Messages in this thread | | | Date | Mon, 25 Jan 2021 14:48:38 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH] genirq/msi: Activate Multi-MSI early when MSI_FLAG_ACTIVATE_EARLY is set |
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On 2021-01-25 14:39, Shameerali Kolothum Thodi wrote: >> -----Original Message----- >> From: Marc Zyngier [mailto:maz@kernel.org] >> Sent: 23 January 2021 12:28 >> To: linux-kernel@vger.kernel.org >> Cc: Thomas Gleixner <tglx@linutronix.de>; Bjorn Helgaas >> <bhelgaas@google.com>; Shameerali Kolothum Thodi >> <shameerali.kolothum.thodi@huawei.com>; stable@vger.kernel.org >> 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@huawei.com> >> Signed-off-by: Marc Zyngier <maz@kernel.org> >> Cc: stable@vger.kernel.org >> --- >> 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.
Thanks,
M. -- Jazz is not dead. It just smells funny...
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