From: Paolo Bonzini <bonzini@gnu.org>
To: David Woodhouse <dwmw2@infradead.org>,
Sean Christopherson <seanjc@google.com>
Cc: kvm <kvm@vger.kernel.org>,
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>,
"vkuznets@redhat.com" <vkuznets@redhat.com>,
"mtosatti@redhat.com" <mtosatti@redhat.com>,
"joro@8bytes.org" <joro@8bytes.org>,
karahmed@amazon.com
Subject: Re: [RFC PATCH 0/11] Rework gfn_to_pfn_cache
Date: Tue, 16 Nov 2021 19:46:03 +0100 [thread overview]
Message-ID: <cfa1a13d-5ad2-3ca4-147e-84273ffa2f38@gnu.org> (raw)
In-Reply-To: <7bcb9dafa55c283f9f9d0b841f4a53f0b6b3286d.camel@infradead.org>
On 11/16/21 18:57, David Woodhouse wrote:
>>> + read_lock(&gpc->lock);
>>> + if (!kvm_gfn_to_pfn_cache_check(vcpu->kvm, gpc, gpc->gpa, PAGE_SIZE)) {
>>> + read_unlock(&gpc->lock);
>>> goto mmio_needed;
>>> + }
>>> +
>>> + vapic_page = gpc->khva;
>> If we know this gpc is of the synchronous kind, I think we can skip the
>> read_lock/read_unlock here?!?
> Er... this one was OUTSIDE_GUEST_MODE and is the atomic kind, which
> means it needs to hold the lock for the duration of the access in order
> to prevent (preemption and) racing with the invalidate?
>
> It's the IN_GUEST_MODE one (in my check_guest_maps()) where we might
> get away without the lock, perhaps?
Ah, this is check_nested_events which is mostly IN_GUEST_MODE but not
always (and that sucks for other reasons). I'll think a bit more about
it when I actually do the work.
>>> __kvm_apic_update_irr(vmx->nested.pi_desc->pir,
>>> vapic_page, &max_irr);
>>> @@ -3749,6 +3783,7 @@ static int vmx_complete_nested_posted_interrupt(struct kvm_vcpu *vcpu)
>>> status |= (u8)max_irr;
>>> vmcs_write16(GUEST_INTR_STATUS, status);
>>> }
>>> + read_unlock(&gpc->lock);
>>> }
>>>
> I just realised that the mark_page_dirty() on invalidation and when the
> the irqfd workqueue refreshes the gpc might fall foul of the same
> dirty_ring problem that I belatedly just spotted with the Xen shinfo
> clock write. I'll fix it up to*always* require a vcpu (to be
> associated with the writes), and reinstate the guest_uses_pa flag since
> that can no longer in implicit in (vcpu!=NULL).
Okay.
> I may leave the actual task of fixing nesting to you, if that's OK, as
> long as we consider the new gfn_to_pfn_cache sufficient to address the
> problem? I think it's mostly down to how we*use* it now, rather than
> the fundamental design of cache itself?
Yes, I agree. Just stick whatever you have for nesting as an extra
patch at the end, and I'll take it from there.
Paolo
next prev parent reply other threads:[~2021-11-16 18:46 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
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 [this message]
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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