From: Maxim Levitsky <mlevitsk@redhat.com>
To: Jim Mattson <jmattson@google.com>
Cc: Sean Christopherson <seanjc@google.com>,
alexandru.elisei@arm.com, anup@brainfault.org,
aou@eecs.berkeley.edu, atishp@atishpatra.org,
borntraeger@linux.ibm.com, chenhuacai@kernel.org,
david@redhat.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com,
james.morse@arm.com, kvm-riscv@lists.infradead.org,
kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
linux-riscv@lists.infradead.org, linuxppc-dev@lists.ozlabs.org,
maz@kernel.org, oliver.upton@linux.dev, palmer@dabbelt.com,
paul.walmsley@sifive.com, pbonzini@redhat.com,
suzuki.poulose@arm.com
Subject: Re: [PATCH v4 10/12] KVM: x86: never write to memory from kvm_vcpu_check_block()
Date: Thu, 14 Dec 2023 00:44:12 +0200 [thread overview]
Message-ID: <0c86e5ffb65f07cd3e444038d1f0ed39f0f4130a.camel@redhat.com> (raw)
In-Reply-To: <CALMp9eQ69dGSix-9pJdEtEw9T1Mqz9E1eaf1-yGP9k4_nMZogw@mail.gmail.com>
On Wed, 2023-12-13 at 14:31 -0800, Jim Mattson wrote:
> On Wed, Dec 13, 2023 at 2:25 PM Maxim Levitsky <mlevitsk@redhat.com> wrote:
> > On Tue, 2023-12-12 at 07:28 -0800, Sean Christopherson wrote:
> > > On Sun, Dec 10, 2023, Jim Mattson wrote:
> > > > On Thu, Dec 7, 2023 at 8:21 AM Sean Christopherson <seanjc@google.com> wrote:
> > > > > Doh. We got the less obvious cases and missed the obvious one.
> > > > >
> > > > > Ugh, and we also missed a related mess in kvm_guest_apic_has_interrupt(). That
> > > > > thing should really be folded into vmx_has_nested_events().
> > > > >
> > > > > Good gravy. And vmx_interrupt_blocked() does the wrong thing because that
> > > > > specifically checks if L1 interrupts are blocked.
> > > > >
> > > > > Compile tested only, and definitely needs to be chunked into multiple patches,
> > > > > but I think something like this mess?
> > > >
> > > > The proposed patch does not fix the problem. In fact, it messes things
> > > > up so much that I don't get any test results back.
> > >
> > > Drat.
> > >
> > > > Google has an internal K-U-T test that demonstrates the problem. I
> > > > will post it soon.
> > >
> > > Received, I'll dig in soonish, though "soonish" might unfortunately might mean
> > > 2024.
> > >
> >
> > Hi,
> >
> > So this is what I think:
> >
> >
> > KVM does have kvm_guest_apic_has_interrupt() for this exact purpose,
> > to check if nested APICv has a pending interrupt before halting.
> >
> >
> > However the problem is bigger - with APICv we have in essence 2 pending interrupt
> > bitmaps - the PIR and the IRR, and to know if the guest has a pending interrupt
> > one has in theory to copy PIR to IRR, then see if the max is larger then the current PPR.
> >
> > Since we don't want to write to guest memory, and the IRR here resides in the guest memory,
> > I guess we have to do a 'dry-run' version of 'vmx_complete_nested_posted_interrupt' and call
> > it from kvm_guest_apic_has_interrupt().
> >
> > What do you think? I can prepare a patch for this.
> >
> > Can you share a reproducer or write a new one that can be shared?
>
> See https://lore.kernel.org/kvm/20231211185552.3856862-1-jmattson@google.com/.
Thank you!
Best regards,
Maxim Levitsky
>
> > Best regards,
> > Maxim Levitsky
> >
next prev parent reply other threads:[~2023-12-13 22:44 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 0:31 [PATCH v4 00/12] KVM: x86: never write to memory from kvm_vcpu_check_block Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 01/12] KVM: x86: make vendor code check for all nested events Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 02/12] KVM: nVMX: Make an event request when pending an MTF nested VM-Exit Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 03/12] KVM: x86: Rename and expose helper to detect if INIT/SIPI are allowed Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 04/12] KVM: x86: Rename kvm_apic_has_events() to make it INIT/SIPI specific Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 05/12] KVM: x86: lapic does not have to process INIT if it is blocked Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 06/12] KVM: SVM: Make an event request if INIT or SIPI is pending when GIF is set Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 07/12] KVM: nVMX: Make an event request if INIT or SIPI is pending on VM-Enter Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 08/12] KVM: nVMX: Make event request on VMXOFF iff INIT/SIPI is pending Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 09/12] KVM: x86: Don't snapshot pending INIT/SIPI prior to checking nested events Sean Christopherson
2022-09-21 0:31 ` [PATCH v4 10/12] KVM: x86: never write to memory from kvm_vcpu_check_block() Sean Christopherson
2023-12-07 1:03 ` Jim Mattson
2023-12-07 16:21 ` Sean Christopherson
2023-12-10 22:52 ` Jim Mattson
2023-12-12 15:28 ` Sean Christopherson
2023-12-13 22:25 ` Maxim Levitsky
2023-12-13 22:31 ` Jim Mattson
2023-12-13 22:44 ` Maxim Levitsky [this message]
2023-12-13 22:59 ` Sean Christopherson
2022-09-21 0:32 ` [PATCH v4 11/12] KVM: mips, x86: do not rely on KVM_REQ_UNHALT Sean Christopherson
2022-09-22 13:17 ` Philippe Mathieu-Daudé
2022-09-21 0:32 ` [PATCH v4 12/12] KVM: remove KVM_REQ_UNHALT Sean Christopherson
2022-09-22 14:52 ` Marc Zyngier
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