sean Christopherson
2023-09-11 2:16 ` [PATCH v9 6/6] KVM: x86/mmu: Handle non-refcounted pages David Stevens
2023-09-18 9:53 ` Dmitry Osipenko
2023-09-19 2:25 ` David Stevens
2023-09-30 13:34 ` Dmitry Osipenko
2023-09-18 9:58 ` Dmitry Osipenko
2023-09-18 11:19 ` Dmitry Osipenko
2023-09-19 2:59 ` David Stevens
2023-09-21 20:06 ` Dmitry Osipenko
2023-09-30 13:34 ` Dmitry Osipenko
2023-09-19 2:31 ` David Stevens
2023-09-21 20:04 ` Dmitry Osipenko
2024-02-06 3:02 ` Sean Christopherson
2023-10-03 16:54 ` Maxim Levitsky
2024-02-06 3:23 ` Sean Christopherson
2023-09-29 5:19 ` [PATCH v9 0/6] KVM: allow mapping " Christoph Hellwig
2023-09-29 16:06 ` Sean Christopherson
2023-10-02 6:25 ` Christoph Hellwig
2024-02-06 3:29 ` Sean Christopherson
2023-10-31 4:30 ` David Stevens
2023-10-31 14:30 ` Sean Christopherson
2023-12-12 1:59 ` David Stevens
2023-12-20 1:37 ` Sean Christopherson
2024-02-06 3:30 ` Sean Christopherson
2024-02-13 3:39 ` Sean Christopherson
2024-02-21 6:05 ` David Stevens
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