From: Vishal Annapurve <vannapurve@google.com>
To: Sean Christopherson <seanjc@google.com>
Cc: David Hildenbrand <david@redhat.com>,
Ackerley Tng <ackerleytng@google.com>,
Fuad Tabba <tabba@google.com>,
kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-mm@kvack.org, pbonzini@redhat.com, chenhuacai@kernel.org,
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brauner@kernel.org, willy@infradead.org,
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jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com,
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mail@maciej.szmigiero.name, michael.roth@amd.com,
wei.w.wang@intel.com, liam.merwick@oracle.com,
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quic_pheragu@quicinc.com, catalin.marinas@arm.com,
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pankaj.gupta@amd.com
Subject: Re: [PATCH v8 06/13] KVM: x86: Generalize private fault lookups to guest_memfd fault lookups
Date: Mon, 5 May 2025 22:17:12 -0700 [thread overview]
Message-ID: <CAGtprH8DW-hqxbFdyo+Mg7MddsOAnN+rpLZUOHT-msD+OwCv=Q@mail.gmail.com> (raw)
In-Reply-To: <aBlCSGB86cp3B3zn@google.com>
On Mon, May 5, 2025 at 3:57 PM Sean Christopherson <seanjc@google.com> wrote:
> > ...
> > And not worry about lpage_infor for the time being, until we actually do
> > support larger pages.
>
> I don't want to completely punt on this, because if it gets messy, then I want
> to know now and have a solution in hand, not find out N months from now.
>
> That said, I don't expect it to be difficult. What we could punt on is
> performance of the lookups, which is the real reason KVM maintains the rather
> expensive disallow_lpage array.
>
> And that said, memslots can only bind to one guest_memfd instance, so I don't
> immediately see any reason why the guest_memfd ioctl() couldn't process the
> slots that are bound to it. I.e. why not update KVM_LPAGE_MIXED_FLAG from the
> guest_memfd ioctl() instead of from KVM_SET_MEMORY_ATTRIBUTES?
I am missing the point here to update KVM_LPAGE_MIXED_FLAG for the
scenarios where in-place memory conversion will be supported with
guest_memfd. As guest_memfd support for hugepages comes with the
design that hugepages can't have mixed attributes. i.e. max_order
returned by get_pfn will always have the same attributes for the folio
range.
Is your suggestion around using guest_memfd ioctl() to also toggle
memory attributes for the scenarios where guest_memfd instance doesn't
have in-place memory conversion feature enabled?
next prev parent reply other threads:[~2025-05-06 5:17 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-30 16:56 [PATCH v8 00/13] KVM: Mapping guest_memfd backed memory at the host for software protected VMs Fuad Tabba
2025-04-30 16:56 ` [PATCH v8 01/13] KVM: Rename CONFIG_KVM_PRIVATE_MEM to CONFIG_KVM_GMEM Fuad Tabba
2025-05-01 17:38 ` Ira Weiny
2025-04-30 16:56 ` [PATCH v8 02/13] KVM: Rename CONFIG_KVM_GENERIC_PRIVATE_MEM to CONFIG_KVM_GENERIC_GMEM_POPULATE Fuad Tabba
2025-05-01 18:10 ` Ira Weiny
2025-05-02 6:44 ` David Hildenbrand
2025-05-02 14:24 ` Ira Weiny
2025-04-30 16:56 ` [PATCH v8 03/13] KVM: Rename kvm_arch_has_private_mem() to kvm_arch_supports_gmem() Fuad Tabba
2025-05-01 18:18 ` Ira Weiny
2025-04-30 16:56 ` [PATCH v8 04/13] KVM: x86: Rename kvm->arch.has_private_mem to kvm->arch.supports_gmem Fuad Tabba
2025-05-01 18:19 ` Ira Weiny
2025-04-30 16:56 ` [PATCH v8 05/13] KVM: Rename kvm_slot_can_be_private() to kvm_slot_has_gmem() Fuad Tabba
2025-05-01 21:37 ` Ira Weiny
2025-04-30 16:56 ` [PATCH v8 06/13] KVM: x86: Generalize private fault lookups to guest_memfd fault lookups Fuad Tabba
2025-04-30 18:58 ` Ackerley Tng
2025-05-01 9:53 ` Fuad Tabba
2025-05-02 15:04 ` David Hildenbrand
2025-05-02 16:21 ` Sean Christopherson
2025-05-02 22:00 ` Ackerley Tng
2025-05-05 8:01 ` David Hildenbrand
2025-05-05 22:57 ` Sean Christopherson
2025-05-06 5:17 ` Vishal Annapurve [this message]
2025-05-06 5:28 ` Vishal Annapurve
2025-05-06 13:58 ` Sean Christopherson
2025-05-06 14:15 ` David Hildenbrand
2025-05-06 20:46 ` Ackerley Tng
2025-05-08 14:12 ` Sean Christopherson
2025-05-08 14:46 ` David Hildenbrand
2025-05-09 21:04 ` James Houghton
2025-05-09 22:29 ` David Hildenbrand
2025-05-09 22:38 ` James Houghton
2025-05-06 19:27 ` Ackerley Tng
2025-05-05 23:09 ` Ackerley Tng
2025-05-05 23:17 ` Sean Christopherson
2025-05-01 21:38 ` Ira Weiny
2025-04-30 16:56 ` [PATCH v8 07/13] KVM: Fix comments that refer to slots_lock Fuad Tabba
2025-04-30 21:30 ` David Hildenbrand
2025-05-01 21:43 ` Ira Weiny
2025-05-02 12:07 ` Fuad Tabba
2025-04-30 16:56 ` [PATCH v8 08/13] KVM: guest_memfd: Allow host to map guest_memfd() pages Fuad Tabba
2025-04-30 21:33 ` David Hildenbrand
2025-05-01 8:07 ` Fuad Tabba
2025-05-02 15:11 ` David Hildenbrand
2025-05-02 22:06 ` Ackerley Tng
2025-05-02 22:29 ` Ackerley Tng
2025-05-06 8:47 ` Yan Zhao
2025-05-05 21:06 ` Ira Weiny
2025-05-06 12:15 ` Fuad Tabba
2025-05-09 20:54 ` James Houghton
2025-05-11 8:03 ` David Hildenbrand
2025-05-12 7:08 ` Fuad Tabba
2025-05-12 19:29 ` James Houghton
2025-05-12 7:46 ` Roy, Patrick
2025-04-30 16:56 ` [PATCH v8 09/13] KVM: arm64: Refactor user_mem_abort() calculation of force_pte Fuad Tabba
2025-04-30 21:35 ` David Hildenbrand
2025-04-30 16:56 ` [PATCH v8 10/13] KVM: arm64: Handle guest_memfd()-backed guest page faults Fuad Tabba
2025-05-09 20:15 ` James Houghton
2025-05-12 7:07 ` Fuad Tabba
2025-04-30 16:56 ` [PATCH v8 11/13] KVM: arm64: Enable mapping guest_memfd in arm64 Fuad Tabba
2025-05-09 21:08 ` James Houghton
2025-05-12 6:55 ` Fuad Tabba
2025-04-30 16:56 ` [PATCH v8 12/13] KVM: x86: KVM_X86_SW_PROTECTED_VM to support guest_memfd shared memory Fuad Tabba
2025-04-30 16:56 ` [PATCH v8 13/13] KVM: guest_memfd: selftests: guest_memfd mmap() test when mapping is allowed Fuad Tabba
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