From: Sean Christopherson <seanjc@google.com>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: Anish Moorthy <amoorthy@google.com>, Peter Xu <peterx@redhat.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
maz@kernel.org, oliver.upton@linux.dev,
James Houghton <jthoughton@google.com>,
bgardon@google.com, dmatlack@google.com, ricarkol@google.com,
kvm <kvm@vger.kernel.org>,
kvmarm@lists.linux.dev
Subject: Re: [PATCH v3 00/22] Improve scalability of KVM + userfaultfd live migration via annotated memory faults.
Date: Mon, 24 Apr 2023 13:35:36 -0700 [thread overview]
Message-ID: <ZEboGH28IVKPZ2vo@google.com> (raw)
In-Reply-To: <84DD9212-31FB-4AF6-80DD-9BA5AEA0EC1A@gmail.com>
On Mon, Apr 24, 2023, Nadav Amit wrote:
>
> > On Apr 24, 2023, at 10:54 AM, Anish Moorthy <amoorthy@google.com> wrote:
> > Sean did mention that he wanted KVM_CAP_MEMORY_FAULT_INFO in general,
> > so I'm guessing (some version of) that will (eventually :) be merged
> > in any case.
>
> It certainly not my call. But if you ask me, introducing a solution for
> a concrete use-case that requires API changes/enhancements is not
> guaranteed to be the best solution. It may be better first to fully
> understand the existing overheads and agree that there is no alternative
> cleaner and more general solution with similar performance.
KVM already returns -EFAULT for these situations, the change I really want to land
is to have KVM report detailed information about why the -EFAULT occurred. I'll be
happy to carry the code in KVM even if userspace never does anything beyond dumping
the extra information on failures.
> Considering the mess that KVM async-PF introduced, I would be very careful
> before introducing such API changes. I did not look too much on the details,
> but some things anyhow look slightly strange (which might be since I am
> out-of-touch with KVM). For instance, returning -EFAULT on from KVM_RUN? I
> would have assumed -EAGAIN would be more appropriate since the invocation did
> succeed.
Yeah, returning -EFAULT is somewhat odd, but as above, that's pre-existing
behavior that's been around for many years.
next prev parent reply other threads:[~2023-04-24 20:35 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-12 21:34 [PATCH v3 00/22] Improve scalability of KVM + userfaultfd live migration via annotated memory faults Anish Moorthy
2023-04-12 21:34 ` [PATCH v3 01/22] KVM: selftests: Allow many vCPUs and reader threads per UFFD in demand paging test Anish Moorthy
2023-04-19 13:51 ` Hoo Robert
2023-04-20 17:55 ` Anish Moorthy
2023-04-21 12:15 ` Robert Hoo
2023-04-21 16:21 ` Anish Moorthy
2023-04-12 21:34 ` [PATCH v3 02/22] KVM: selftests: Use EPOLL in userfaultfd_util reader threads and signal errors via TEST_ASSERT Anish Moorthy
2023-04-19 13:36 ` Hoo Robert
2023-04-19 23:26 ` Anish Moorthy
2023-04-12 21:34 ` [PATCH v3 03/22] KVM: Allow hva_pfn_fast() to resolve read-only faults Anish Moorthy
2023-04-12 21:34 ` [PATCH v3 04/22] KVM: x86: Set vCPU exit reason to KVM_EXIT_UNKNOWN at the start of KVM_RUN Anish Moorthy
2023-05-02 17:17 ` Anish Moorthy
2023-05-02 18:51 ` Sean Christopherson
2023-05-02 19:49 ` Anish Moorthy
2023-05-02 20:41 ` Sean Christopherson
2023-05-02 21:46 ` Anish Moorthy
2023-05-02 22:31 ` Sean Christopherson
2023-04-12 21:34 ` [PATCH v3 05/22] KVM: Add KVM_CAP_MEMORY_FAULT_INFO Anish Moorthy
2023-04-19 13:57 ` Hoo Robert
2023-04-20 18:09 ` Anish Moorthy
2023-04-21 12:28 ` Robert Hoo
2023-06-01 19:52 ` Oliver Upton
2023-06-01 20:30 ` Anish Moorthy
2023-06-01 21:29 ` Oliver Upton
2023-07-04 10:10 ` Kautuk Consul
2023-04-12 21:34 ` [PATCH v3 06/22] KVM: Add docstrings to __kvm_write_guest_page() and __kvm_read_guest_page() Anish Moorthy
2023-04-12 21:34 ` [PATCH v3 07/22] KVM: Annotate -EFAULTs from kvm_vcpu_write_guest_page() Anish Moorthy
2023-04-20 20:52 ` Peter Xu
