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Groups > linux.kernel > #1297547
| From | "rkrcmar@redhat.com" <rkrcmar@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts |
| Date | 2015-12-23 18:00 +0100 |
| Message-ID | <qIUVA-3GD-19@gated-at.bofh.it> (permalink) |
| References | (2 earlier) <qHXVv-8tg-3@gated-at.bofh.it> <qHXVv-8tg-1@gated-at.bofh.it> <qHY5c-k9-3@gated-at.bofh.it> <qImTT-7BR-9@gated-at.bofh.it> <qIoVH-qe-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
2015-12-22 14:42+0800, Yang Zhang:
> On 2015/12/22 12:36, Wu, Feng wrote:
>>>From: Yang Zhang [mailto:yang.zhang.wz@gmail.com]
>>>On 2015/12/21 9:55, Wu, Feng wrote:
>>>>>From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-
>>>>>On 2015/12/16 9:37, Feng Wu wrote:
>>>>>>diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>>>>>@@ -10702,8 +10702,16 @@ static int vmx_update_pi_irte(struct kvm
>>>*kvm,
>>>>>unsigned int host_irq,
>>>>>> */
>>>>>>
>>>>>> kvm_set_msi_irq(e, &irq);
>>>>>>- if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu))
>>>>>>- continue;
>>>>>>+
>>>>>>+ if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu)) {
>>>>>>+ if (!kvm_vector_hashing_enabled() ||
>>>>>>+ irq.delivery_mode !=
>>>>>APIC_DM_LOWEST)
>>>>>>+ continue;
>>>>>>+
>>>>>>+ vcpu = kvm_intr_vector_hashing_dest(kvm, &irq);
>>>>>>+ if (!vcpu)
>>>>>>+ continue;
>>>>>>+ }
>>>>>
>>>>>I am a little confused with the 'continue'. If the destination is not
>>>>>single vcpu, shouldn't we rollback to use non-PI mode?
>>>>
>>>>Here is the logic:
>>>>- If it is single destination, we will use PI no matter it is fixed or lowest-priority.
>>>>- If it is not single destination:
>>>> a) It is fixed, we will use non-PI
>>>> b) It is lowest-priority and vector-hashing is enabled, we will use PI
>>>> c) otherwise, use non-PI
>>>
>>>If it is single destination previously, then change to no-single mode.
>>>Can current code cover this case?
>>
>>In my test, before setting irq affinity (change single vcpu to non-single vcpu
>>in this case), the guest will mask the interrupt first, so before getting here, IRTE
>>has been changed back to remapped mode already(when guest masks the MSIx,
>>we will change back to remapped mode), hence nothing needed here.
>>
>>Digging into the linux code (guest) a bit more, I found that if interrupt remapping
>>is not enabled in the guest (IR is not supported for guest anyway), it will always
>>mask the MSI/MSIx before setting the irq affinity. So the code should work
>>well currently.
>
> We should not rely on guest's behavior. From code level, it need be fixed.
>
>>However, for robustness, I think explicitly changing IRTE back to remapped
>>mode for the 'continue' case should be a good idea.
>
> This is what i am looking for.
I agree, that would be a nice addition.
IIRC, the masking is optional -- if the guest can handle interrupts that
are generated while the device is half-configured, it doesn't need to
disable MSIs.
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[PATCH v2 0/2] Add vector-hashing support for lowest-priority interrupts delivery Feng Wu <feng.wu@intel.com> - 2015-12-16 03:00 +0100
[PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts Feng Wu <feng.wu@intel.com> - 2015-12-16 03:00 +0100
RE: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-12-21 03:00 +0100
Re: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts Yang Zhang <yang.zhang.wz@gmail.com> - 2015-12-21 03:10 +0100
RE: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-12-22 05:40 +0100
Re: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts Yang Zhang <yang.zhang.wz@gmail.com> - 2015-12-22 07:50 +0100
Re: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts "rkrcmar@redhat.com" <rkrcmar@redhat.com> - 2015-12-23 18:00 +0100
Re: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts Yang Zhang <yang.zhang.wz@gmail.com> - 2015-12-21 03:00 +0100
Re: [PATCH v2 2/2] KVM: x86: Add lowest-priority support for vt-d posted-interrupts Radim Krčmář <rkrcmar@redhat.com> - 2015-12-23 18:30 +0100
[PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts Feng Wu <feng.wu@intel.com> - 2015-12-16 03:00 +0100
Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts Yang Zhang <yang.zhang.wz@gmail.com> - 2015-12-21 02:50 +0100
RE: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-12-21 03:00 +0100
Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts Yang Zhang <yang.zhang.wz@gmail.com> - 2015-12-21 03:10 +0100
RE: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-12-22 05:40 +0100
Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts Yang Zhang <yang.zhang.wz@gmail.com> - 2015-12-22 07:50 +0100
RE: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-12-22 08:00 +0100
RE: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-12-22 08:20 +0100
Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts "rkrcmar@redhat.com" <rkrcmar@redhat.com> - 2015-12-22 21:00 +0100
RE: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-12-23 03:20 +0100
Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts "rkrcmar@redhat.com" <rkrcmar@redhat.com> - 2015-12-23 17:50 +0100
Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts Yang Zhang <yang.zhang.wz@gmail.com> - 2015-12-23 04:20 +0100
Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts Yang Zhang <yang.zhang.wz@gmail.com> - 2015-12-22 08:20 +0100
Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts Radim Krčmář <rkrcmar@redhat.com> - 2015-12-23 18:20 +0100
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