From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:37882 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751141AbbCMDfs (ORCPT ); Thu, 12 Mar 2015 23:35:48 -0400 From: Bandan Das To: Fam Zheng Cc: linux-kernel@vger.kernel.org, Bjorn Helgaas , linux-pci@vger.kernel.org, Alex Williamson Subject: Re: [RFC PATCH] PCI: Disable MSI/MSI-X only if device is shutdown References: <1426137682-12287-1-git-send-email-famz@redhat.com> <20150313020919.GD32054@ad.nay.redhat.com> <20150313031757.GA26947@ad.nay.redhat.com> Date: Thu, 12 Mar 2015 23:35:45 -0400 In-Reply-To: <20150313031757.GA26947@ad.nay.redhat.com> (Fam Zheng's message of "Fri, 13 Mar 2015 11:17:57 +0800") Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-pci-owner@vger.kernel.org List-ID: Fam Zheng writes: > On Thu, 03/12 23:09, Bandan Das wrote: >> Ccing Alex, he can probably confirm if my understanding is indeed correct. >> >> Fam Zheng writes: >> >> > On Thu, 03/12 19:56, Bandan Das wrote: >> >> Hi Fam, >> >> >> >> Fam Zheng writes: >> >> >> >> > If the device doesn't support shutdown, disabling interrupts may cause >> >> > trouble. For example, virtio-scsi-pci doesn't implement shutdown, and >> >> > after we disable MSI-X, futher notifications from device will be >> >> > delivered to IRQ, which is unexpected. This IRQ will not be cleared, and >> >> > may prevent us from making progress, by keep triggering interrupts. >> >> > >> >> > Signed-off-by: Fam Zheng >> >> > --- >> >> > drivers/pci/pci-driver.c | 7 ++++--- >> >> > 1 file changed, 4 insertions(+), 3 deletions(-) >> >> > >> >> > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c >> >> > index 3cb2210..fb29c96 100644 >> >> > --- a/drivers/pci/pci-driver.c >> >> > +++ b/drivers/pci/pci-driver.c >> >> > @@ -448,10 +448,11 @@ static void pci_device_shutdown(struct device *dev) >> >> > >> >> > pm_runtime_resume(dev); >> >> > >> >> > - if (drv && drv->shutdown) >> >> > + if (drv && drv->shutdown) { >> >> > drv->shutdown(pci_dev); >> >> > - pci_msi_shutdown(pci_dev); >> >> > - pci_msix_shutdown(pci_dev); >> >> > + pci_msi_shutdown(pci_dev); >> >> > + pci_msix_shutdown(pci_dev); >> >> > + } >> >> >> >> If the driver doesn't provide a shutdown method and doesn't itself >> >> disable MSI/MSI-X, then pci_msi(x)_shutdown won't be called anymore, >> >> no ? >> > >> > Right. >> > >> >> >> >> This is probably ok (but unclean) for a system shutdown, but could >> >> cause problems for something like kexec ? >> > >> > Doesn't the reset in kexec clean this up during initialization? >> >> I guess it would take the same path as a reboot. > > I don't understand, do you mean that no reset will be done before more > operations on the device? I meant that it's upto the individual driver, pci will take the same path as a regular reboot. >> >> > Without shutdown, anything in the driver is unclean anyway, for example >> > free_irq is not called. >> >> True, And that is why the MSI/-X shutdown functions are called here >> because pci can't always rely on the individual device drivers to do >> the right thing, but atleast can make a best effort at cleaning up. > > This virtio-scsi case shows us that intermediate state is bad, so I still think > we should call pci_msix_shutdown conditionally. > > Fam