From: Paolo Bonzini <pbonzini@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>, kvm <kvm@vger.kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Joao Martins <joao.m.martins@oracle.com>,
"jmattson@google.com" <jmattson@google.com>,
"wanpengli@tencent.com" <wanpengli@tencent.com>,
"seanjc@google.com" <seanjc@google.com>,
"vkuznets@redhat.com" <vkuznets@redhat.com>,
"mtosatti@redhat.com" <mtosatti@redhat.com>,
"joro@8bytes.org" <joro@8bytes.org>,
karahmed@amazon.com
Subject: Re: [PATCH v3] KVM: x86: Fix recording of guest steal time / preempted status
Date: Fri, 12 Nov 2021 15:56:02 +0100 [thread overview]
Message-ID: <7e4b895b-8f36-69cb-10a9-0b4139b9eb79@redhat.com> (raw)
In-Reply-To: <537fdcc6af80ba6285ae0cdecdb615face25426f.camel@infradead.org>
On 11/12/21 14:28, David Woodhouse wrote:
> A back-to-back write_lock/write_unlock*without* setting the address to
> KVM_UNMAPPED_PAGE? I'm not sure I see how that protects the IRQ
> delivery from accessing the (now stale) physical page after the MMU
> notifier has completed? Not unless it's going to call hva_to_pfn again
> for itself under the read_lock, every time it delivers an IRQ?
Yeah, you're right, it still has to invalidate it somehow. So
KVM_UNMAPPED_PAGE would go in the hva field of the gfn_to_pfn cache
(merged with kvm_host_map). Or maybe one can use an invalid generation,
too.
I was under the mistaken impression that with MMU notifiers one could
make atomic kvm_vcpu_map never fail, but now I think that makes no sense;
it could always encounter stale memslots.
>> 2) for memremap/memunmap, all you really care about is reacting to
>> changes in the memslots, so the MMU notifier integration has nothing
>> to do. You still need to call the same hook as
>> kvm_mmu_notifier_invalidate_range() when memslots change, so that
>> the update is done outside atomic context.
>
> Hm, we definitely *do* care about reacting to MMU notifiers in this
> case too. Userspace can do memory overcommit / ballooning etc.
> *without* changing the memslots, and only mmap/munmap/userfault_fd on
> the corresponding HVA ranges.
Can it do so for VM_IO/VM_PFNMAP memory?
> I think we want to kill the struct kvm_host_map completely, merge its
> extra 'hva' and 'page' fields into the (possibly renamed)
> gfn_to_pfn_cache along with your 'guest_uses_pa' flag, and take it from
> there.
Yes, that makes sense.
Paolo
next prev parent reply other threads:[~2021-11-12 14:56 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 14:09 [PATCH] KVM: x86: Fix recording of guest steal time / preempted status David Woodhouse
2021-11-02 16:38 ` [PATCH v2] " David Woodhouse
2021-11-02 17:01 ` Paolo Bonzini
2021-11-02 17:11 ` David Woodhouse
2021-11-02 17:19 ` Paolo Bonzini
2021-11-02 17:26 ` David Woodhouse
2021-11-02 17:36 ` [PATCH v3] " David Woodhouse
2021-11-11 13:23 ` Paolo Bonzini
2021-11-12 8:28 ` David Woodhouse
2021-11-12 9:31 ` Paolo Bonzini
2021-11-12 9:54 ` David Woodhouse
2021-11-12 10:49 ` Paolo Bonzini
2021-11-12 11:29 ` David Woodhouse
2021-11-12 12:27 ` Paolo Bonzini
2021-11-12 13:28 ` David Woodhouse
2021-11-12 14:56 ` Paolo Bonzini [this message]
2021-11-12 15:27 ` David Woodhouse
2021-11-15 16:47 ` [RFC PATCH 0/11] Rework gfn_to_pfn_cache David Woodhouse
