From: Yi Sun <yi.y.sun@linux.intel.com>
To: Keqian Zhu <zhukeqian1@huawei.com>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
iommu@lists.linux-foundation.org,
Alex Williamson <alex.williamson@redhat.com>,
Robin Murphy <robin.murphy@arm.com>,
Will Deacon <will@kernel.org>,
Kirti Wankhede <kwankhede@nvidia.com>,
Cornelia Huck <cohuck@redhat.com>, Marc Zyngier <maz@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
wanghaibin.wang@huawei.com, jiangkunkun@huawei.com,
yuzenghui@huawei.com, lushenming@huawei.com
Subject: Re: [PATCH v2 04/11] iommu/arm-smmu-v3: Split block descriptor when start dirty log
Date: Wed, 17 Mar 2021 11:06:44 +0800 [thread overview]
Message-ID: <20210317030644.GO28580@yi.y.sun> (raw)
In-Reply-To: <84cef87c-af82-8564-fc23-654042448d05@huawei.com>
On 21-03-16 19:39:47, Keqian Zhu wrote:
> Hi Yi,
>
> On 2021/3/16 17:17, Yi Sun wrote:
> > On 21-03-10 17:06:07, Keqian Zhu wrote:
> >> From: jiangkunkun <jiangkunkun@huawei.com>
> >>
> >> Block descriptor is not a proper granule for dirty log tracking.
> >> Take an extreme example, if DMA writes one byte, under 1G mapping,
> >> the dirty amount reported to userspace is 1G, but under 4K mapping,
> >> the dirty amount is just 4K.
> >>
> >> This adds a new interface named start_dirty_log in iommu layer and
> >> arm smmuv3 implements it, which splits block descriptor to an span
> >> of page descriptors. Other types of IOMMU will perform architecture
> >> specific actions to start dirty log.
> >>
> >> To allow code reuse, the split_block operation is realized as an
> >> iommu_ops too. We flush all iotlbs after the whole procedure is
> >> completed to ease the pressure of iommu, as we will hanle a huge
> >> range of mapping in general.
> >>
> >> Spliting block does not simultaneously work with other pgtable ops,
> >> as the only designed user is vfio, which always hold a lock, so race
> >> condition is not considered in the pgtable ops.
> >>
> >> Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
> >> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
> >> ---
> >>
> >> changelog:
> >>
> >> v2:
> >> - Change the return type of split_block(). size_t -> int.
> >> - Change commit message to properly describe race condition. (Robin)
> >> - Change commit message to properly describe the need of split block.
> >> - Add a new interface named start_dirty_log(). (Sun Yi)
> >> - Change commit message to explain the realtionship of split_block() and start_dirty_log().
> >>
> >> ---
> >> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 52 +++++++++
> >> drivers/iommu/io-pgtable-arm.c | 122 ++++++++++++++++++++
> >> drivers/iommu/iommu.c | 48 ++++++++
> >> include/linux/io-pgtable.h | 2 +
> >> include/linux/iommu.h | 24 ++++
> >> 5 files changed, 248 insertions(+)
> >>
> > Could you please split iommu common interface to a separate patch?
> > This may make review and comments easier.
> Yup, good suggestion.
>
> >
> > IMHO, I think the start/stop interfaces could be merged into one, e.g:
> > int iommu_domain_set_hwdbm(struct iommu_domain *domain, bool enable,
> > unsigned long iova, size_t size,
> > int prot);
> Looks good, this reduces some code. but I have a concern that this causes loss of flexibility,
> as we must pass same arguments when start|stop dirty log. What's your opinion about this?
>
Per current design, start/stop interfaces have similar arguments. So I
think it is ok for now. For future extension, we may think to define a
structure to pass these arguments.
> >
> > Same comments to patch 5.
> OK. Thanks.
>
> >
> > BRs,
> > Yi Sun
> >
> >> --
> >> 2.19.1
> > .
> Thanks,
> Keqian
BRs,
Yi Sun
next prev parent reply other threads:[~2021-03-17 3:13 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-10 9:06 [PATCH v2 00/11] vfio/iommu_type1: Implement dirty log tracking based on smmuv3 HTTU Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 01/11] iommu/arm-smmu-v3: Add support for Hardware Translation Table Update Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 02/11] iommu/arm-smmu-v3: Enable HTTU for stage1 with io-pgtable mapping Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 03/11] iommu/arm-smmu-v3: Add feature detection for BBML Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 04/11] iommu/arm-smmu-v3: Split block descriptor when start dirty log Keqian Zhu
2021-03-16 9:17 ` Yi Sun
2021-03-16 11:39 ` Keqian Zhu
2021-03-17 3:06 ` Yi Sun [this message]
2021-03-10 9:06 ` [PATCH v2 05/11] iommu/arm-smmu-v3: Merge a span of page when stop " Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 06/11] iommu/arm-smmu-v3: Scan leaf TTD to sync hardware " Keqian Zhu
2021-03-17 10:44 ` Yi Sun
2021-03-17 12:59 ` Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 07/11] iommu/arm-smmu-v3: Clear dirty log according to bitmap Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 08/11] iommu/arm-smmu-v3: Add HWDBM device feature reporting Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 09/11] vfio/iommu_type1: Add HWDBM status maintanance Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 10/11] vfio/iommu_type1: Optimize dirty bitmap population based on iommu HWDBM Keqian Zhu
2021-03-10 9:06 ` [PATCH v2 11/11] vfio/iommu_type1: Add support for manual dirty log clear Keqian Zhu
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