From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Keqian Zhu <zhukeqian1@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
"Tian, Kevin" <kevin.tian@intel.com>,
Cornelia Huck <cohuck@redhat.com>,
Alex Williamson <alex.williamson@redhat.com>,
kvm@vger.kernel.org, Suzuki K Poulose <suzuki.poulose@arm.com>,
Will Deacon <will@kernel.org>,
jiangkunkun@huawei.com, lushenming@huawei.com,
linux-kernel@vger.kernel.org,
Kirti Wankhede <kwankhede@nvidia.com>,
Catalin Marinas <catalin.marinas@arm.com>,
iommu@lists.linux-foundation.org,
James Morse <james.morse@arm.com>, Marc Zyngier <maz@kernel.org>,
wanghaibin.wang@huawei.com, Robin Murphy <robin.murphy@arm.com>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 01/11] iommu/arm-smmu-v3: Add feature detection for HTTU
Date: Fri, 5 Feb 2021 10:51:14 +0100 [thread overview]
Message-ID: <YB0VErwkA0ivRXTd@myrica> (raw)
In-Reply-To: <df1b8fb2-b853-e797-0072-9dbdffc4ff67@huawei.com>
Hi Keqian,
On Fri, Feb 05, 2021 at 05:13:50PM +0800, Keqian Zhu wrote:
> > We need to accommodate the firmware override as well if we need this to be meaningful. Jean-Philippe is already carrying a suitable patch in the SVA stack[1].
> Robin, Thanks for pointing it out.
>
> Jean, I see that the IORT HTTU flag overrides the hardware register info unconditionally. I have some concern about it:
>
> If the override flag has HTTU but hardware doesn't support it, then driver will use this feature but receive access fault or permission fault from SMMU unexpectedly.
> 1) If IOPF is not supported, then kernel can not work normally.
> 2) If IOPF is supported, kernel will perform useless actions, such as HTTU based dma dirty tracking (this series).
>
> As the IORT spec doesn't give an explicit explanation for HTTU override, can we comprehend it as a mask for HTTU related hardware register?
To me "Overrides the value of SMMU_IDR0.HTTU" is clear enough: disregard
the value of SMMU_IDR0.HTTU and use the one specified by IORT instead. And
that's both ways, since there is no validity mask for the IORT value: if
there is an IORT table, always ignore SMMU_IDR0.HTTU.
That's how the SMMU driver implements the COHACC bit, which has the same
wording in IORT. So I think we should implement HTTU the same way.
One complication is that there is no equivalent override for device tree.
I think it can be added later if necessary, because unlike IORT it can be
tri state (property not present, overriden positive, overridden negative).
Thanks,
Jean
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next prev parent reply other threads:[~2021-02-05 9:51 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-28 15:17 [RFC PATCH 00/11] vfio/iommu_type1: Implement dirty log tracking based on smmuv3 HTTU Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 01/11] iommu/arm-smmu-v3: Add feature detection for HTTU Keqian Zhu
2021-02-04 19:50 ` Robin Murphy
2021-02-05 9:13 ` Keqian Zhu
2021-02-05 9:51 ` Jean-Philippe Brucker [this message]
2021-02-07 1:42 ` Keqian Zhu
2021-02-05 11:48 ` Robin Murphy
2021-02-05 16:11 ` Robin Murphy
2021-02-07 1:56 ` Keqian Zhu
2021-02-07 2:19 ` Keqian Zhu
2021-03-02 7:42 ` Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 02/11] iommu/arm-smmu-v3: Enable HTTU for SMMU stage1 mapping Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 03/11] iommu/arm-smmu-v3: Add feature detection for BBML Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 04/11] iommu/arm-smmu-v3: Split block descriptor to a span of page Keqian Zhu
2021-02-04 19:51 ` Robin Murphy
2021-02-07 8:18 ` Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 05/11] iommu/arm-smmu-v3: Merge a span of page to block descriptor Keqian Zhu
2021-02-04 19:52 ` Robin Murphy
2021-02-07 12:13 ` Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 06/11] iommu/arm-smmu-v3: Scan leaf TTD to sync hardware dirty log Keqian Zhu
2021-02-04 19:52 ` Robin Murphy
2021-02-07 12:41 ` Keqian Zhu
2021-02-08 1:17 ` Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 07/11] iommu/arm-smmu-v3: Clear dirty log according to bitmap Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 08/11] iommu/arm-smmu-v3: Add HWDBM device feature reporting Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 09/11] vfio/iommu_type1: Add HWDBM status maintanance Keqian Zhu
2021-01-28 15:17 ` [RFC PATCH 10/11] vfio/iommu_type1: Optimize dirty bitmap population based on iommu HWDBM Keqian Zhu
2021-02-07 9:56 ` Yi Sun
2021-02-07 10:40 ` Keqian Zhu
2021-02-09 11:57 ` Yi Sun
2021-02-09 12:08 ` Robin Murphy
2021-02-10 6:15 ` zhukeqian
2021-02-18 1:17 ` Keqian Zhu
2021-02-09 11:16 ` Robin Murphy
2021-02-09 12:02 ` Yi Sun
2021-01-28 15:17 ` [RFC PATCH 11/11] vfio/iommu_type1: Add support for manual dirty log clear Keqian Zhu
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