[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH] xen/arm: smmuv1: remove iommu group when deassign a device
On 29/04/2022 15:33, Rahul Singh wrote: Hi Julien, Hi Rahul, On 27 Apr 2022, at 6:42 pm, Julien Grall <julien@xxxxxxx> wrote: Hi, On 27/04/2022 17:15, Rahul Singh wrote:When a device is deassigned from the domain it is required to remove the iommu group.This read wrong to me. We should not need to re-create the IOMMU group (and call arm_smmu_add_device()) every time a device is re-assigned.Ok.If we don't remove the group, the next time when we assign a device, SME and S2CR will not be setup correctly for the device because of that SMMU fault will be observed.I think this is a bug fix for 0435784cc75dcfef3b5f59c29deb1dbb84265ddb. If so, please add a Fixes tag.Ok Let me add the Fixes tag in next version.Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx> --- xen/drivers/passthrough/arm/smmu.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/xen/drivers/passthrough/arm/smmu.c b/xen/drivers/passthrough/arm/smmu.c index 5cacb2dd99..9a31c332d0 100644 --- a/xen/drivers/passthrough/arm/smmu.c +++ b/xen/drivers/passthrough/arm/smmu.c @@ -1690,6 +1690,8 @@ static void arm_smmu_detach_dev(struct iommu_domain *domain, struct device *dev) if (cfg) arm_smmu_master_free_smes(cfg); + iommu_group_put(dev_iommu_group(dev)); + dev_iommu_group(dev) = NULL; }The goal of arm_smmu_detach_dev() is to revert the change made in arm_smmu_attach_dev(). But looking at the code, neither the IOMMU group nor the smes are allocated in arm_smmu_attach_dev(). Are the SMES meant to be re-allocated everytime we assign to a different domain? If yes, the allocation should be done in arm_smmu_attach_dev().Yes SMES have to be re-allocated every time a device is assigned. Hmmmm.... Looking at the code, arm_smmu_alloc_smes() doesn't seem to use the domain information. So why would it need to be done every time it is assigned? Is that okay if I will move the function arm_smmu_master_alloc_smes() from arm_smmu_add_device() to arm_smmu_attach_dev(). In this case we don’t need to remove the IOMMU group and also arm_smmu_detach_dev() will also revert the change made in arm_smmu_attach_dev(). diff --git a/xen/drivers/passthrough/arm/smmu.c b/xen/drivers/passthrough/arm/smmu.c index 5cacb2dd99..ff1b73d3d8 100644 --- a/xen/drivers/passthrough/arm/smmu.c +++ b/xen/drivers/passthrough/arm/smmu.c @@ -1680,6 +1680,10 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev) if (!cfg) return -ENODEV;+ ret = arm_smmu_master_alloc_smes(dev);+ if (ret) + return ret; + return arm_smmu_domain_add_master(smmu_domain, cfg); If we go down this route, then you will likely need to revert the change made by arm_smmu_master_alloc_smes(). }@@ -2075,7 +2079,7 @@ static int arm_smmu_add_device(struct device *dev)iommu_group_add_device(group, dev); iommu_group_put(group);- return arm_smmu_master_alloc_smes(dev);+ return 0; } Regards, RahulIf not, then we should not free the SMES here IIUC, the SMES have to be re-allocated every time a device is assigned. Therefore, I think we should move the call to arm_smmu_master_alloc_smes() out of the detach callback and in a helper that would be used when removing a device (not yet supported by Xen). Cheers, -- Julien Grall -- Julien Grall
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