From: Maxim Levitsky <mlevitsk@redhat.com>
To: "Suthikulpanit, Suravee" <suravee.suthikulpanit@amd.com>,
Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: seanjc@google.com, joro@8bytes.org, jon.grimm@amd.com,
wei.huang2@amd.com, terry.bowman@amd.com
Subject: Re: [PATCH v6 15/17] KVM: SVM: Use target APIC ID to complete x2AVIC IRQs when possible
Date: Tue, 28 Jun 2022 11:59:55 +0300 [thread overview]
Message-ID: <df464fd9b3c66059d7065acc52594d27dfe52448.camel@redhat.com> (raw)
In-Reply-To: <9f3ffe16-2516-d4ec-528e-6347ef884ad5@amd.com>
On Tue, 2022-06-28 at 09:35 +0700, Suthikulpanit, Suravee wrote:
>
> On 6/28/2022 5:55 AM, Maxim Levitsky wrote:
> > On Fri, 2022-06-24 at 18:41 +0200, Paolo Bonzini wrote:
> > > On 5/19/22 12:27, Suravee Suthikulpanit wrote:
> > > > + * If the x2APIC logical ID sub-field (i.e. icrh[15:0]) contains zero
> > > > + * or more than 1 bits, we cannot match just one vcpu to kick for
> > > > + * fast path.
> > > > + */
> > > > + if (!first || (first != last))
> > > > + return -EINVAL;
> > > > +
> > > > + apic = first - 1;
> > > > + if ((apic < 0) || (apic > 15) || (cluster >= 0xfffff))
> > > > + return -EINVAL;
> > >
> > > Neither of these is possible: first == 0 has been cheked above, and
> > > ffs(icrh & 0xffff) cannot exceed 15. Likewise, cluster is actually
> > > limited to 16 bits, not 20.
> > >
> > > Plus, C is not Pascal so no parentheses. :)
> > >
> > > Putting everything together, it can be simplified to this:
> > >
> > > + int cluster = (icrh & 0xffff0000) >> 16;
> > > + int apic = ffs(icrh & 0xffff) - 1;
> > > +
> > > + /*
> > > + * If the x2APIC logical ID sub-field (i.e. icrh[15:0])
> > > + * contains anything but a single bit, we cannot use the
> > > + * fast path, because it is limited to a single vCPU.
> > > + */
> > > + if (apic < 0 || icrh != (1 << apic))
> > > + return -EINVAL;
> > > +
> > > + l1_physical_id = (cluster << 4) + apic;
> > >
> > >
> > > > + apic_id = (cluster << 4) + apic;
> >
> > Hi Paolo and Suravee Suthikulpanit!
> >
> > Note that this patch is not needed anymore, I fixed the avic_kick_target_vcpus_fast function,
> > and added the support for x2apic because it was very easy to do
> > (I already needed to parse logical id for flat and cluser modes)
> >
> > Best regards,
> > Maxim Levitsky
> >
>
> Understood. I was about to send v7 to remove this patch from the series, but too late. I'll test the current queue branch and provide update.
Also this really needs a KVM unit test, to avoid breaking corner cases like
sending IPI to 0xFF address, which was the reason I had to fix the
avic_kick_target_vcpus_fast.
We do have 'apic' test in kvm unit tests,
and I was already looking to extend it to cover more cases and to run it with AVIC's
compatible settings. I hope I will be able to do this this week.
Best regards,
Maxim Levitsky
>
> Best Regards,
> Suravee
>
next prev parent reply other threads:[~2022-06-28 9:00 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-19 10:26 [PATCH v6 00/17] Introducing AMD x2AVIC and hybrid-AVIC modes Suravee Suthikulpanit
2022-05-19 10:26 ` [PATCH v6 01/17] x86/cpufeatures: Introduce x2AVIC CPUID bit Suravee Suthikulpanit
2022-06-24 16:08 ` Paolo Bonzini
2022-05-19 10:26 ` [PATCH v6 02/17] KVM: x86: lapic: Rename [GET/SET]_APIC_DEST_FIELD to [GET/SET]_XAPIC_DEST_FIELD Suravee Suthikulpanit
2022-06-24 16:08 ` Paolo Bonzini
2022-05-19 10:26 ` [PATCH v6 03/17] KVM: SVM: Detect X2APIC virtualization (x2AVIC) support Suravee Suthikulpanit
2022-05-19 10:26 ` [PATCH v6 04/17] KVM: SVM: Update max number of vCPUs supported for x2AVIC mode Suravee Suthikulpanit
2022-05-19 10:26 ` [PATCH v6 05/17] KVM: SVM: Update avic_kick_target_vcpus to support 32-bit APIC ID Suravee Suthikulpanit
2022-05-19 10:26 ` [PATCH v6 06/17] KVM: SVM: Do not support updating APIC ID when in x2APIC mode Suravee Suthikulpanit
2022-05-19 10:26 ` [PATCH v6 07/17] KVM: SVM: Adding support for configuring x2APIC MSRs interception Suravee Suthikulpanit
2022-05-19 10:27 ` [PATCH v6 08/17] KVM: x86: Deactivate APICv on vCPU with APIC disabled Suravee Suthikulpanit
2022-05-19 10:27 ` [PATCH v6 09/17] KVM: SVM: Refresh AVIC configuration when changing APIC mode Suravee Suthikulpanit
2022-05-19 10:27 ` [PATCH v6 10/17] KVM: x86: nSVM: always intercept x2apic msrs Suravee Suthikulpanit
2022-05-19 10:27 ` [PATCH v6 11/17] KVM: SVM: Introduce logic to (de)activate x2AVIC mode Suravee Suthikulpanit
2022-05-19 10:27 ` [PATCH v6 12/17] KVM: SVM: Do not throw warning when calling avic_vcpu_load on a running vcpu Suravee Suthikulpanit
2022-05-19 10:27 ` [PATCH v6 13/17] KVM: SVM: Introduce hybrid-AVIC mode Suravee Suthikulpanit
2022-05-19 10:27 ` [PATCH v6 14/17] KVM: x86: Warning APICv inconsistency only when vcpu APIC mode is valid Suravee Suthikulpanit
2022-05-19 10:27 ` [PATCH v6 15/17] KVM: SVM: Use target APIC ID to complete x2AVIC IRQs when possible Suravee Suthikulpanit
2022-06-24 16:41 ` Paolo Bonzini
2022-06-27 22:55 ` Maxim Levitsky
2022-06-28 2:35 ` Suthikulpanit, Suravee
2022-06-28 8:59 ` Maxim Levitsky [this message]
2022-06-28 12:36 ` Suthikulpanit, Suravee
2022-06-28 13:14 ` Maxim Levitsky
2022-05-19 10:27 ` [PATCH v6 16/17] KVM: SVM: Add AVIC doorbell tracepoint Suravee Suthikulpanit
2022-05-19 10:27 ` [PATCH v6 17/17] KVM: x86: nSVM: optimize svm_set_x2apic_msr_interception Suravee Suthikulpanit
2022-06-06 23:05 ` [PATCH v6 00/17] Introducing AMD x2AVIC and hybrid-AVIC modes Jim Mattson
2022-06-24 17:04 ` Paolo Bonzini
2022-06-28 13:20 ` Suthikulpanit, Suravee
2022-06-28 13:43 ` Maxim Levitsky
2022-06-28 16:34 ` Suthikulpanit, Suravee
2022-06-29 7:10 ` Maxim Levitsky
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