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RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the interrupt is not single-destination

From "Wu, Feng" <feng.wu@intel.com>
Newsgroups linux.kernel
Subject RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the interrupt is not single-destination
Date 2016-01-26 02:00 +0100
Message-ID <qV09c-3JU-9@gated-at.bofh.it> (permalink)
References (3 earlier) <qTz1o-5gH-7@gated-at.bofh.it> <qTJDs-4tt-11@gated-at.bofh.it> <qUOro-3Og-23@gated-at.bofh.it> <qUOro-3Og-21@gated-at.bofh.it> <qUQ09-54G-9@gated-at.bofh.it>
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> -----Original Message-----
> From: Radim Krcmár [mailto:rkrcmar@redhat.com]
> Sent: Monday, January 25, 2016 10:06 PM
> To: Wu, Feng <feng.wu@intel.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>; linux-kernel@vger.kernel.org;
> kvm@vger.kernel.org
> Subject: Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the
> interrupt is not single-destination
> 
> 2016-01-25 12:26+0000, Wu, Feng:
> >> From: Paolo Bonzini [mailto:paolo.bonzini@gmail.com] On Behalf Of Paolo
> >> It may be necessary because IRTE writes (128 bits) are not atomic.
> >
> > IRTE is updated atomically, I added the patch to support this. Please
> > refer to 344cb4e0b6f3a0dbef0643eacb4946338eb228c0.
> 
> I also think that SN bit is not affected by atomicity: if the IRTE could
> have been read half-updated while changing from posted to non-posted,
> then it wouldn't point to the correct PID, because its address is not
> within 64 bits, so the SN bit wouldn't matter.

Yes, like the comments in the commit, we should atomically update the
IRTE in PI case (PI -> non-PI, non-PI -> PI), without which, it cannot
guarantee the correctness, since 'pda' is not within 64 bits, like Radim
pointed out above.

Thanks,
Feng

> 
> IRTE invalidation seems important in VT-d ...

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Thread

[PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the interrupt is not single-destination Feng Wu <feng.wu@intel.com> - 2016-01-20 03:10 +0100
  Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Yang Zhang <yang.zhang.wz@gmail.com> - 2016-01-21 04:10 +0100
    RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "Wu, Feng" <feng.wu@intel.com> - 2016-01-21 04:20 +0100
      Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Yang Zhang <yang.zhang.wz@gmail.com> - 2016-01-21 04:40 +0100
        RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "Wu, Feng" <feng.wu@intel.com> - 2016-01-21 05:50 +0100
          RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "Tian, Kevin" <kevin.tian@intel.com> - 2016-01-21 06:00 +0100
          Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Yang Zhang <yang.zhang.wz@gmail.com> - 2016-01-21 06:00 +0100
            RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "Wu, Feng" <feng.wu@intel.com> - 2016-01-21 06:10 +0100
              Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Yang Zhang <yang.zhang.wz@gmail.com> - 2016-01-21 06:40 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Yang Zhang <yang.zhang.wz@gmail.com> - 2016-01-21 06:50 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "rkrcmar@redhat.com" <rkrcmar@redhat.com> - 2016-01-21 17:40 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Yang Zhang <yang.zhang.wz@gmail.com> - 2016-01-22 03:10 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "rkrcmar@redhat.com" <rkrcmar@redhat.com> - 2016-01-22 14:40 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Yang Zhang <yang.zhang.wz@gmail.com> - 2016-01-25 03:00 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "rkrcmar@redhat.com" <rkrcmar@redhat.com> - 2016-01-25 15:00 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Yang Zhang <yang.zhang.wz@gmail.com> - 2016-01-26 02:50 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "rkrcmar@redhat.com" <rkrcmar@redhat.com> - 2016-01-26 19:30 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Yang Zhang <yang.zhang.wz@gmail.com> - 2016-01-27 03:10 +0100
                Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "rkrcmar@redhat.com" <rkrcmar@redhat.com> - 2016-01-27 16:10 +0100
                RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "Wu, Feng" <feng.wu@intel.com> - 2016-01-21 06:50 +0100
  Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Radim Krčmář <rkrcmar@redhat.com> - 2016-01-21 17:30 +0100
    RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "Wu, Feng" <feng.wu@intel.com> - 2016-01-22 02:50 +0100
      Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Radim Krcmár <rkrcmar@redhat.com> - 2016-01-22 14:10 +0100
        RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "Wu, Feng" <feng.wu@intel.com> - 2016-01-25 13:30 +0100
          Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Paolo Bonzini <pbonzini@redhat.com> - 2016-01-25 13:40 +0100
            RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "Wu, Feng" <feng.wu@intel.com> - 2016-01-25 13:50 +0100
          Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Radim Krcmár <rkrcmar@redhat.com> - 2016-01-25 15:10 +0100
            RE: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination "Wu, Feng" <feng.wu@intel.com> - 2016-01-26 02:00 +0100
        Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the  interrupt is not single-destination Paolo Bonzini <pbonzini@redhat.com> - 2016-01-25 13:30 +0100

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