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Message-ID: <c34d66a1-1564-1ec5-86de-6ebd1ebb2f71@bell.net>
Date: Fri, 13 Jan 2023 03:15:00 -0500
From: Matt Fagnani <matt.fagnani@...l.net>
To: Lu Baolu <baolu.lu@...ux.intel.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Joerg Roedel <jroedel@...e.de>
Cc: Christian König <christian.koenig@....com>,
Jason Gunthorpe <jgg@...dia.com>,
Kevin Tian <kevin.tian@...el.com>,
Vasant Hegde <vasant.hegde@....com>,
Tony Zhu <tony.zhu@...el.com>, linux-pci@...r.kernel.org,
iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] PCI: Add translated request only flag for
pci_enable_pasid()
Baolu,
6.2-rc3 with v2 of this patch applied booted normally without the black
screen problem. regzbot by Thorsten Leemhuis recommends adding the
following link tag to the previous discussion at
https://linux-regtracking.leemhuis.info/regzbot/mainline/ "When fixing,
add this to the commit message to make regzbot notice patch postings and
commits to resolve the issue:" Link:
https://lore.kernel.org/r/15d0f9ff-2a56-b3e9-5b45-e6b23300ae3b@leemhuis.info/
Thanks,
Matt
On 1/12/23 20:44, Lu Baolu wrote:
> The PCIe fabric routes Memory Requests based on the TLP address, ignoring
> the PASID. In order to ensure system integrity, commit 201007ef707a ("PCI:
> Enable PASID only when ACS RR & UF enabled on upstream path") requires
> some ACS features being supported on device's upstream path when enabling
> PCI/PASID.
>
> One alternative is ATS which lets the device resolve the PASID+addr pair
> before a memory request is made into a routeable TLB address through the
> TA. Those resolved addresses are then cached on the device instead of
> in the IOMMU TLB and the device always sets the translated bit for PASID.
> One example of those devices are AMD graphic devices that always have ACS
> or ATS enabled together with PASID.
>
> This adds a flag parameter in the pci_enable_pasid() helper, with which
> the device driver could opt-in the fact that device always sets the
> translated bit for PASID.
>
> It also applies this opt-in for AMD graphic devices. Without this change,
> kernel boots to black screen on a system with below AMD graphic device:
>
> 00:01.0 VGA compatible controller: Advanced Micro Devices, Inc.
> [AMD/ATI] Wani [Radeon R5/R6/R7 Graphics] (rev ca)
> (prog-if 00 [VGA controller])
> DeviceName: ATI EG BROADWAY
> Subsystem: Hewlett-Packard Company Device 8332
>
> At present, it is a common practice to enable/disable PCI PASID in the
> iommu drivers. Considering that the device driver knows more about the
> specific device, we will follow up by moving pci_enable_pasid() into
> the specific device drivers.
>
> Fixes: 201007ef707a ("PCI: Enable PASID only when ACS RR & UF enabled on upstream path")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216865
> Reported-by: Matt Fagnani <matt.fagnani@...l.net>
> Suggested-by: Jason Gunthorpe <jgg@...dia.com>
> Suggested-by: Christian König <christian.koenig@....com>
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
> include/linux/pci-ats.h | 6 ++++--
> drivers/iommu/amd/iommu.c | 2 +-
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
> drivers/iommu/intel/iommu.c | 3 ++-
> drivers/pci/ats.c | 8 ++++++--
> 5 files changed, 14 insertions(+), 7 deletions(-)
>
> Change log:
> v2:
> - Convert the bool to a named flag;
> - Convert TRANSLED to XLATED.
