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Date: Wed, 30 Oct 2013 10:20:40 +0800 From: Zhenzhong Duan <zhenzhong.duan@...cle.com> To: Bjorn Helgaas <bhelgaas@...gle.com> CC: "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, xen-devel <xen-devel@...ts.xen.org>, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, Feng Jin <joe.jin@...cle.com>, Sucheta Chakraborty <sucheta.chakraborty@...gic.com>, Jingoo Han <jg1.han@...sung.com> Subject: Re: [PATCH 2/3] PCI: Refactor MSI/MSIX mask restore code to fix interrupt lost issue On 2013-10-30 05:58, Bjorn Helgaas wrote: > On Wed, Oct 16, 2013 at 02:33:04PM +0800, Zhenzhong Duan wrote: >> Driver init call graph under baremetal: >> driver_init-> >> msix_capability_init-> >> msix_program_entries-> >> msix_mask_irq-> >> entry->masked = 1 >> request_irq-> >> __setup_irq-> >> irq_startup-> >> unmask_msi_irq-> >> msix_mask_irq-> >> entry->masked = 0; >> >> So entry->masked is always updated with newest value and its value could be used >> to restore to mask register in device. >> >> But in initial domain (aka priviliged guest), it's different. >> Driver init call graph under initial domain: >> driver_init-> >> msix_capability_init-> >> msix_program_entries-> >> msix_mask_irq-> >> entry->masked = 1 >> request_irq-> >> __setup_irq-> >> irq_startup-> >> __startup_pirq-> >> EVTCHNOP_bind_pirq hypercall (trap into Xen) >> [Xen:] >> pirq_guest_bind-> >> startup_msi_irq-> >> unmask_msi_irq-> >> msi_set_mask_bit-> >> entry->msi_attrib.masked = 0; The right mask value is saved in entry->msi_attrib.masked on Xen. >> >> So entry->msi_attrib.masked in xen side always has newest value. entry->masked >> in initial domain is untouched and is 1 after msix_capability_init. > If we run the following sequence: > > pci_enable_msix() > request_irq() > > don't we end up with the MSI IRQ unmasked if we're on bare metal but masked > if we're on Xen? It seems like we'd want it unmasked in both cases, so I > expected your patch to do something to make it unmasked if we're on Xen. > But I don't think it does, does it? > > As far as I can tell, this patch only changes the pci_restore_state() > path. I think that part makes sense. > > Bjorn It's unmasked on Xen too. This is just what this patch try to fix. In PHYSDEVOP_restore_msi hypercall, xen did the right thing that did by kernel in baremetal. > >> Based on above, it's Xen's duty to restore entry->msi_attrib.masked to device, >> but with current code, entry->masked is used and MSI-x interrupt is masked. >> >> Before patch, restore call graph under initial domain: >> pci_reset_function-> >> pci_restore_state-> >> __pci_restore_msix_state-> >> arch_restore_msi_irqs-> >> xen_initdom_restore_msi_irqs-> >> PHYSDEVOP_restore_msi hypercall (first mask restore) >> msix_mask_irq(entry, entry->masked) (second mask restore) >> >> So msix_mask_irq call in initial domain call graph needs to be removed. >> >> Based on this we can move the restore of the mask in default_restore_msi_irqs >> which would avoid restoring the invalid mask under Xen. Furthermore this >> simplifies the API by making everything related to restoring an MSI be in the >> platform specific APIs instead of just parts of it. >> >> After patch, restore call graph under initial domain: >> pci_reset_function-> >> pci_restore_state-> >> __pci_restore_msix_state-> >> arch_restore_msi_irqs-> >> xen_initdom_restore_msi_irqs-> >> PHYSDEVOP_restore_msi hypercall (first mask restore) and entry->msi_attrib.masked is restored to hardware register in PHYSDEVOP_restore_msi hypercall on Xen. >> >> Logic for baremetal is not changed. >> Before patch, restore call graph under baremetal: >> pci_reset_function-> >> pci_restore_state-> >> __pci_restore_msix_state-> >> arch_restore_msi_irqs-> >> default_restore_msi_irqs-> >> msix_mask_irq(entry, entry->masked) (first mask restore) >> >> After patch, restore call graph under baremetal: >> pci_reset_function-> >> pci_restore_state-> >> __pci_restore_msix_state-> >> arch_restore_msi_irqs-> >> default_restore_msi_irqs-> >> msix_mask_irq(entry, entry->masked) (first mask restore) >> >> The process for MSI code is similiar. >> >> Tested-by: Sucheta Chakraborty <sucheta.chakraborty@...gic.com> >> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...cle.com> >> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> >> --- >> drivers/pci/msi.c | 17 ++++++++++++++--- >> 1 files changed, 14 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c >> index ecd4cdf..38237f4 100644 >> --- a/drivers/pci/msi.c >> +++ b/drivers/pci/msi.c >> @@ -236,6 +236,8 @@ void unmask_msi_irq(struct irq_data *data) >> >> void default_restore_msi_irqs(struct pci_dev *dev, int irq) >> { >> + int pos; >> + u16 control; >> struct msi_desc *entry; >> >> entry = NULL; >> @@ -248,8 +250,19 @@ void default_restore_msi_irqs(struct pci_dev *dev, int irq) >> entry = irq_get_msi_desc(irq); >> } >> >> - if (entry) >> + if (entry) { >> write_msi_msg(irq, &entry->msg); >> + if (dev->msix_enabled) { >> + msix_mask_irq(entry, entry->masked); >> + readl(entry->mask_base); >> + } else { >> + pos = entry->msi_attrib.pos; >> + pci_read_config_word(dev, pos + PCI_MSI_FLAGS, >> + &control); >> + msi_mask_irq(entry, msi_capable_mask(control), >> + entry->masked); >> + } >> + } >> } >> >> void __read_msi_msg(struct msi_desc *entry, struct msi_msg *msg) >> @@ -423,7 +436,6 @@ static void __pci_restore_msi_state(struct pci_dev *dev) >> arch_restore_msi_irqs(dev, dev->irq); >> >> pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control); >> - msi_mask_irq(entry, msi_capable_mask(control), entry->masked); >> control &= ~PCI_MSI_FLAGS_QSIZE; >> control |= (entry->msi_attrib.multiple << 4) | PCI_MSI_FLAGS_ENABLE; >> pci_write_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, control); >> @@ -447,7 +459,6 @@ static void __pci_restore_msix_state(struct pci_dev *dev) >> >> list_for_each_entry(entry, &dev->msi_list, list) { >> arch_restore_msi_irqs(dev, entry->irq); >> - msix_mask_irq(entry, entry->masked); >> } >> >> control &= ~PCI_MSIX_FLAGS_MASKALL; >> -- >> 1.7.3 >> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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