linux-kernel - Re: [PATCH V10 04/11] iommu/vt-d: Use helper function to skip agaw for SL

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Date:   Fri, 27 Mar 2020 17:05:52 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>
Cc:     "Liu, Yi L" <yi.l.liu@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH V10 04/11] iommu/vt-d: Use helper function to skip agaw
 for SL

Hi Jacob,

On 3/27/20 12:55 PM, Tian, Kevin wrote:
>> From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>> Sent: Saturday, March 21, 2020 7:28 AM
>>
>> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>> ---
>>  drivers/iommu/intel-pasid.c | 14 ++++----------
>>  1 file changed, 4 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/iommu/intel-pasid.c b/drivers/iommu/intel-pasid.c
>> index 191508c7c03e..9bdb7ee228b6 100644
>> --- a/drivers/iommu/intel-pasid.c
>> +++ b/drivers/iommu/intel-pasid.c
>> @@ -544,17 +544,11 @@ int intel_pasid_setup_second_level(struct
>> intel_iommu *iommu,
>>  		return -EINVAL;
>>  	}
>>
>> -	/*
>> -	 * Skip top levels of page tables for iommu which has less agaw
>> -	 * than default. Unnecessary for PT mode.
>> -	 */
>>  	pgd = domain->pgd;
>> -	for (agaw = domain->agaw; agaw > iommu->agaw; agaw--) {
>> -		pgd = phys_to_virt(dma_pte_addr(pgd));
>> -		if (!dma_pte_present(pgd)) {
>> -			dev_err(dev, "Invalid domain page table\n");
>> -			return -EINVAL;
>> -		}
>> +	agaw = iommu_skip_agaw(domain, iommu, &pgd);
>> +	if (agaw < 0) {
>> +		dev_err(dev, "Invalid domain page table\n");
is the dev_err() really requested. I see in domain_setup_first_level(),
there is none.
>> +		return -EINVAL;
>>  	}
> 
> ok, I see how it is used. possibly combine last and this one together since
> it's mostly moving code...

I tend to agree with Kevin. May be better squash the 2 patches. Also not
sure the inline of iommu_skip_agaw() is meaningful then. Also Add commit
messages on the resulting patch.

Note domain_setup_first_level() also could use the helper while we are
it (if declaration moved to common helper). Only the error code differs
in case !dma_pte_present(pgd), ie. -ENOMEM. May be good to align.

Otherwise those stuff may be done in a fixup patch.

Thanks

Eric
> 
>>
>>  	pgd_val = virt_to_phys(pgd);
>> --
>> 2.7.4
>