[PATCH] genirq/msi: Make sure early activation of all PCI MSIs

[Shameerali Kolothum Thodi]

Hi Marc,

> -----Original Message-----
> From: Marc Zyngier [mailto:maz at kernel.org]
> Sent: 21 January 2021 21:25
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi at huawei.com>
> Cc: linux-kernel at vger.kernel.org; linux-arm-kernel at lists.infradead.org;
> eric.auger at redhat.com; tglx at linutronix.de; linuxarm at openeuler.org;
> Zengtao (B) <prime.zeng at hisilicon.com>; Wangzhou (B)
> <wangzhou1 at hisilicon.com>
> Subject: Re: [PATCH] genirq/msi: Make sure early activation of all PCI MSIs
> 
> Hi Shameer,
> 
> On Thu, 21 Jan 2021 11:02:47 +0000,
> Shameer Kolothum <shameerali.kolothum.thodi at huawei.com> wrote:
> >
> > We currently do early activation of MSI irqs for PCI/MSI based on the
> > MSI_FLAG_ACTIVATE_EARLY flag. Though this activates all the allocated
> > MSIs in the case of MSI-X, it only does so for the base irq in the
> > case of MSI. This is because, for MSI, there is only one msi_desc
> > entry for all the 32 irqs it can support and the current
> > implementation iterates over the msi entries and ends up activating
> > the base irq only.
> >
> > The above creates an issue on platforms where the msi controller
> > supports direct injection of vLPIs(eg: ARM GICv4 ITS). On these
> > platforms, upon irq activation, ITS driver maps the event to an ITT
> > entry. And for Guest pass-through to work, early mapping of all the
> > dev MSI vectors is required. Otherwise, the vfio irq bypass manager
> > registration will fail. eg, On a HiSilicon D06 platform with GICv4
> > enabled, Guest boot with zip dev pass-through reports,
> >
> > "vfio-pci 0000:75:00.1: irq bypass producer (token 0000000006e5176a)
> > registration fails: 66311"
> >
> > and Guest boot fails.
> >
> > This is traced to,
> >    kvm_arch_irq_bypass_add_producer
> >      kvm_vgic_v4_set_forwarding
> >        vgic_its_resolve_lpi --> returns
> E_ITS_INT_UNMAPPED_INTERRUPT
> >
> > Hence make sure we activate all the irqs for both MSI and MSI-x cases.
> >
> > Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
> > ---
> > It is unclear to me whether not performing the early activation of all
> > MSI irqs was deliberate and has consequences on any other platforms.
> > Please let me know.
> 
> Probably just an oversight.

Ok. That’s a good news :)

> >
> > Thanks,
> > Shameer
> > ---
> >  kernel/irq/msi.c | 114
> > +++++++++++++++++++++++++++++++++++++----------
> >  1 file changed, 90 insertions(+), 24 deletions(-)
> >
> > diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c index
> > 2c0c4d6d0f83..eec187fc32a9 100644
> > --- a/kernel/irq/msi.c
> > +++ b/kernel/irq/msi.c
> > @@ -395,6 +395,78 @@ static bool msi_check_reservation_mode(struct
> irq_domain *domain,
> >  	return desc->msi_attrib.is_msix || desc->msi_attrib.maskbit;  }
> >
> > +static void msi_domain_deactivate_irq(struct irq_domain *domain, int
> > +irq) {
> > +	struct irq_data *irqd;
> > +
> > +	irqd = irq_domain_get_irq_data(domain, irq);
> > +	if (irqd_is_activated(irqd))
> > +		irq_domain_deactivate_irq(irqd);
> > +}
> > +
> > +static int msi_domain_activate_irq(struct irq_domain *domain,
> > +				   int irq, bool can_reserve)
> > +{
> > +	struct irq_data *irqd;
> > +
> > +	irqd = irq_domain_get_irq_data(domain, irq);
> > +	if (!can_reserve) {
> > +		irqd_clr_can_reserve(irqd);
> > +		if (domain->flags & IRQ_DOMAIN_MSI_NOMASK_QUIRK)
> > +			irqd_set_msi_nomask_quirk(irqd);
> > +	}
> > +	return irq_domain_activate_irq(irqd, can_reserve); }
> > +
> > +static int msi_domain_activate_msix_irqs(struct irq_domain *domain,
> > +					 struct device *dev, bool can_reserve) {
> > +	struct msi_desc *desc;
> > +	int ret, irq;
> > +
> > +	for_each_msi_entry(desc, dev) {
> > +		irq = desc->irq;
> > +		ret = msi_domain_activate_irq(domain, irq, can_reserve);
> > +		if (ret)
> > +			goto out;
> > +	}
> > +	return 0;
> > +
> > +out:
> > +	for_each_msi_entry(desc, dev) {
> > +		if (irq == desc->irq)
> > +			break;
> > +		msi_domain_deactivate_irq(domain, desc->irq);
> > +	}
> > +	return ret;
> > +}
> > +
> > +static int msi_domain_activate_msi_irqs(struct irq_domain *domain,
> > +					struct device *dev, bool can_reserve) {
> > +	struct msi_desc *desc;
> > +	int i, ret, base, irq;
> > +
> > +	desc = first_msi_entry(dev);
> > +	base = desc->irq;
> > +
> > +	for (i = 0; i < desc->nvec_used; i++) {
> > +		irq = base + i;
> > +		ret = msi_domain_activate_irq(domain, irq, can_reserve);
> > +		if (ret)
> > +			goto out;
> > +	}
> > +	return 0;
> > +
> > +out:
> > +	for (i = 0; i < desc->nvec_used; i++) {
> > +		if (irq == base + i)
> > +			break;
> > +		msi_domain_deactivate_irq(domain, base + i);
> > +	}
> > +	return ret;
> > +}
> > +
> >  int __msi_domain_alloc_irqs(struct irq_domain *domain, struct device
> *dev,
> >  			    int nvec)
> >  {
> > @@ -443,21 +515,25 @@ int __msi_domain_alloc_irqs(struct irq_domain
> *domain, struct device *dev,
> >  		else
> >  			dev_dbg(dev, "irq [%d-%d] for MSI\n",
> >  				virq, virq + desc->nvec_used - 1);
> > -		/*
> > -		 * 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))
> > -			continue;
> > +	}
> >
> > -		irq_data = irq_domain_get_irq_data(domain, desc->irq);
> > -		if (!can_reserve) {
> > -			irqd_clr_can_reserve(irq_data);
> > -			if (domain->flags & IRQ_DOMAIN_MSI_NOMASK_QUIRK)
> > -				irqd_set_msi_nomask_quirk(irq_data);
> > -		}
> > -		ret = irq_domain_activate_irq(irq_data, can_reserve);
> > +	/*
> > +	 * 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.
> > +	 * Early activation is also required when the msi controller
> > +	 * supports direct injection of virtual LPIs(eg. ARM GICv4 ITS).
> > +	 * Otherwise, the DevID/EventID -> LPI translation for pass-through
> > +	 * devices will fail. Make sure we do activate all the allocated
> > +	 * irqs for MSI and MSI-X cases.
> > +	 */
> > +	if ((info->flags & MSI_FLAG_ACTIVATE_EARLY)) {
> > +		desc = first_msi_entry(dev);
> > +
> > +		if (desc->msi_attrib.is_msix)
> > +			ret = msi_domain_activate_msix_irqs(domain, dev,
> can_reserve);
> > +		else
> > +			ret = msi_domain_activate_msi_irqs(domain, dev, can_reserve);
> >  		if (ret)
> >  			goto cleanup;
> >  	}
> > @@ -475,16 +551,6 @@ int __msi_domain_alloc_irqs(struct irq_domain
> *domain, struct device *dev,
> >  	return 0;
> >
> >  cleanup:
> > -	for_each_msi_entry(desc, dev) {
> > -		struct irq_data *irqd;
> > -
> > -		if (desc->irq == virq)
> > -			break;
> > -
> > -		irqd = irq_domain_get_irq_data(domain, desc->irq);
> > -		if (irqd_is_activated(irqd))
> > -			irq_domain_deactivate_irq(irqd);
> > -	}
> >  	msi_domain_free_irqs(domain, dev);
> >  	return ret;
> >  }
> > --
> > 2.17.1
> >
> >
> 
> I find this pretty complicated, and the I'd like to avoid injecting the PCI
> MSI-vs-MSI-X concept in something that is supposed to be bus-agnostic.

