linux-kernel - Re: [RFC PATCH 10/11] vfio/iommu_type1: Optimize dirty bitmap population based on iommu HWDBM

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Date:   Sun, 7 Feb 2021 18:40:36 +0800
From:   Keqian Zhu <zhukeqian1@...wei.com>
To:     Yi Sun <yi.y.sun@...ux.intel.com>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <kvm@...r.kernel.org>,
        <kvmarm@...ts.cs.columbia.edu>, <iommu@...ts.linux-foundation.org>,
        Will Deacon <will@...nel.org>,
        "Alex Williamson" <alex.williamson@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Kirti Wankhede <kwankhede@...dia.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Robin Murphy <robin.murphy@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        <wanghaibin.wang@...wei.com>, <jiangkunkun@...wei.com>,
        <yuzenghui@...wei.com>, <lushenming@...wei.com>,
        <kevin.tian@...el.com>, <yan.y.zhao@...el.com>,
        <baolu.lu@...ux.intel.com>
Subject: Re: [RFC PATCH 10/11] vfio/iommu_type1: Optimize dirty bitmap
 population based on iommu HWDBM

Hi Yi,

On 2021/2/7 17:56, Yi Sun wrote:
> Hi,
> 
> On 21-01-28 23:17:41, Keqian Zhu wrote:
> 
> [...]
> 
>> +static void vfio_dma_dirty_log_start(struct vfio_iommu *iommu,
>> +				     struct vfio_dma *dma)
>> +{
>> +	struct vfio_domain *d;
>> +
>> +	list_for_each_entry(d, &iommu->domain_list, next) {
>> +		/* Go through all domain anyway even if we fail */
>> +		iommu_split_block(d->domain, dma->iova, dma->size);
>> +	}
>> +}
> 
> This should be a switch to prepare for dirty log start. Per Intel
> Vtd spec, there is SLADE defined in Scalable-Mode PASID Table Entry.
> It enables Accessed/Dirty Flags in second-level paging entries.
> So, a generic iommu interface here is better. For Intel iommu, it
> enables SLADE. For ARM, it splits block.
Indeed, a generic interface name is better.

The vendor iommu driver plays vendor's specific actions to start dirty log, and Intel iommu and ARM smmu may differ. Besides, we may add more actions in ARM smmu driver in future.

One question: Though I am not familiar with Intel iommu, I think it also should split block mapping besides enable SLADE. Right?

Thanks,
Keqian