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From:   Zhangfei Gao <zhangfei.gao@linaro.org>
Date:   Tue, 16 May 2023 11:12:44 +0800
Message-ID: <CABQgh9FMGPnUpz6tc6c27i6nT0Lcs9YQMoO=V40Fi2inJiCh-A@mail.gmail.com>
Subject: Re: [PATCH v2 00/17] Add Nested Translation Support for SMMUv3
To:     Nicolin Chen <nicolinc@nvidia.com>
Cc:     jgg@nvidia.com, robin.murphy@arm.com, will@kernel.org,
        eric.auger@redhat.com, kevin.tian@intel.com,
        baolu.lu@linux.intel.com, joro@8bytes.org,
        shameerali.kolothum.thodi@huawei.com, jean-philippe@linaro.org,
        linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        alex.williamson@redhat.com, yi.l.liu@intel.com
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On Mon, 15 May 2023 at 23:58, Nicolin Chen <nicolinc@nvidia.com> wrote:
>
> Hi Zhangfei,
>
> On Mon, May 15, 2023 at 06:00:26PM +0800, Zhangfei Gao wrote:
>
> > I rebased on these two branches and did some basic tests.
> >
> > The basic functions work after backport
> > iommufd: Add IOMMU_PAGE_RESPONSE
> > iommufd: Add device fault handler support
> >
> > https://github.com/Linaro/linux-kernel-warpdrive/tree/uacce-devel-6.4
> > https://github.com/Linaro/qemu/tree/iommufd-6.4-nesting-smmuv3-v2
>
> Thanks for testing!
>
> > However when debugging hotplug PCI device, it still does not work,
> > Segmentation fault same as 6.2.
> >
> > guest kernel
> > CONFIG_HOTPLUG_PCI_PCIE=y
> >
> > boot guest (this info does not appear in 6.2)
> > qemu-system-aarch64: -device
> > vfio-pci,host=0000:76:00.1,bus=pci.1,addr=0x0,id=acc1,iommufd=iommufd0:
> > Failed to set data -1
> > qemu-system-aarch64: -device
> > vfio-pci,host=0000:76:00.1,bus=pci.1,addr=0x0,id=acc1,iommufd=iommufd0:
> > failed to set device data
>
> Hmm.. I wonder what fails the set_dev_data ioctl...
Simply debug, it is because dev_data.sid=0, causing
arm_smmu_set_dev_user_data fail

hw/arm/smmu-common.c
smmu_dev_set_iommu_device
.sid = smmu_get_sid(sdev)
smmu_dev_set_iommu_device dev_data.sid=0

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
arm_smmu_set_dev_user_data
u32 sid_user = user->sid;
if (!sid_user) return -EINVAL;

>
> > $ sudo nc -U /tmp/qmpm_1.socket
> > (qemu) info pci
> > (qemu) device_del acc1
> >
> > guest:
> > qemu-system-aarch64: IOMMU_IOAS_UNMAP failed: No such file or directory
> > qemu-system-aarch64: vfio_container_dma_unmap(0xaaaae1fc0380,
> > 0x8000000000, 0x10000) = -2 (No such file or directory)
>
From ex-email reply
(Eric) In qemu arm virt machine 0x8000000000 matches the PCI MMIO region.
(Yi) Currently, iommufd kernel part doesn't support mapping device BAR MMIO.
This is a known gap.

> This is resulted from the following commit that we should
> drop later:
>
> commit c4fd2efd7c02dd30491adf676c1b0aed67656f36
> Author: Yi Liu <yi.l.liu@intel.com>
> Date:   Thu Apr 27 05:47:03 2023 -0700
>
>     vfio/container: Skip readonly pages
>
>     This is a temparary solution for Intel platform due to an errata in
>     which readonly pages in second stage page table is exclusive with
>     nested support.
>
>     Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>
>
> > qemu-system-aarch64: Failed to unset data -1
> > Segmentation fault (core dumped).  // also happened in 6.2
>
> Hmm, would it be possible for you to run the test again by
> adding the following tracers to your QEMU command?
>     --trace "iommufd*" \
>     --trace "smmu*" \
>     --trace "vfio_*" \
>     --trace "pci_*"
>

Have sent you the log directly, since it is too big.

Thanks