2023-04-20 23:29 ` Anish Moorthy
2023-04-21 15:00 ` Peter Xu
2023-04-12 21:34 ` [PATCH v3 08/22] KVM: Annotate -EFAULTs from kvm_vcpu_read_guest_page() Anish Moorthy
2023-04-12 21:34 ` [PATCH v3 09/22] KVM: Annotate -EFAULTs from kvm_vcpu_map() Anish Moorthy
2023-04-20 20:53 ` Peter Xu
2023-04-20 23:34 ` Anish Moorthy
2023-04-21 14:58 ` Peter Xu
2023-04-12 21:34 ` [PATCH v3 10/22] KVM: x86: Annotate -EFAULTs from kvm_mmu_page_fault() Anish Moorthy
2023-04-12 21:34 ` [PATCH v3 11/22] KVM: x86: Annotate -EFAULTs from setup_vmgexit_scratch() Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 12/22] KVM: x86: Annotate -EFAULTs from kvm_handle_page_fault() Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 13/22] KVM: x86: Annotate -EFAULTs from kvm_hv_get_assist_page() Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 14/22] KVM: x86: Annotate -EFAULTs from kvm_pv_clock_pairing() Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 15/22] KVM: x86: Annotate -EFAULTs from direct_map() Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 16/22] KVM: x86: Annotate -EFAULTs from kvm_handle_error_pfn() Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 17/22] KVM: Introduce KVM_CAP_ABSENT_MAPPING_FAULT without implementation Anish Moorthy
2023-04-19 14:00 ` Hoo Robert
2023-04-20 18:23 ` Anish Moorthy
2023-04-24 21:02 ` Sean Christopherson
2023-06-01 16:04 ` Oliver Upton
2023-06-01 18:19 ` Oliver Upton
2023-06-01 18:59 ` Sean Christopherson
2023-06-01 19:29 ` Oliver Upton
2023-06-01 19:34 ` Sean Christopherson
2023-04-12 21:35 ` [PATCH v3 18/22] KVM: x86: Implement KVM_CAP_ABSENT_MAPPING_FAULT Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 19/22] KVM: arm64: Annotate (some) -EFAULTs from user_mem_abort() Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 20/22] KVM: arm64: Implement KVM_CAP_ABSENT_MAPPING_FAULT Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 21/22] KVM: selftests: Add memslot_flags parameter to memstress_create_vm() Anish Moorthy
2023-04-12 21:35 ` [PATCH v3 22/22] KVM: selftests: Handle memory fault exits in demand_paging_test Anish Moorthy
2023-04-19 14:09 ` Hoo Robert
2023-04-19 16:40 ` Anish Moorthy
2023-04-20 22:47 ` Anish Moorthy
2023-04-27 15:48 ` James Houghton
2023-05-01 18:01 ` Anish Moorthy
2023-04-19 19:55 ` [PATCH v3 00/22] Improve scalability of KVM + userfaultfd live migration via annotated memory faults Peter Xu
2023-04-19 20:15 ` Axel Rasmussen
2023-04-19 21:05 ` Peter Xu
2023-04-19 21:53 ` Anish Moorthy
2023-04-20 21:29 ` Peter Xu
2023-04-21 16:58 ` Anish Moorthy
2023-04-21 17:39 ` Nadav Amit
2023-04-24 17:54 ` Anish Moorthy
2023-04-24 19:44 ` Nadav Amit
2023-04-24 20:35 ` Sean Christopherson [this message]
2023-04-24 23:47 ` Nadav Amit
2023-04-25 0:26 ` Sean Christopherson
2023-04-25 0:37 ` Nadav Amit
2023-04-25 0:15 ` Anish Moorthy
2023-04-25 0:54 ` Nadav Amit
2023-04-27 16:38 ` James Houghton
2023-04-27 20:26 ` Peter Xu
2023-05-03 19:45 ` Anish Moorthy
2023-05-03 20:09 ` Sean Christopherson
2023-05-03 21:18 ` Peter Xu
2023-05-03 21:27 ` Peter Xu
2023-05-03 21:42 ` Sean Christopherson
2023-05-03 23:45 ` Peter Xu
2023-05-04 19:09 ` Peter Xu
2023-05-05 18:32 ` Anish Moorthy
2023-05-08 1:23 ` Peter Xu
2023-05-09 20:52 ` Anish Moorthy
2023-05-10 21:50 ` Peter Xu
2023-05-11 17:17 ` David Matlack
2023-05-11 17:33 ` Axel Rasmussen
2023-05-11 19:05 ` David Matlack
2023-05-11 19:45 ` Axel Rasmussen
2023-05-15 15:16 ` Peter Xu
2023-05-15 15:05 ` Peter Xu
2023-05-15 17:16 ` Anish Moorthy
2023-05-05 20:05 ` Nadav Amit
2023-05-08 1:12 ` Peter Xu
2023-04-20 23:42 ` Anish Moorthy
2023-05-09 22:19 ` David Matlack
2023-05-10 16:35 ` Anish Moorthy
2023-05-10 22:35 ` Sean Christopherson
2023-05-10 23:44 ` Anish Moorthy
2023-05-23 17:49 ` Anish Moorthy
2023-06-01 22:43 ` Oliver Upton
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