linux-kernel - RE: [PATCH v1 1/4] iommu/arm-smmu-v3: Pass in vmid to arm_smmu_make_s2_domain

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Message-ID: <a95b39a55c324907a7001d3a2cdf076b@huawei.com>
Date: Wed, 5 Mar 2025 08:50:17 +0000
From: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
To: Nicolin Chen <nicolinc@...dia.com>, "will@...nel.org" <will@...nel.org>,
	"robin.murphy@....com" <robin.murphy@....com>, "jgg@...dia.com"
	<jgg@...dia.com>
CC: "joro@...tes.org" <joro@...tes.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "iommu@...ts.linux.dev"
	<iommu@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v1 1/4] iommu/arm-smmu-v3: Pass in vmid to
 arm_smmu_make_s2_domain_ste()

Hi Nicolin,

Thanks for sending out this series. This might as well help me to rework my pinned KVM
VMID series here,
https://lore.kernel.org/linux-iommu/20240208151837.35068-1-shameerali.kolothum.thodi@huawei.com/


> -----Original Message-----
> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Wednesday, March 5, 2025 5:04 AM
> To: will@...nel.org; robin.murphy@....com; jgg@...dia.com
> Cc: joro@...tes.org; linux-arm-kernel@...ts.infradead.org;
> iommu@...ts.linux.dev; linux-kernel@...r.kernel.org; Shameerali Kolothum
> Thodi <shameerali.kolothum.thodi@...wei.com>
> Subject: [PATCH v1 1/4] iommu/arm-smmu-v3: Pass in vmid to
> arm_smmu_make_s2_domain_ste()
> 
> An stage-2 STE requires a vmid that has been so far allocated per domain,
> so arm_smmu_make_s2_domain_ste() has been extracting the vmid from
> the S2
> domain.
> 
> To share an S2 parent domain across vSMMUs in the same VM, a vmid will
> be
> no longer allocated for nor stored in the S2 domain, but per vSMMU, which
> means the arm_smmu_make_s2_domain_ste() can get a vmid either from
> an S2
> domain (non nesting parent) or a vSMMU.
> 
> Allow to pass in vmid explicitly to arm_smmu_make_s2_domain_ste(),
> giving
> its callers a chance to pick the vmid between a domain or a vSMMU.
> 
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h         | 2 +-
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 6 ++++--
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-test.c    | 3 ++-
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c         | 6 +++---
>  4 files changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index bd9d7c85576a..e08c4ede4b2d 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -887,7 +887,7 @@ struct arm_smmu_entry_writer_ops {
>  void arm_smmu_make_abort_ste(struct arm_smmu_ste *target);
>  void arm_smmu_make_s2_domain_ste(struct arm_smmu_ste *target,
>  				 struct arm_smmu_master *master,
> -				 struct arm_smmu_domain *smmu_domain,
> +				 struct arm_smmu_domain *smmu_domain,
> u16 vmid,
>  				 bool ats_enabled);

Now that vmid is an input, do we need some kind of validation here as
at least vmid = 0 is reserved I guess for bypass STEs.

Thanks,
Shameer