linux-kernel - Re: [PATCH v5 09/12] iommu: Make iommu_queue

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Message-ID: <e7c773f6-969c-0097-1bca-24d276e8a8f6@linux.intel.com>
Date:   Fri, 22 Sep 2023 10:44:45 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...pe.ca>,
        "Liu, Jingqi" <jingqi.liu@...el.com>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        iommu@...ts.linux.dev, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 09/12] iommu: Make iommu_queue_iopf() more generic



On 9/22/23 7:34 AM, Jason Gunthorpe wrote:
> On Thu, Sep 21, 2023 at 11:25:56PM +0800, Liu, Jingqi wrote:
>>
>> On 9/14/2023 4:56 PM, Lu Baolu wrote:
>>> Make iommu_queue_iopf() more generic by making the iopf_group a minimal
>>> set of iopf's that an iopf handler of domain should handle and respond
>>> to. Add domain parameter to struct iopf_group so that the handler can
>>> retrieve and use it directly.
>>>
>>> Change iommu_queue_iopf() to forward groups of iopf's to the domain's
>>> iopf handler. This is also a necessary step to decouple the sva iopf
>>> handling code from this interface.
>>>
>>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>>> ---
>>>    include/linux/iommu.h      |  4 ++--
>>>    drivers/iommu/iommu-sva.h  |  6 ++---
>>>    drivers/iommu/io-pgfault.c | 49 ++++++++++++++++++++++++++++----------
>>>    drivers/iommu/iommu-sva.c  |  3 +--
>>>    4 files changed, 42 insertions(+), 20 deletions(-)
>>>
>> ......
>>
>>> @@ -112,6 +110,7 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
>>>    {
>>>    	int ret;
>>>    	struct iopf_group *group;
>>> +	struct iommu_domain *domain;
>>>    	struct iopf_fault *iopf, *next;
>>>    	struct iommu_fault_param *iopf_param;
>>>    	struct dev_iommu *param = dev->iommu;
>>> @@ -143,6 +142,19 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
>>>    		return 0;
>>>    	}
>>> +	if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID)
>>> +		domain = iommu_get_domain_for_dev_pasid(dev, fault->prm.pasid, 0);
>>> +	else
>>> +		domain = iommu_get_domain_for_dev(dev);
>>> +
>>> +	if (!domain || !domain->iopf_handler) {
>>
>> Does it need to check if 'domain' is error ?  Like below:
>>
>>           if (!domain || IS_ERR(domain) || !domain->iopf_handler)
> 
> Urk, yes, but not like that
> 
> The IF needs to be moved into the else block as each individual
> function has its own return convention.

iommu_get_domain_for_dev_pasid() returns an ERR_PTR only if the matching
domain type is specified (non-zero).

Adding IS_ERR(domain) in the else block will make the code more
readable. Alternatively we can put a comment around above code to
explain that ERR_PTR is not a case here.

Best regards,
baolu