>
> v1:
> - https://lore.kernel.org/linux-iommu/20230112084629.737653-1-baolu.lu@linux.intel.com/
>
> diff --git a/include/linux/pci-ats.h b/include/linux/pci-ats.h
> index df54cd5b15db..750fca736ef4 100644
> --- a/include/linux/pci-ats.h
> +++ b/include/linux/pci-ats.h
> @@ -4,6 +4,8 @@
>
> #include <linux/pci.h>
>
> +#define PCI_PASID_XLATED_REQ_ONLY BIT(0)
> +
> #ifdef CONFIG_PCI_ATS
> /* Address Translation Service */
> bool pci_ats_supported(struct pci_dev *dev);
> @@ -35,12 +37,12 @@ static inline bool pci_pri_supported(struct pci_dev *pdev)
> #endif /* CONFIG_PCI_PRI */
>
> #ifdef CONFIG_PCI_PASID
> -int pci_enable_pasid(struct pci_dev *pdev, int features);
> +int pci_enable_pasid(struct pci_dev *pdev, int features, int flags);
> void pci_disable_pasid(struct pci_dev *pdev);
> int pci_pasid_features(struct pci_dev *pdev);
> int pci_max_pasids(struct pci_dev *pdev);
> #else /* CONFIG_PCI_PASID */
> -static inline int pci_enable_pasid(struct pci_dev *pdev, int features)
> +static inline int pci_enable_pasid(struct pci_dev *pdev, int features, int flags)
> { return -EINVAL; }
> static inline void pci_disable_pasid(struct pci_dev *pdev) { }
> static inline int pci_pasid_features(struct pci_dev *pdev)
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index cbeaab55c0db..64a8c03d7dfa 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -1700,7 +1700,7 @@ static int pdev_pri_ats_enable(struct pci_dev *pdev)
> int ret;
>
> /* Only allow access to user-accessible pages */
> - ret = pci_enable_pasid(pdev, 0);
> + ret = pci_enable_pasid(pdev, 0, PCI_PASID_XLATED_REQ_ONLY);
> if (ret)
> goto out_err;
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index ab160198edd6..891bf53c45dc 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2350,7 +2350,7 @@ static int arm_smmu_enable_pasid(struct arm_smmu_master *master)
> if (num_pasids <= 0)
> return num_pasids;
>
> - ret = pci_enable_pasid(pdev, features);
> + ret = pci_enable_pasid(pdev, features, 0);
> if (ret) {
> dev_err(&pdev->dev, "Failed to enable PASID\n");
> return ret;
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 59df7e42fd53..5cc13f02a5ac 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1425,7 +1425,8 @@ static void iommu_enable_pci_caps(struct device_domain_info *info)
> undefined. So always enable PASID support on devices which
> have it, even if we can't yet know if we're ever going to
> use it. */
> - if (info->pasid_supported && !pci_enable_pasid(pdev, info->pasid_supported & ~1))
> + if (info->pasid_supported &&
> + !pci_enable_pasid(pdev, info->pasid_supported & ~1, 0))
> info->pasid_enabled = 1;
>
> if (info->pri_supported &&
> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> index f9cc2e10b676..3a2d9e0ba1d8 100644
> --- a/drivers/pci/ats.c
> +++ b/drivers/pci/ats.c
> @@ -353,12 +353,15 @@ void pci_pasid_init(struct pci_dev *pdev)
> * pci_enable_pasid - Enable the PASID capability
> * @pdev: PCI device structure
> * @features: Features to enable
> + * @flags: device-specific flags
> + * - PCI_PASID_XLATED_REQ_ONLY: The PCI device only issues PASID
> + * memory requests of translated type.
> *
> * Returns 0 on success, negative value on error. This function checks
> * whether the features are actually supported by the device and returns
> * an error if not.
> */
> -int pci_enable_pasid(struct pci_dev *pdev, int features)
> +int pci_enable_pasid(struct pci_dev *pdev, int features, int flags)
> {
> u16 control, supported;
> int pasid = pdev->pasid_cap;
> @@ -382,7 +385,8 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
> if (!pasid)
> return -EINVAL;
>
> - if (!pci_acs_path_enabled(pdev, NULL, PCI_ACS_RR | PCI_ACS_UF))
> + if (!(flags & PCI_PASID_XLATED_REQ_ONLY) &&
> + !pci_acs_path_enabled(pdev, NULL, PCI_ACS_RR | PCI_ACS_UF))
> return -EINVAL;
>
> pci_read_config_word(pdev, pasid + PCI_PASID_CAP, &supported);
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