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Date: Mon, 11 Mar 2024 15:43:46 +0100
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Subject: Re: [GIT PULL] KVM: Xen and gfn_to_pfn_cache changes for 6.9
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To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
 Christian Borntraeger <borntraeger@linux.ibm.com>,
 Janosch Frank <frankja@linux.ibm.com>,
 Claudio Imbrenda <imbrenda@linux.ibm.com>,
 David Hildenbrand <david@redhat.com>
References: <20240308223702.1350851-1-seanjc@google.com>
 <20240308223702.1350851-9-seanjc@google.com>
From: Paolo Bonzini <pbonzini@redhat.com>
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In-Reply-To: <20240308223702.1350851-9-seanjc@google.com>
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On 3/8/24 23:37, Sean Christopherson wrote:
> Aaaand seeing my one commit in the shortlog made me realize I completely forgot
> to get acks from s390 on the kvm_is_error_gpa() => kvm_is_gpa_in_memslot()
> refactor.  Fudge.
> 
> s390 folks, my apologies for not reaching out earlier.  Please take a look at
> commit 9e7325acb3dc ("KVM: s390: Refactor kvm_is_error_gpa() into
> kvm_is_gpa_in_memslot()").  It *should* be a straight refactor, and I don't
> expect the rename to be contentious, but I didn't intend to send this pull request
> before getting an explicit ack.
> 
> As for the actual pull request, the bulk of the changes are to add support
> for using gfn_to_pfn caches without a gfn, e.g. to opimize handling of overlay
> pages, and then use that functionality for Xen's shared_info page.
> 
> Note, the commits towards the end are a variety of fixes from David that have
> been on the list for a while, but only got applied this week due to issues with
> the patches being corrupted (thanks to Evolution doing weird things).

Evolution?!? :)

> The following changes since commit db7d6fbc10447090bab8691a907a7c383ec66f58:
> 
>    KVM: remove unnecessary #ifdef (2024-02-08 08:41:06 -0500)
> 
> are available in the Git repository at:
> 
>    https://github.com/kvm-x86/linux.git tags/kvm-x86-xen-6.9
> 
> for you to fetch changes up to 7a36d680658ba5a0d350f2ad275b97156b8d4333:
> 
>    KVM: x86/xen: fix recursive deadlock in timer injection (2024-03-04 16:22:39 -0800)

Pulled, thanks.

Paolo

> ----------------------------------------------------------------
> KVM Xen and pfncache changes for 6.9:
> 
>   - Rip out the half-baked support for using gfn_to_pfn caches to manage pages
>     that are "mapped" into guests via physical addresses.
> 
>   - Add support for using gfn_to_pfn caches with only a host virtual address,
>     i.e. to bypass the "gfn" stage of the cache.  The primary use case is
>     overlay pages, where the guest may change the gfn used to reference the
>     overlay page, but the backing hva+pfn remains the same.
> 
>   - Add an ioctl() to allow mapping Xen's shared_info page using an hva instead
>     of a gpa, so that userspace doesn't need to reconfigure and invalidate the
>     cache/mapping if the guest changes the gpa (but userspace keeps the resolved
>     hva the same).
> 
>   - When possible, use a single host TSC value when computing the deadline for
>     Xen timers in order to improve the accuracy of the timer emulation.
> 
>   - Inject pending upcall events when the vCPU software-enables its APIC to fix
>     a bug where an upcall can be lost (and to follow Xen's behavior).
> 
>   - Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen
>     events fails, e.g. if the guest has aliased xAPIC IDs.
> 
>   - Extend gfn_to_pfn_cache's mutex to cover (de)activation (in addition to
>     refresh), and drop a now-redundant acquisition of xen_lock (that was
>     protecting the shared_info cache) to fix a deadlock due to recursively
>     acquiring xen_lock.
> 
> ----------------------------------------------------------------
> David Woodhouse (5):
>        KVM: x86/xen: improve accuracy of Xen timers
>        KVM: x86/xen: inject vCPU upcall vector when local APIC is enabled
>        KVM: x86/xen: remove WARN_ON_ONCE() with false positives in evtchn delivery
>        KVM: pfncache: simplify locking and make more self-contained
>        KVM: x86/xen: fix recursive deadlock in timer injection
> 
> Paul Durrant (17):
>        KVM: pfncache: Add a map helper function
>        KVM: pfncache: remove unnecessary exports
>        KVM: x86/xen: mark guest pages dirty with the pfncache lock held
>        KVM: pfncache: add a mark-dirty helper
>        KVM: pfncache: remove KVM_GUEST_USES_PFN usage
>        KVM: pfncache: stop open-coding offset_in_page()
>        KVM: pfncache: include page offset in uhva and use it consistently
>        KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA
>        KVM: x86/xen: separate initialization of shared_info cache and content
>        KVM: x86/xen: re-initialize shared_info if guest (32/64-bit) mode is set
>        KVM: x86/xen: allow shared_info to be mapped by fixed HVA
>        KVM: x86/xen: allow vcpu_info to be mapped by fixed HVA
>        KVM: selftests: map Xen's shared_info page using HVA rather than GFN
>        KVM: selftests: re-map Xen's vcpu_info using HVA rather than GPA
>        KVM: x86/xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability
>        KVM: pfncache: check the need for invalidation under read lock first
>        KVM: x86/xen: allow vcpu_info content to be 'safely' copied
> 
> Sean Christopherson (1):
>        KVM: s390: Refactor kvm_is_error_gpa() into kvm_is_gpa_in_memslot()
> 
>   Documentation/virt/kvm/api.rst                     |  51 +++-
>   arch/s390/kvm/diag.c                               |   2 +-
>   arch/s390/kvm/gaccess.c                            |  14 +-
>   arch/s390/kvm/kvm-s390.c                           |   4 +-
>   arch/s390/kvm/priv.c                               |   4 +-
>   arch/s390/kvm/sigp.c                               |   2 +-
>   arch/x86/include/uapi/asm/kvm.h                    |   9 +-
>   arch/x86/kvm/lapic.c                               |   5 +-
>   arch/x86/kvm/x86.c                                 |  68 ++++-
>   arch/x86/kvm/x86.h                                 |   1 +
>   arch/x86/kvm/xen.c                                 | 325 ++++++++++++++-------
>   arch/x86/kvm/xen.h                                 |  18 ++
>   include/linux/kvm_host.h                           |  56 +++-
>   include/linux/kvm_types.h                          |   8 -
>   .../testing/selftests/kvm/x86_64/xen_shinfo_test.c |  59 +++-
>   virt/kvm/pfncache.c                                | 245 +++++++++-------
>   16 files changed, 602 insertions(+), 269 deletions(-)
>