> -----Original Message----- > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > Sent: Monday, December 08, 2014 1:21 PM > To: Wu, Feng > Cc: Eric Auger; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; hpa@xxxxxxxxx; > x86@xxxxxxxxxx; gleb@xxxxxxxxxx; pbonzini@xxxxxxxxxx; > dwmw2@xxxxxxxxxxxxx; joro@xxxxxxxxxx; jiang.liu@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; > kvm@xxxxxxxxxxxxxxx > Subject: Re: [v2 17/25] KVM: kvm-vfio: User API for VT-d Posted-Interrupts > > On Mon, 2014-12-08 at 04:58 +0000, Wu, Feng wrote: > > > > > -----Original Message----- > > > From: kvm-owner@xxxxxxxxxxxxxxx [mailto:kvm-owner@xxxxxxxxxxxxxxx] > On > > > Behalf Of Eric Auger > > > Sent: Thursday, December 04, 2014 10:05 PM > > > To: Wu, Feng; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; hpa@xxxxxxxxx; > > > x86@xxxxxxxxxx; gleb@xxxxxxxxxx; pbonzini@xxxxxxxxxx; > > > dwmw2@xxxxxxxxxxxxx; joro@xxxxxxxxxx; alex.williamson@xxxxxxxxxx; > > > jiang.liu@xxxxxxxxxxxxxxx > > > Cc: linux-kernel@xxxxxxxxxxxxxxx; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; > > > kvm@xxxxxxxxxxxxxxx > > > Subject: Re: [v2 17/25] KVM: kvm-vfio: User API for VT-d Posted-Interrupts > > > > > > Hi Feng, > > > On 12/03/2014 08:39 AM, Feng Wu wrote: > > > > This patch adds and documents a new attribute > > > > KVM_DEV_VFIO_DEVICE_POSTING_IRQ in KVM_DEV_VFIO_DEVICE > group. > > > > This new attribute is used for VT-d Posted-Interrupts. > > > > > > > > When guest OS changes the interrupt configuration for an > > > > assigned device, such as, MSI/MSIx data/address fields, > > > > QEMU will use this IRQ attribute to tell KVM to update the > > > > related IRTE according the VT-d Posted-Interrrupts Specification, > > > > such as, the guest vector should be updated in the related IRTE. > > > > > > > > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx> > > > > --- > > > > Documentation/virtual/kvm/devices/vfio.txt | 9 +++++++++ > > > > include/uapi/linux/kvm.h | 10 ++++++++++ > > > > 2 files changed, 19 insertions(+), 0 deletions(-) > > > > > > > > diff --git a/Documentation/virtual/kvm/devices/vfio.txt > > > b/Documentation/virtual/kvm/devices/vfio.txt > > > > index f7aff29..41e12b7 100644 > > > > --- a/Documentation/virtual/kvm/devices/vfio.txt > > > > +++ b/Documentation/virtual/kvm/devices/vfio.txt > > > > @@ -42,3 +42,12 @@ activated before VFIO_DEVICE_SET_IRQS has been > > > called to trigger the IRQ > > > > or associate an eventfd to it. Unforwarding can only be called while the > > > > signaling has been disabled with VFIO_DEVICE_SET_IRQS. If this > condition > > > is > > > > not satisfied, the command returns an -EBUSY. > > > > + > > > > + KVM_DEV_VFIO_DEVICE_POSTING_IRQ: Use posted interrtups > > > mechanism to post > > > typo > > > > + the IRQ to guests. > > > > +For this attribute, kvm_device_attr.addr points to a kvm_vfio_dev_irq > > > struct. > > > > + > > > > +When guest OS changes the interrupt configuration for an assigned > device, > > > > +such as, MSI/MSIx data/address fields, QEMU will use this IRQ attribute > > > > +to tell KVM to update the related IRTE according the VT-d > > > Posted-Interrrupts > > > > +Specification, such as, the guest vector should be updated in the related > > > IRTE. > > > For my curiosity are there any restrictions about the instant at which > > > the change can be done? > > > I do not get here how you deactivate the posting? > > > > The current method is if the hardware supports interrupts posting, we will > > use it instead of interrupts remapping, since it has good performance. Why > > do I need deactivate interrupts posting? > > > > Here is the reply to Alex for the same question: > > "In fact, I don't think we need to stop the posted-interrupts. For setting > > posted interrupts, we update the related IRTE according to the new > > format. If the guest reboots, or unload the drivers, or some other > > operations, the msi/msix will be disabled first, in this path, the irq > > will be disabled the related IRTE is not used anymore." > > Right, and I'm still not sure I agree with that reasoning. We need to > build the kernel interface to be generic, not tailored for a specific > userspace. I don't really feel comfortable having something that can't > be disabled via a similar path to it being enabled. For instance, what > about a dynamic debug interface where we want to enable tracing and see > each interrupt injected into the guest. At that point we'd want to > disabled posted interrupts and direct KVM injection and route via QEMU. > Thanks, > > Alex Okay, I will think about this. Thanks, Feng > > > > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > > > > index a269a42..7d98650 100644 > > > > --- a/include/uapi/linux/kvm.h > > > > +++ b/include/uapi/linux/kvm.h > > > > @@ -949,6 +949,7 @@ struct kvm_device_attr { > > > > #define KVM_DEV_VFIO_DEVICE 2 > > > > #define KVM_DEV_VFIO_DEVICE_FORWARD_IRQ 1 > > > > #define KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ 2 > > > > +#define KVM_DEV_VFIO_DEVICE_POSTING_IRQ 3 > > > Maybe we should align our naming verb vs verbing here? > > > Best Regards > > > Eric > > > > No problem, I will align my patch in the next version. Thanks! > > > > Thanks, > > Feng > > > > > > > > > > enum kvm_device_type { > > > > KVM_DEV_TYPE_FSL_MPIC_20 = 1, > > > > @@ -973,6 +974,15 @@ struct kvm_arch_forwarded_irq { > > > > __u32 gsi; /* gsi, ie. virtual IRQ number */ > > > > }; > > > > > > > > +struct kvm_vfio_dev_irq { > > > > + __u32 argsz; > > > > + __u32 fd; /* file descriptor of the VFIO device */ > > > > + __u32 index; /* VFIO device IRQ index */ > > > > + __u32 start; > > > > + __u32 count; > > > > + __u32 gsi[]; /* gsi, ie. virtual IRQ number */ > > > > +}; > > > > + > > > > /* > > > > * ioctls for VM fds > > > > */ > > > > > > > > > > -- > > > To unsubscribe from this list: send the line "unsubscribe kvm" in > > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- > > To unsubscribe from this list: send the line "unsubscribe kvm" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > ��.n��������+%������w��{.n�����o�^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
