Re: 回复: [PATCH v5] vp_vdpa: don't allocate unused msix vectors
On Tue, Apr 23, 2024 at 08:42:57AM +, Angus Chen wrote: > Hi mst. > > > -Original Message- > > From: Michael S. Tsirkin > > Sent: Tuesday, April 23, 2024 4:35 PM > > To: Gavin Liu > > Cc: jasow...@redhat.com; Angus Chen ; > > virtualizat...@lists.linux.dev; xuanz...@linux.alibaba.com; > > linux-kernel@vger.kernel.org; Heng Qi > > Subject: Re: 回复: [PATCH v5] vp_vdpa: don't allocate unused msix vectors > > > > On Tue, Apr 23, 2024 at 01:39:17AM +, Gavin Liu wrote: > > > On Wed, Apr 10, 2024 at 11:30:20AM +0800, lyx634449800 wrote: > > > > From: Yuxue Liu > > > > > > > > When there is a ctlq and it doesn't require interrupt callbacks,the > > > > original method of calculating vectors wastes hardware msi or msix > > > > resources as well as system IRQ resources. > > > > > > > > When conducting performance testing using testpmd in the guest os, it > > > > was found that the performance was lower compared to directly using > > > > vfio-pci to passthrough the device > > > > > > > > In scenarios where the virtio device in the guest os does not utilize > > > > interrupts, the vdpa driver still configures the hardware's msix > > > > vector. Therefore, the hardware still sends interrupts to the host os. > > > > > > >I just have a question on this part. How come hardware sends interrupts > > > >does > > not guest driver disable them? > > > > > >1：Assuming the guest OS's Virtio device is using PMD mode, QEMU sets > > the call fd to -1 > > >2：On the host side, the vhost_vdpa program will set > > vp_vdpa->vring[i].cb.callback to invalid > > >3：Before the modification, the vp_vdpa_request_irq function does not > > check whether > > > vp_vdpa->vring[i].cb.callback is valid. Instead, it enables the > > hardware's MSIX > > > interrupts based on the number of queues of the device > > > > > > > So MSIX is enabled but why would it trigger? virtio PMD in poll mode > > presumably suppresses interrupts after all. > Virtio pmd is in the guest,but in host side,the msix is enabled,then the > device will triger > Interrupt normally. I analysed this bug before,and I think gavin is right. > Did I make it clear? Not really. Guest disables interrupts presumably (it's polling) why does device still send them? > > > > > > > > > > > - Original Message - > > > From: Michael S. Tsirkin m...@redhat.com > > > Sent: April 22, 2024 20:09 > > > To: Gavin Liu gavin@jaguarmicro.com > > > Cc: jasow...@redhat.com; Angus Chen angus.c...@jaguarmicro.com; > > virtualizat...@lists.linux.dev; xuanz...@linux.alibaba.com; > > linux-kernel@vger.kernel.org; Heng Qi hen...@linux.alibaba.com > > > Subject: Re: [PATCH v5] vp_vdpa: don't allocate unused msix vectors > > > > > > > > > > > > External Mail: This email originated from OUTSIDE of the organization! > > > Do not click links, open attachments or provide ANY information unless you > > recognize the sender and know the content is safe. > > > > > > > > > On Wed, Apr 10, 2024 at 11:30:20AM +0800, lyx634449800 wrote: > > > > From: Yuxue Liu > > > > > > > > When there is a ctlq and it doesn't require interrupt callbacks,the > > > > original method of calculating vectors wastes hardware msi or msix > > > > resources as well as system IRQ resources. > > > > > > > > When conducting performance testing using testpmd in the guest os, it > > > > was found that the performance was lower compared to directly using > > > > vfio-pci to passthrough the device > > > > > > > > In scenarios where the virtio device in the guest os does not utilize > > > > interrupts, the vdpa driver still configures the hardware's msix > > > > vector. Therefore, the hardware still sends interrupts to the host os. > > > > > > I just have a question on this part. How come hardware sends interrupts > > > does > > not guest driver disable them? > > > > > > > Because of this unnecessary > > > > action by the hardware, hardware performance decreases, and it also > > > > affects the performance of the host os. > > > > > > > > Before modification:(interrupt mode) > > > > 32: 0 0 0 0 PCI-MSI 32768-edgevp-vdpa[:00:02.0]-0 > > > >
RE: 回复: [PATCH v5] vp_vdpa: don't allocate unused msix vectors
