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Tsirkin" To: Angus Chen Cc: "linux-kernel@vger.kernel.org" , Linus Torvalds , Michael Ellerman , Jason Wang , "virtualization@lists.linux-foundation.org" Subject: Re: [PATCH] virtio_pci: use irq to detect interrupt support Message-ID: <20221014013156-mutt-send-email-mst@kernel.org> References: <20221012220312.308522-1-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 14, 2022 at 12:09:20AM +0000, Angus Chen wrote: > Hi Mst > > > -----Original Message----- > > From: Michael S. Tsirkin > > Sent: Thursday, October 13, 2022 6:04 AM > > To: linux-kernel@vger.kernel.org > > Cc: Linus Torvalds ; Michael Ellerman > > ; Angus Chen ; Jason > > Wang ; virtualization@lists.linux-foundation.org > > Subject: [PATCH] virtio_pci: use irq to detect interrupt support > > > > commit 71491c54eafa ("virtio_pci: don't try to use intxif pin is zero") > > breaks virtio_pci on powerpc, when running as a qemu guest. > > > > vp_find_vqs() bails out because pci_dev->pin == 0. > > > > But pci_dev->irq is populated correctly, so vp_find_vqs_intx() would > > succeed if we called it - which is what the code used to do. > > > > This seems to happen because pci_dev->pin is not populated in > > pci_assign_irq(). > > > > Which is absolutely a bug in the relevant PCI code, but it > > may also affect other platforms that use of_irq_parse_and_map_pci(). > > > > However Linus said: > > The correct way to check for "no irq" doesn't use NO_IRQ at all, it just does > > if (dev->irq) ... > > so let's just check irq and be done with it. > > > > Suggested-by: Linus Torvalds > > Reported-by: Michael Ellerman > > Fixes: 71491c54eafa ("virtio_pci: don't try to use intxif pin is zero") > > Cc: "Angus Chen" > > Signed-off-by: Michael S. Tsirkin > > --- > > > > Build tested only - very late here. Angus any chance you could > > help test this? Thanks! > I tested the patch ，it work well on x86。Inlcude legacy and modern driver. > And I tested it on arm server also，and find some problem because of 0.9.5 limitation. > "platform bug: legacy virtio-pci must not be used with RAM above 0x%llxGB\n", > But the error is not effected by our patch.with or without our patch ,it print the same. Yes that's a limitation of 0.9.5 - just make a smaller VM to test legacy. > And I test modern dirver,it work well also. > Sorry for the late reply. Great, thanks a lot! > > > > drivers/virtio/virtio_pci_common.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/virtio/virtio_pci_common.c > > b/drivers/virtio/virtio_pci_common.c > > index 4df77eeb4d16..a6c86f916dbd 100644 > > --- a/drivers/virtio/virtio_pci_common.c > > +++ b/drivers/virtio/virtio_pci_common.c > > @@ -409,8 +409,8 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned int > > nvqs, > > err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, false, ctx, desc); > > if (!err) > > return 0; > > - /* Is there an interrupt pin? If not give up. */ > > - if (!(to_vp_device(vdev)->pci_dev->pin)) > > + /* Is there an interrupt? If not give up. */ > > + if (!(to_vp_device(vdev)->pci_dev->irq)) > > return err; > > /* Finally fall back to regular interrupts. */ > > return vp_find_vqs_intx(vdev, nvqs, vqs, callbacks, names, ctx); > > -- > > MST >