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From: "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>
To: "Graf (AWS), Alexander" <graf@amazon.de>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"rkrcmar@redhat.com" <rkrcmar@redhat.com>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"Schoenherr, Jan H." <jschoenh@amazon.de>,
	"Raslan, KarimAllah" <karahmed@amazon.de>,
	"Lukaszewicz, Rimas" <rimasluk@amazon.com>,
	"Grimm, Jon" <Jon.Grimm@amd.com>
Subject: Re: [PATCH v2 11/15] svm: Temporary deactivate AVIC during ExtINT handling
Date: Tue, 10 Sep 2019 15:46:54 +0000
Message-ID: <5f0eb131-d3a5-d1f5-0d7b-be0623e781c9@amd.com> (raw)
In-Reply-To: <82C8A08D-6CB3-4268-BF79-802E1015E365@amazon.de>

Alex,

On 8/28/19 2:37 PM, Graf (AWS), Alexander wrote:
>>>> @@ -5522,9 +5558,6 @@ static void enable_irq_window(struct kvm_vcpu
>>>> *vcpu)
>>>>    {
>>>>        struct vcpu_svm *svm = to_svm(vcpu);
>>>> -    if (kvm_vcpu_apicv_active(vcpu))
>>>> -        return;
>>>> -
>>>>        /*
>>>>         * In case GIF=0 we can't rely on the CPU to tell us when GIF
>>>> becomes
>>>>         * 1, because that's a separate STGI/VMRUN intercept.  The next
>>>> time we
>>>> @@ -5534,6 +5567,14 @@ static void enable_irq_window(struct kvm_vcpu
>>>> *vcpu)
>>>>         * window under the assumption that the hardware will set the GIF.
>>>>         */
>>>>        if ((vgif_enabled(svm) || gif_set(svm)) && nested_svm_intr(svm)) {
>>>> +        /*
>>>> +         * IRQ window is not needed when AVIC is enabled,
>>>> +         * unless we have pending ExtINT since it cannot be injected
>>>> +         * via AVIC. In such case, we need to temporarily disable AVIC,
>>>> +         * and fallback to injecting IRQ via V_IRQ.
>>>> +         */
>>>> +        if (kvm_vcpu_apicv_active(vcpu))
>>>> +            svm_request_deactivate_avic(&svm->vcpu);
>>> Did you test AVIC with nesting? Did you actually run across this issue
>>> there?
>> Currently, we have not claimed that AVIC is supported w/ nested VM.
>> That's why we have not enabled AVIC by default yet. We will be looking
>> more into that next.
> If it's not supported, please suspend it when we enter a nested guest then?

Ok, this makes sense. I'll update this in V3.

> In that case, the above change is also unnecessary, as it only affects nested guests, no?

Actually, the function name nested_svm_intr() is misleading. Here it 
returns true when _NOT_ in guest mode:

/* This function returns true if it is save to enable the irq window */
   static inline bool nested_svm_intr(struct vcpu_svm *svm)
   {
           if (!is_guest_mode(&svm->vcpu))
                   return true;
   ....

So, the logic above does what we want when AVIC is enabled.

Thanks,
Suravee

  reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-15 16:25 [PATCH v2 00/15] kvm: x86: Support AMD SVM AVIC w/ in-kernel irqchip mode Suthikulpanit, Suravee
2019-08-15 16:25 ` [PATCH v2 01/15] kvm: x86: Modify kvm_x86_ops.get_enable_apicv() to use struct kvm parameter Suthikulpanit, Suravee
2019-08-27  7:15   ` Vitaly Kuznetsov
2019-08-15 16:25 ` [PATCH v2 02/15] kvm: x86: Introduce KVM APICv state Suthikulpanit, Suravee
2019-08-19  9:49   ` Alexander Graf
2019-08-26 19:06     ` Suthikulpanit, Suravee
2019-08-15 16:25 ` [PATCH v2 03/15] kvm: Add arch-specific per-VM debugfs support Suthikulpanit, Suravee
2019-08-15 16:25 ` [PATCH v2 04/15] kvm: x86: Add per-VM APICv state debugfs Suthikulpanit, Suravee
2019-08-19  9:57   ` Alexander Graf
2019-08-26 19:41     ` Suthikulpanit, Suravee
2019-08-27  8:20       ` Alexander Graf
2019-08-28 18:39         ` Suthikulpanit, Suravee
2019-08-28 19:36           ` Graf (AWS), Alexander
2019-08-15 16:25 ` [PATCH v2 05/15] kvm: lapic: Introduce APICv update helper function Suthikulpanit, Suravee
2019-08-27  7:22   ` Vitaly Kuznetsov
2019-08-15 16:25 ` [PATCH v2 06/15] kvm: x86: Add support for activate/de-activate APICv at runtime Suthikulpanit, Suravee
2019-08-27  7:29   ` Vitaly Kuznetsov
2019-08-27  8:05     ` Alexander Graf
2019-08-15 16:25 ` [PATCH v2 07/15] kvm: x86: svm: Add support to activate/deactivate posted interrupts Suthikulpanit, Suravee
2019-08-15 16:25 ` [PATCH v2 08/15] svm: Add support for setup/destroy virutal APIC backing page for AVIC Suthikulpanit, Suravee
2019-08-15 16:25 ` [PATCH v2 09/15] svm: Add support for activate/deactivate AVIC at runtime Suthikulpanit, Suravee
2019-08-19 10:28   ` Alexander Graf
2019-08-15 16:25 ` [PATCH v2 10/15] kvm: x86: hyperv: Use APICv deactivate request interface Suthikulpanit, Suravee
2019-08-19 10:31   ` Alexander Graf
2019-08-15 16:25 ` [PATCH v2 11/15] svm: Temporary deactivate AVIC during ExtINT handling Suthikulpanit, Suravee
2019-08-19 10:35   ` Alexander Graf
2019-08-28 15:17     ` Suthikulpanit, Suravee
2019-08-28 19:37       ` Graf (AWS), Alexander
2019-09-10 15:46         ` Suthikulpanit, Suravee [this message]
2019-08-15 16:25 ` [PATCH v2 12/15] kvm: i8254: Check LAPIC EOI pending when injecting irq on SVM AVIC Suthikulpanit, Suravee
2019-08-19 10:42   ` Alexander Graf
2019-08-26 20:46     ` Suthikulpanit, Suravee
2019-08-27  9:10       ` Alexander Graf
2019-09-13 14:50         ` Suthikulpanit, Suravee
2019-08-15 16:25 ` [PATCH v2 13/15] kvm: lapic: Clean up APIC predefined macros Suthikulpanit, Suravee
2019-08-15 16:25 ` [PATCH v2 14/15] kvm: ioapic: Delay update IOAPIC EOI for RTC Suthikulpanit, Suravee
2019-08-19 11:00   ` Alexander Graf
2019-09-04  2:06     ` Suthikulpanit, Suravee
2019-08-15 16:25 ` [PATCH v2 15/15] svm: Allow AVIC with in-kernel irqchip mode Suthikulpanit, Suravee

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