linux-kernel - Re: [PATCH v6 4/7] iommu/sva: Stop using ioasid

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Date:   Tue, 14 Mar 2023 10:16:41 +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>,
        Robin Murphy <robin.murphy@....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, 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>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH v6 4/7] iommu/sva: Stop using ioasid_set for SVA

On 3/14/23 4:41 AM, 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>
> ---
> v5:
> 	- Put removing iommu_sva_find() to a separate patch (Kevin)
> 	- Make pasid allocation range to be inclusive (Tina)
> 	- Simplified return code handling (Baolu)
> v4:
> 	- Keep GFP_ATOMIC flag for PASID allocation, will changed to
> 	GFP_KERNEL in a separate patch.
> ---
>   drivers/iommu/iommu-sva.c | 43 ++++++++++++++-------------------------
>   drivers/iommu/iommu-sva.h |  2 --
>   2 files changed, 15 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> index 4f357ef14f04..d4640731727a 100644
> --- a/drivers/iommu/iommu-sva.c
> +++ b/drivers/iommu/iommu-sva.c
> @@ -9,47 +9,34 @@
>   #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)
> +/* Allocate a PASID for the mm within range (inclusive) */
> +static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
>   {
>   	int ret = 0;
> -	ioasid_t pasid;
>   
> -	if (min == INVALID_IOASID || max == INVALID_IOASID ||
> -	    min == 0 || max < min)
> +	if (!pasid_valid(min) || !pasid_valid(max) ||
> +	     min == 0 || max < min)

I still think the last line change is unnecessary. Otherwise, you
probably will get below CHECK warning:

CHECK: Alignment should match open parenthesis
#259: FILE: drivers/iommu/iommu-sva.c:20:
+	if (!pasid_valid(min) || !pasid_valid(max) ||
+	     min == 0 || max < min)

Besides that,

Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>

Best regards,
baolu