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

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Date:   Tue, 14 Mar 2023 08:15:22 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     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, 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>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v6 4/7] iommu/sva: Stop using ioasid_set for SVA

Hi Baolu,

On Tue, 14 Mar 2023 10:16:41 +0800, Baolu Lu <baolu.lu@...ux.intel.com>
wrote:

> 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:
> 
Got it :) I misunderstood, I thought you meant should not change to
pasid_valid()
will fix
> 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
> 


Thanks,

Jacob