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Message-ID: <3b7fb4d3-1fe9-a3be-46ad-c271be9f96c7@linux.intel.com>
Date: Thu, 2 Mar 2023 21:01:42 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Jacob Pan <jacob.jun.pan@...ux.intel.com>,
LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
Jason Gunthorpe <jgg@...dia.com>,
Joerg Roedel <joro@...tes.org>,
Jean-Philippe Brucker <jean-philippe@...aro.com>,
Dave Hansen <dave.hansen@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
X86 Kernel <x86@...nel.org>, bp@...en8.de,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>, corbet@....net,
vkoul@...nel.org, dmaengine@...r.kernel.org,
linux-doc@...r.kernel.org
Cc: baolu.lu@...ux.intel.com, Robin Murphy <robin.murphy@....com>,
Will Deacon <will@...nel.org>,
David Woodhouse <dwmw2@...radead.org>,
Raj Ashok <ashok.raj@...el.com>,
"Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
"Yu, Fenghua" <fenghua.yu@...el.com>,
Dave Jiang <dave.jiang@...el.com>,
Kirill Shutemov <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v4 3/6] iommu/sva: Stop using ioasid_set for SVA
On 2023/3/2 7:56, Jacob Pan wrote:
> From: Jason Gunthorpe <jgg@...dia.com>
>
> Instead SVA drivers can use a simple global IDA to allocate PASIDs for
> each mm_struct.
>
> Future work would be to allow drivers using the SVA APIs to reserve global
> PASIDs from this IDA for their internal use, eg with the DMA API PASID
> support.
>
> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
> v4:
> - Keep GFP_ATOMIC flag for PASID allocation, will changed to
> GFP_KERNEL in a separate patch.
> ---
> drivers/iommu/iommu-sva.c | 62 ++++++++++-----------------------------
> drivers/iommu/iommu-sva.h | 3 --
> 2 files changed, 15 insertions(+), 50 deletions(-)
>
> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> index 376b2a9e2543..297852ae5e7c 100644
> --- a/drivers/iommu/iommu-sva.c
> +++ b/drivers/iommu/iommu-sva.c
> @@ -9,26 +9,13 @@
> #include "iommu-sva.h"
>
> static DEFINE_MUTEX(iommu_sva_lock);
> -static DECLARE_IOASID_SET(iommu_sva_pasid);
> +static DEFINE_IDA(iommu_global_pasid_ida);
>
> -/**
> - * iommu_sva_alloc_pasid - Allocate a PASID for the mm
> - * @mm: the mm
> - * @min: minimum PASID value (inclusive)
> - * @max: maximum PASID value (inclusive)
> - *
> - * Try to allocate a PASID for this mm, or take a reference to the existing one
> - * provided it fits within the [@min, @max] range. On success the PASID is
> - * available in mm->pasid and will be available for the lifetime of the mm.
> - *
> - * Returns 0 on success and < 0 on error.
> - */
> -int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
> +static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
> {
> - int ret = 0;
> - ioasid_t pasid;
> + int ret;
>
> - if (min == INVALID_IOASID || max == INVALID_IOASID ||
> + if (min == IOMMU_PASID_INVALID || max == IOMMU_PASID_INVALID ||
> min == 0 || max < min)
It's irrelevant to this patch. Just out of curiosity, why do we need to
exclude PASID 0 here? I just had a quick look at PCI spec section 6.20.
The spec does not state that PASID 0 is invalid.
> return -EINVAL;
>
> @@ -37,39 +24,20 @@ int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
> if (pasid_valid(mm->pasid)) {
> if (mm->pasid < min || mm->pasid >= max)
> ret = -EOVERFLOW;
> + else
> + ret = 0;
Nit:
If you didn't change "int ret = 0" to "int ret", we don't need above two
lines. Did I miss anything?
> goto out;
> }
>
> - pasid = ioasid_alloc(&iommu_sva_pasid, min, max, mm);
> - if (!pasid_valid(pasid))
> - ret = -ENOMEM;
> - else
> - mm->pasid = ret;
> + ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_ATOMIC);
> + if (ret < min)
Nit:
ret < 0?
ida_alloc_range() returns negative error number on failure.
> + goto out;
> + mm->pasid = ret;
> + ret = 0;
> out:
> mutex_unlock(&iommu_sva_lock);
> return ret;
> }
> -EXPORT_SYMBOL_GPL(iommu_sva_alloc_pasid);
> -
> -/* ioasid_find getter() requires a void * argument */
> -static bool __mmget_not_zero(void *mm)
> -{
> - return mmget_not_zero(mm);
> -}
> -
> -/**
> - * iommu_sva_find() - Find mm associated to the given PASID
> - * @pasid: Process Address Space ID assigned to the mm
> - *
> - * On success a reference to the mm is taken, and must be released with mmput().
> - *
> - * Returns the mm corresponding to this PASID, or an error if not found.
> - */
> -struct mm_struct *iommu_sva_find(ioasid_t pasid)
> -{
> - return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
> -}
> -EXPORT_SYMBOL_GPL(iommu_sva_find);
Removing iommu_sva_find() has nothing to do with the intention of this
patch. Perhaps make it in a separated patch?
>
> /**
> * iommu_sva_bind_device() - Bind a process address space to a device
> @@ -241,8 +209,8 @@ iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
>
> void mm_pasid_drop(struct mm_struct *mm)
> {
> - if (pasid_valid(mm->pasid)) {
> - ioasid_free(mm->pasid);
> - mm->pasid = INVALID_IOASID;
> - }
> + if (likely(!pasid_valid(mm->pasid)))
Why is this a likely?
> + return;
> +
> + ida_free(&iommu_global_pasid_ida, mm->pasid);
> }
> diff --git a/drivers/iommu/iommu-sva.h b/drivers/iommu/iommu-sva.h
> index 7215a761b962..c22d0174ad61 100644
> --- a/drivers/iommu/iommu-sva.h
> +++ b/drivers/iommu/iommu-sva.h
> @@ -8,9 +8,6 @@
> #include <linux/ioasid.h>
> #include <linux/mm_types.h>
>
> -int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max);
> -struct mm_struct *iommu_sva_find(ioasid_t pasid);
> -
> /* I/O Page fault */
> struct device;
> struct iommu_fault;
Best regards,
baolu
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