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: <304df156-0374-4e43-b261-754b438e937b@amd.com>
Date: Fri, 11 Apr 2025 22:32:15 +0530
From: Sairaj Kodilkar <sarunkod@....com>
To: Sean Christopherson <seanjc@...gle.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 4/11/2025 7:35 PM, Sean Christopherson wrote:
> 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().
> 

Ohh sorry about that. Since I was reviewing patches sequentially, I did
come across those changes.

Regards
Sairaj Kodilkar

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