linux-kernel - Re: [PATCH v3 1/7] iommu/amd: Warn when found inconsistency EFR mask

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Message-ID: <8b58ba70-714b-ac53-4598-a6c9f270a0be@amd.com>
Date:   Wed, 29 Jun 2022 18:50:46 +0700
From:   "Suthikulpanit, Suravee" <suravee.suthikulpanit@....com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        robin.murphy@....com, ashish.kalra@....com, vasant.hegde@....com,
        thomas.lendacky@....com
Subject: Re: [PATCH v3 1/7] iommu/amd: Warn when found inconsistency EFR mask



On 6/23/2022 3:22 PM, Joerg Roedel wrote:
> On Wed, Jun 22, 2022 at 12:11:25PM -0500, Suravee Suthikulpanit wrote:
>>   #ifdef CONFIG_IRQ_REMAP
>> +/*
>> + * Iterate through all the IOMMUs to verify if the specified
>> + * EFR bitmask of IOMMU feature are set.
>> + * Warn and return false if found inconsistency.
>> + */
>>   static bool check_feature_on_all_iommus(u64 mask)
>>   {
>>   	bool ret = false;
>>   	struct amd_iommu *iommu;
>>   
>>   	for_each_iommu(iommu) {
>> -		ret = iommu_feature(iommu, mask);
>> -		if (!ret)
>> +		bool tmp = iommu_feature(iommu, mask);
>> +
>> +		if ((ret != tmp) &&
>> +		    !list_is_first(&iommu->list, &amd_iommu_list)) {
>> +			pr_err(FW_BUG "Found inconsistent EFR mask (%#llx) on iommu%d (%04x:%02x:%02x.%01x).\n",
>> +			       mask, iommu->index, iommu->pci_seg->id, PCI_BUS_NUM(iommu->devid),
>> +			       PCI_SLOT(iommu->devid), PCI_FUNC(iommu->devid));
>>   			return false;
>> +		}
>> +		ret = tmp;
> 
> It is better to implement this by introducing a global feature mask,
> which represents the minial set of features supported by any IOMMU in
> the system.
> 
> The warning is then something like:
> 
> 	if ((global_feature_mask & iommu_features) != global_feature_mask)
> 		pr_warn(...);
> 
> This also makes the global variable to track SNP support obsolete.
> 
> Regards,
> 
> 	Joerg

That's actually better. I'll send out v4 w/ global EFR variable.

Thanks,
Suravee