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From: "Graf (AWS), Alexander" <graf@amazon.de>
To: "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>
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: Wed, 28 Aug 2019 19:37:24 +0000
Message-ID: <82C8A08D-6CB3-4268-BF79-802E1015E365@amazon.de> (raw)
In-Reply-To: <5aaef6f4-4bee-4cc4-8eb0-d9b4c412988b@amd.com>



> Am 28.08.2019 um 17:19 schrieb Suthikulpanit, Suravee <Suravee.Suthikulpanit@amd.com>:
> 
> Alex,
> 
>> On 8/19/19 5:35 AM, Alexander Graf wrote:
>> 
>> 
>>> On 15.08.19 18:25, Suthikulpanit, Suravee wrote:
>>> AMD AVIC does not support ExtINT. Therefore, AVIC must be temporary
>>> deactivated and fall back to using legacy interrupt injection via vINTR
>>> and interrupt window.
>>> 
>>> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
>>> ---
>>>   arch/x86/kvm/svm.c | 49 
>>> +++++++++++++++++++++++++++++++++++++++++++++----
>>>   1 file changed, 45 insertions(+), 4 deletions(-)
>>> 
>>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>>> index cfa4b13..4690351 100644
>>> --- a/arch/x86/kvm/svm.c
>>> +++ b/arch/x86/kvm/svm.c
>>> @@ -384,6 +384,7 @@ struct amd_svm_iommu_ir {
>>>   static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
>>>   static void svm_flush_tlb(struct kvm_vcpu *vcpu, bool invalidate_gpa);
>>>   static void svm_complete_interrupts(struct vcpu_svm *svm);
>>> +static void svm_request_activate_avic(struct kvm_vcpu *vcpu);
>>>   static bool svm_get_enable_apicv(struct kvm *kvm);
>>>   static inline void avic_post_state_restore(struct kvm_vcpu *vcpu);
>>> @@ -4494,6 +4495,15 @@ static int interrupt_window_interception(struct 
>>> vcpu_svm *svm)
>>>   {
>>>       kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);
>>>       svm_clear_vintr(svm);
>>> +
>>> +    /*
>>> +     * For AVIC, the only reason to end up here is ExtINTs.
>>> +     * In this case AVIC was temporarily disabled for
>>> +     * requesting the IRQ window and we have to re-enable it.
>>> +     */
>>> +    if (svm_get_enable_apicv(svm->vcpu.kvm))
>>> +        svm_request_activate_avic(&svm->vcpu);
>> 
>> Would it make sense to add a trace point here and to the other call 
>> sites, so that it becomes obvious in a trace when and why exactly avic 
>> was active/inactive?
>> 
>> The trace point could add additional information on the why.
> 
> Sure, sounds good.
> 
>>> ....
>>> @@ -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? In that case, the above change is also unnecessary, as it only affects nested guests, no?

Alex

> 
> Suravee



Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Ralf Herbrich
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879




  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 [this message]
2019-09-10 15:46         ` Suthikulpanit, Suravee
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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