Agree. That’s mainly because I was very skeptical(TBH, very limited in my knowledge
on this msi core code) about changing the MSI-X activation logic here and just thought
of limiting the impact to MSI case as a first attempt.

> What's wrong with the following (untested) patch, which looks much simpler?

Yes, had tried this as one of the early fix, but as said above was not very sure of
the impact on other platforms. Tested this again and it works.

Please send it.

Thanks,
Shameer

> Thanks,
> 
> 	M.
> 
> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c index
> 2c0c4d6d0f83..a930d03c2c67 100644
> --- a/kernel/irq/msi.c
> +++ b/kernel/irq/msi.c
> @@ -451,15 +451,17 @@ int __msi_domain_alloc_irqs(struct irq_domain
> *domain, struct device *dev,
>  		if (!(info->flags & MSI_FLAG_ACTIVATE_EARLY))
>  			continue;
> 
> -		irq_data = irq_domain_get_irq_data(domain, desc->irq);
> -		if (!can_reserve) {
> -			irqd_clr_can_reserve(irq_data);
> -			if (domain->flags & IRQ_DOMAIN_MSI_NOMASK_QUIRK)
> -				irqd_set_msi_nomask_quirk(irq_data);
> +		for (i = 0; i < desc->nvec_used; i++) {
> +			irq_data = irq_domain_get_irq_data(domain, desc->irq + i);
> +			if (!can_reserve) {
> +				irqd_clr_can_reserve(irq_data);
> +				if (domain->flags & IRQ_DOMAIN_MSI_NOMASK_QUIRK)
> +					irqd_set_msi_nomask_quirk(irq_data);
> +			}
> +			ret = irq_domain_activate_irq(irq_data, can_reserve);
> +			if (ret)
> +				goto cleanup;
>  		}
> -		ret = irq_domain_activate_irq(irq_data, can_reserve);
> -		if (ret)
> -			goto cleanup;
>  	}
> 
>  	/*
> @@ -478,12 +480,14 @@ int __msi_domain_alloc_irqs(struct irq_domain
> *domain, struct device *dev,
>  	for_each_msi_entry(desc, dev) {
>  		struct irq_data *irqd;
> 
> +		for (i = 0; i < desc->nvec_used; i++) {
> +			irqd = irq_domain_get_irq_data(domain, desc->irq + i);
> +			if (irqd_is_activated(irqd))
> +				irq_domain_deactivate_irq(irqd);
> +		}
> +
>  		if (desc->irq == virq)
>  			break;
> -
> -		irqd = irq_domain_get_irq_data(domain, desc->irq);
> -		if (irqd_is_activated(irqd))
> -			irq_domain_deactivate_irq(irqd);
>  	}
>  	msi_domain_free_irqs(domain, dev);
>  	return ret;
> 
> --
> Without deviation from the norm, progress is not possible.