2021-11-15 16:50 ` [PATCH 01/11] KVM: x86: Fix steal time asm constraints in 32-bit mode David Woodhouse
2021-11-15 16:50 ` [PATCH 02/11] KVM: x86/xen: Fix get_attr of KVM_XEN_ATTR_TYPE_SHARED_INFO David Woodhouse
2021-11-15 16:50 ` [PATCH 03/11] KVM: selftests: Add event channel upcall support to xen_shinfo_test David Woodhouse
2021-11-15 16:50 ` [PATCH 04/11] KVM: x86/xen: Use sizeof_field() instead of open-coding it David Woodhouse
2021-11-15 16:50 ` [PATCH 05/11] KVM: nVMX: Use kvm_{read,write}_guest_cached() for shadow_vmcs12 David Woodhouse
2021-11-15 16:50 ` [PATCH 06/11] KVM: nVMX: Use kvm_read_guest_offset_cached() for nested VMCS check David Woodhouse
2021-11-15 16:50 ` [PATCH 07/11] KVM: nVMX: Use a gfn_to_hva_cache for vmptrld David Woodhouse
2021-11-15 16:50 ` [PATCH 08/11] KVM: Kill kvm_map_gfn() / kvm_unmap_gfn() and gfn_to_pfn_cache David Woodhouse
2021-11-16 10:21 ` Paolo Bonzini
2021-11-17 17:18 ` David Woodhouse
2021-11-15 16:50 ` [PATCH 09/11] KVM: Reinstate gfn_to_pfn_cache with invalidation support David Woodhouse
2021-11-15 16:50 ` [PATCH 10/11] KVM: x86/xen: Maintain valid mapping of Xen shared_info page David Woodhouse
2021-11-15 16:50 ` [PATCH 11/11] KVM: x86/xen: Add KVM_IRQ_ROUTING_XEN_EVTCHN and event channel delivery David Woodhouse
2021-11-15 17:02 ` David Woodhouse
2021-11-15 18:49 ` Paolo Bonzini
2021-11-15 18:55 ` David Woodhouse
2021-11-15 18:50 ` [RFC PATCH 0/11] Rework gfn_to_pfn_cache Paolo Bonzini
2021-11-15 19:11 ` David Woodhouse
2021-11-15 19:26 ` Paolo Bonzini
2021-11-15 22:59 ` Sean Christopherson
2021-11-15 23:22 ` David Woodhouse
2021-11-16 13:17 ` David Woodhouse
2021-11-16 14:11 ` Paolo Bonzini
2021-11-16 14:25 ` David Woodhouse
2021-11-16 14:57 ` Paolo Bonzini
2021-11-16 15:09 ` David Woodhouse
2021-11-16 15:49 ` Paolo Bonzini
2021-11-16 16:06 ` David Woodhouse
2021-11-16 17:42 ` Paolo Bonzini
2021-11-16 17:57 ` David Woodhouse
2021-11-16 18:46 ` Paolo Bonzini
2021-11-16 19:34 ` David Woodhouse
2021-11-15 23:24 ` David Woodhouse
2021-11-16 11:50 ` [PATCH 0/7] KVM: Add Makefile.kvm for common files David Woodhouse
2021-11-16 11:50 ` [PATCH 1/7] KVM: Introduce CONFIG_HAVE_KVM_DIRTY_RING David Woodhouse
2021-11-16 11:50 ` [PATCH 2/7] KVM: Add Makefile.kvm for common files, use it for x86 David Woodhouse
2021-11-16 11:50 ` [PATCH 3/7] KVM: s390: Use Makefile.kvm for common files David Woodhouse
2021-11-17 7:29 ` Christian Borntraeger
2021-11-16 11:50 ` [PATCH 4/7] KVM: mips: " David Woodhouse
2021-11-16 11:50 ` [PATCH 5/7] KVM: RISC-V: " David Woodhouse
2021-11-16 11:50 ` [PATCH 6/7] KVM: powerpc: " David Woodhouse
2021-11-16 18:43 ` Sean Christopherson
2021-11-16 19:13 ` David Woodhouse
2021-11-16 11:50 ` [PATCH 7/7] KVM: arm64: " David Woodhouse
2021-11-15 21:38 ` [RFC PATCH 0/11] Rework gfn_to_pfn_cache David Woodhouse
2021-11-12 19:44 ` [PATCH v3] KVM: x86: Fix recording of guest steal time / preempted status David Woodhouse
2021-11-03 9:47 ` [PATCH v2] " David Woodhouse
2021-11-03 12:35 ` Paolo Bonzini
2021-11-03 12:56 ` David Woodhouse
2021-11-03 13:05 ` Paolo Bonzini
2021-11-03 13:23 ` David Woodhouse
2021-11-03 13:34 ` David Woodhouse
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