Hi mst. > -Original Message- > From: Michael S. Tsirkin > Sent: Tuesday, April 23, 2024 4:35 PM > To: Gavin Liu > Cc: jasow...@redhat.com; Angus Chen ; > virtualizat...@lists.linux.dev; xuanz...@linux.alibaba.com; > linux-kernel@vger.kernel.org; Heng Qi > Subject: Re: 回复: [PATCH v5] vp_vdpa: don't allocate unused msix vectors > > On Tue, Apr 23, 2024 at 01:39:17AM +, Gavin Liu wrote: > > On Wed, Apr 10, 2024 at 11:30:20AM +0800, lyx634449800 wrote: > > > From: Yuxue Liu > > > > > > When there is a ctlq and it doesn't require interrupt callbacks,the > > > original method of calculating vectors wastes hardware msi or msix > > > resources as well as system IRQ resources. > > > > > > When conducting performance testing using testpmd in the guest os, it > > > was found that the performance was lower compared to directly using > > > vfio-pci to passthrough the device > > > > > > In scenarios where the virtio device in the guest os does not utilize > > > interrupts, the vdpa driver still configures the hardware's msix > > > vector. Therefore, the hardware still sends interrupts to the host os. > > > > >I just have a question on this part. How come hardware sends interrupts > > >does > not guest driver disable them? > > > >1：Assuming the guest OS's Virtio device is using PMD mode, QEMU sets > the call fd to -1 > >2：On the host side, the vhost_vdpa program will set > vp_vdpa->vring[i].cb.callback to invalid > >3：Before the modification, the vp_vdpa_request_irq function does not > check whether > > vp_vdpa->vring[i].cb.callback is valid. Instead, it enables the > hardware's MSIX > > interrupts based on the number of queues of the device > > > > So MSIX is enabled but why would it trigger? virtio PMD in poll mode > presumably suppresses interrupts after all. Virtio pmd is in the guest,but in host side,the msix is enabled,then the device will triger Interrupt normally. I analysed this bug before,and I think gavin is right. Did I make it clear? > > > > > > > - Original Message - > > From: Michael S. Tsirkin m...@redhat.com > > Sent: April 22, 2024 20:09 > > To: Gavin Liu gavin@jaguarmicro.com > > Cc: jasow...@redhat.com; Angus Chen angus.c...@jaguarmicro.com; > virtualizat...@lists.linux.dev; xuanz...@linux.alibaba.com; > linux-kernel@vger.kernel.org; Heng Qi hen...@linux.alibaba.com > > Subject: Re: [PATCH v5] vp_vdpa: don't allocate unused msix vectors > > > > > > > > External Mail: This email originated from OUTSIDE of the organization! > > Do not click links, open attachments or provide ANY information unless you > recognize the sender and know the content is safe. > > > > > > On Wed, Apr 10, 2024 at 11:30:20AM +0800, lyx634449800 wrote: > > > From: Yuxue Liu > > > > > > When there is a ctlq and it doesn't require interrupt callbacks,the > > > original method of calculating vectors wastes hardware msi or msix > > > resources as well as system IRQ resources. > > > > > > When conducting performance testing using testpmd in the guest os, it > > > was found that the performance was lower compared to directly using > > > vfio-pci to passthrough the device > > > > > > In scenarios where the virtio device in the guest os does not utilize > > > interrupts, the vdpa driver still configures the hardware's msix > > > vector. Therefore, the hardware still sends interrupts to the host os. > > > > I just have a question on this part. How come hardware sends interrupts does > not guest driver disable them? > > > > > Because of this unnecessary > > > action by the hardware, hardware performance decreases, and it also > > > affects the performance of the host os. > > > > > > Before modification:(interrupt mode) > > > 32: 0 0 0 0 PCI-MSI 32768-edgevp-vdpa[:00:02.0]-0 > > > 33: 0 0 0 0 PCI-MSI 32769-edgevp-vdpa[:00:02.0]-1 > > > 34: 0 0 0 0 PCI-MSI 32770-edgevp-vdpa[:00:02.0]-2 > > > 35: 0 0 0 0 PCI-MSI 32771-edgevp-vdpa[:00:02.0]-config > > > > > > After modification:(interrupt mode) > > > 32: 0 0 1 7 PCI-MSI 32768-edge vp-vdpa[:00:02.0]-0 > > > 33: 36 0 3 0 PCI-MSI 32769-edge vp-vdpa[:00:02.0]-1 > > > 34: 0 0 0 0 PCI-MSI 32770-edge vp-vdpa[:00:02.0]-config > > > > > > Before modification:(virtio pmd mode for guest os) > > > 32: 0 0 0 0
Re: 回复: [PATCH v5] vp_vdpa: don't allocate unused msix vectors
