linux-kernel - Re: [PATCH 05/67] iommu/amd: Return an error if vCPU affinity is set for non-vCPU IRTE

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Message-ID: <Z_khsNAbh4kIhKVC@google.com>
Date: Fri, 11 Apr 2025 07:05:36 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sairaj Kodilkar <sarunkod@....com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Joerg Roedel <joro@...tes.org>, 
	David Woodhouse <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>, kvm@...r.kernel.org, 
	iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Maxim Levitsky <mlevitsk@...hat.com>, Joao Martins <joao.m.martins@...cle.com>, 
	David Matlack <dmatlack@...gle.com>, Vasant Hegde <vasant.hegde@....com>, 
	Naveen N Rao <naveen.rao@....com>, Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: Re: [PATCH 05/67] iommu/amd: Return an error if vCPU affinity is set
 for non-vCPU IRTE

On Fri, Apr 11, 2025, Sairaj Kodilkar wrote:
> On 4/5/2025 1:08 AM, Sean Christopherson wrote:
> > Return -EINVAL instead of success if amd_ir_set_vcpu_affinity() is
> > invoked without use_vapic; lying to KVM about whether or not the IRTE was
> > configured to post IRQs is all kinds of bad.
> > 
> > Fixes: d98de49a53e4 ("iommu/amd: Enable vAPIC interrupt remapping mode by default")
> > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > ---
> >   drivers/iommu/amd/iommu.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> > index cd5116d8c3b2..b3a01b7757ee 100644
> > --- a/drivers/iommu/amd/iommu.c
> > +++ b/drivers/iommu/amd/iommu.c
> > @@ -3850,7 +3850,7 @@ static int amd_ir_set_vcpu_affinity(struct irq_data *data, void *vcpu_info)
> >   	 * we should not modify the IRTE
> >   	 */
> >   	if (!dev_data || !dev_data->use_vapic)
> > -		return 0;
> > +		return -EINVAL;
> 
> Hi Sean,
> you can update following functions as well to return error when
> IOMMU is using legacy interrupt mode.
> 1. amd_iommu_update_ga
> 2. amd_iommu_activate_guest_mode
> 3. amd_iommu_deactivate_guest_mode

Heh, I'm well aware, and this series gets there eventually (the end product WARNs
and returns an error in all three functions).  I fixed amd_ir_set_vcpu_affinity()
early in the series because it's the initial API that KVM will use to configure
an IRTE for posting to a vCPU.  I.e. to reach the other helpers, KVM would need
to ignore the error returned by amd_ir_set_vcpu_affinity().

> Currently these functions return 0 to the kvm layer when they fail to
> set the IRTE.
> 
> Regards
> Sairaj Kodilkar