> -----Original Message----- > From: Marc Zyngier [mailto:maz@xxxxxxxxxx] > Sent: 25 January 2021 14:49 > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Bjorn > Helgaas <bhelgaas@xxxxxxxxxx>; stable@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] genirq/msi: Activate Multi-MSI early when > MSI_FLAG_ACTIVATE_EARLY is set > > On 2021-01-25 14:39, Shameerali Kolothum Thodi wrote: > >> -----Original Message----- > >> From: Marc Zyngier [mailto:maz@xxxxxxxxxx] > >> Sent: 23 January 2021 12:28 > >> To: linux-kernel@xxxxxxxxxxxxxxx > >> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Bjorn Helgaas > >> <bhelgaas@xxxxxxxxxx>; Shameerali Kolothum Thodi > >> <shameerali.kolothum.thodi@xxxxxxxxxx>; stable@xxxxxxxxxxxxxxx > >> Subject: [PATCH] genirq/msi: Activate Multi-MSI early when > >> MSI_FLAG_ACTIVATE_EARLY is set > >> > >> When MSI_FLAG_ACTIVATE_EARLY is set (which is the case for PCI), > >> we perform the activation of the interrupt (which in the case of > >> PCI results in the endpoint being programmed) as soon as the > >> interrupt is allocated. > >> > >> But it appears that this is only done for the first vector, > >> introducing an inconsistent behaviour for PCI Multi-MSI. > >> > >> Fix it by iterating over the number of vectors allocated to > >> each MSI descriptor. This is easily achieved by introducing > >> a new "for_each_msi_vector" iterator, together with a tiny > >> bit of refactoring. > >> > >> Fixes: f3b0946d629c ("genirq/msi: Make sure PCI MSIs are activated > >> early") > >> Reported-by: Shameer Kolothum > <shameerali.kolothum.thodi@xxxxxxxxxx> > >> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> > >> Cc: stable@xxxxxxxxxxxxxxx > >> --- > >> include/linux/msi.h | 6 ++++++ > >> kernel/irq/msi.c | 44 ++++++++++++++++++++------------------------ > >> 2 files changed, 26 insertions(+), 24 deletions(-) > >> > >> diff --git a/include/linux/msi.h b/include/linux/msi.h > >> index 360a0a7e7341..aef35fd1cf11 100644 > >> --- a/include/linux/msi.h > >> +++ b/include/linux/msi.h > >> @@ -178,6 +178,12 @@ struct msi_desc { > >> list_for_each_entry((desc), dev_to_msi_list((dev)), list) > >> #define for_each_msi_entry_safe(desc, tmp, dev) \ > >> list_for_each_entry_safe((desc), (tmp), dev_to_msi_list((dev)), > >> list) > >> +#define for_each_msi_vector(desc, __irq, dev) \ > >> + for_each_msi_entry((desc), (dev)) \ > >> + if ((desc)->irq) \ > >> + for (__irq = (desc)->irq; \ > >> + __irq < ((desc)->irq + (desc)->nvec_used); \ > >> + __irq++) > >> > >> #ifdef CONFIG_IRQ_MSI_IOMMU > >> static inline const void *msi_desc_get_iommu_cookie(struct msi_desc > >> *desc) > >> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c > >> index 2c0c4d6d0f83..d924676c8781 100644 > >> --- a/kernel/irq/msi.c > >> +++ b/kernel/irq/msi.c > >> @@ -436,22 +436,22 @@ int __msi_domain_alloc_irqs(struct irq_domain > >> *domain, struct device *dev, > >> > >> can_reserve = msi_check_reservation_mode(domain, info, dev); > >> > >> - for_each_msi_entry(desc, dev) { > >> - virq = desc->irq; > >> - if (desc->nvec_used == 1) > >> - dev_dbg(dev, "irq %d for MSI\n", virq); > >> - else > >> + /* > >> + * This flag is set by the PCI layer as we need to activate > >> + * the MSI entries before the PCI layer enables MSI in the > >> + * card. Otherwise the card latches a random msi message. > >> + */ > >> + if (!(info->flags & MSI_FLAG_ACTIVATE_EARLY)) > >> + goto skip_activate; > > > > This will change the dbg print behavior. From the commit f3b0946d629c, > > it looks like the below dev_dbg() code was there for > > !MSI_FLAG_ACTIVATE_EARLY > > case as well. Not sure how much this matters though. > > I'm not sure this matters either. We may have relied on these statements > some 6/7 years ago, as the whole hierarchy stuff was brand new, but we > now have a much better debug infrastructure thanks to Thomas. I'd be > totally in favour of dropping it. > Ok. Tested on D06 with gicv4 enabled and Guest MSI dev works fine. FWIW, Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx> Thanks, Shameer