On Tue, Apr 23, 2024 at 01:39:17AM +, Gavin Liu wrote: > On Wed, Apr 10, 2024 at 11:30:20AM +0800, lyx634449800 wrote: > > From: Yuxue Liu > > > > When there is a ctlq and it doesn't require interrupt callbacks,the > > original method of calculating vectors wastes hardware msi or msix > > resources as well as system IRQ resources. > > > > When conducting performance testing using testpmd in the guest os, it > > was found that the performance was lower compared to directly using > > vfio-pci to passthrough the device > > > > In scenarios where the virtio device in the guest os does not utilize > > interrupts, the vdpa driver still configures the hardware's msix > > vector. Therefore, the hardware still sends interrupts to the host os. > > >I just have a question on this part. How come hardware sends interrupts does > >not guest driver disable them? > >1：Assuming the guest OS's Virtio device is using PMD mode, QEMU sets the > call fd to -1 >2：On the host side, the vhost_vdpa program will set > vp_vdpa->vring[i].cb.callback to invalid >3：Before the modification, the vp_vdpa_request_irq function does not check > whether > vp_vdpa->vring[i].cb.callback is valid. Instead, it enables the > hardware's MSIX > interrupts based on the number of queues of the device > So MSIX is enabled but why would it trigger? virtio PMD in poll mode presumably suppresses interrupts after all. > > > - Original Message - > From: Michael S. Tsirkin m...@redhat.com > Sent: April 22, 2024 20:09 > To: Gavin Liu gavin@jaguarmicro.com > Cc: jasow...@redhat.com; Angus Chen angus.c...@jaguarmicro.com; > virtualizat...@lists.linux.dev; xuanz...@linux.alibaba.com; > linux-kernel@vger.kernel.org; Heng Qi hen...@linux.alibaba.com > Subject: Re: [PATCH v5] vp_vdpa: don't allocate unused msix vectors > > > > External Mail: This email originated from OUTSIDE of the organization! > Do not click links, open attachments or provide ANY information unless you > recognize the sender and know the content is safe. > > > On Wed, Apr 10, 2024 at 11:30:20AM +0800, lyx634449800 wrote: > > From: Yuxue Liu > > > > When there is a ctlq and it doesn't require interrupt callbacks,the > > original method of calculating vectors wastes hardware msi or msix > > resources as well as system IRQ resources. > > > > When conducting performance testing using testpmd in the guest os, it > > was found that the performance was lower compared to directly using > > vfio-pci to passthrough the device > > > > In scenarios where the virtio device in the guest os does not utilize > > interrupts, the vdpa driver still configures the hardware's msix > > vector. Therefore, the hardware still sends interrupts to the host os. > > I just have a question on this part. How come hardware sends interrupts does > not guest driver disable them? > > > Because of this unnecessary > > action by the hardware, hardware performance decreases, and it also > > affects the performance of the host os. > > > > Before modification:(interrupt mode) > > 32: 0 0 0 0 PCI-MSI 32768-edgevp-vdpa[:00:02.0]-0 > > 33: 0 0 0 0 PCI-MSI 32769-edgevp-vdpa[:00:02.0]-1 > > 34: 0 0 0 0 PCI-MSI 32770-edgevp-vdpa[:00:02.0]-2 > > 35: 0 0 0 0 PCI-MSI 32771-edgevp-vdpa[:00:02.0]-config > > > > After modification:(interrupt mode) > > 32: 0 0 1 7 PCI-MSI 32768-edge vp-vdpa[:00:02.0]-0 > > 33: 36 0 3 0 PCI-MSI 32769-edge vp-vdpa[:00:02.0]-1 > > 34: 0 0 0 0 PCI-MSI 32770-edge vp-vdpa[:00:02.0]-config > > > > Before modification:(virtio pmd mode for guest os) > > 32: 0 0 0 0 PCI-MSI 32768-edgevp-vdpa[:00:02.0]-0 > > 33: 0 0 0 0 PCI-MSI 32769-edgevp-vdpa[:00:02.0]-1 > > 34: 0 0 0 0 PCI-MSI 32770-edgevp-vdpa[:00:02.0]-2 > > 35: 0 0 0 0 PCI-MSI 32771-edgevp-vdpa[:00:02.0]-config > > > > After modification:(virtio pmd mode for guest os) > > 32: 0 0 0 0 PCI-MSI 32768-edge vp-vdpa[:00:02.0]-config > > > > To verify the use of the virtio PMD mode in the guest operating > > system, the following patch needs to be applied to QEMU: > > https://lore.kernel.org/all/20240408073311.2049-1-yuxue.liu@jaguarmicr > > o.com > > > > Signed-off-by: Yuxue Liu > > Acked-by: Jason Wang > > Reviewed-by: Heng Qi > > --- > > V5: modify the description of the printout when an exception occurs > > V4: update the title and assign values to uninitialized variables > > V3: delete unused variables and add validation records > > V2: fix when allocating IRQs, scan all queues > > > > drivers/vdpa/virtio_pci/vp_vdpa.c | 22 -- > > 1 file changed, 16 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/vdpa/virtio_pci/vp_vdpa.c > > b/drivers/vdpa/virtio_pci/vp_vdpa.c > > index df5f4a3bccb5..8de0224e9ec2 100644 > > --- a/drivers/vdpa/virtio_pci/vp_vdpa.c > > +++
