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Date:   Wed, 16 Nov 2022 09:39:32 -0800
From:   Ashok Raj <ashok.raj@intel.com>
To:     Thomas Gleixner <tglx@linutronix.de>
CC:     LKML <linux-kernel@vger.kernel.org>, <x86@kernel.org>,
        Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        <linux-pci@vger.kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
        "Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        Jason Gunthorpe <jgg@mellanox.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Kevin Tian <kevin.tian@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
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        Jon Mason <jdmason@kudzu.us>, Allen Hubbe <allenbh@gmail.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        <linuxppc-dev@lists.ozlabs.org>,
        "Ahmed S. Darwish" <darwi@linutronix.de>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Ashok Raj <ashok.raj@intel.com>
Subject: Re: [patch 02/39] iommu/vt-d: Remove bogus check for multi MSI-X
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On Wed, Nov 16, 2022 at 06:02:30PM +0100, Thomas Gleixner wrote:
> On Wed, Nov 16 2022 at 07:52, Ashok Raj wrote:
> > On Fri, Nov 11, 2022 at 02:54:17PM +0100, Thomas Gleixner wrote:
> >> PCI/Multi-MSI is MSI specific and not supported for MSI-X.
> >> 
> >> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> >> ---
> >>  drivers/iommu/intel/irq_remapping.c |    3 +--
> >>  1 file changed, 1 insertion(+), 2 deletions(-)
> >> 
> >> --- a/drivers/iommu/intel/irq_remapping.c
> >> +++ b/drivers/iommu/intel/irq_remapping.c
> >> @@ -1334,8 +1334,7 @@ static int intel_irq_remapping_alloc(str
> >>  
> >>  	if (!info || !iommu)
> >>  		return -EINVAL;
> >> -	if (nr_irqs > 1 && info->type != X86_IRQ_ALLOC_TYPE_PCI_MSI &&
> >> -	    info->type != X86_IRQ_ALLOC_TYPE_PCI_MSIX)
> >> +	if (nr_irqs > 1 && info->type != X86_IRQ_ALLOC_TYPE_PCI_MSI)
> >>  		return -EINVAL;
> >>  
> >>  	/*
> >> 
> >
> > This check is only making sure that when multi-msi is requested that the
> > type has to be either MSI/MSIX.
> 
> MSI-X does not support multi vector allocations on a single entry.
> 
> > Wouldn't this change return -EINVAL when type = MSIX?
> 
> Rightfully so. MSIX vectors are allocated one by one. Has been that way
> forever.
> 

I thought why block multi-vector allocation on MSIX, but if there is no
use case makes perfect sense.

Thanks for the clarification.

Reviewed-by: Ashok Raj <ashok.raj@intel.com>