Re: [PATCH RESEND v9 09/13] iommu/arm-smmu-v3: Seize private ASID

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

On Mon, Sep 07, 2020 at 06:41:11PM +0200, Auger Eric wrote:
> > +/*
> > + * Try to reserve this ASID in the SMMU. If it is in use, try to steal it from
> > + * the private entry. Careful here, we may be modifying the context tables of
> > + * another SMMU!
> Not sure I got what you meant by this comment.

That comment does need refreshing:

/*
 * Check if the CPU ASID is available on the SMMU side. If a private context
 * descriptor is using it, try to replace it.
 */

> > + */
> >  static struct arm_smmu_ctx_desc *
> >  arm_smmu_share_asid(struct mm_struct *mm, u16 asid)
> >  {
> > +	int ret;
> > +	u32 new_asid;
> >  	struct arm_smmu_ctx_desc *cd;
> > +	struct arm_smmu_device *smmu;
> > +	struct arm_smmu_domain *smmu_domain;
> >  
> >  	cd = xa_load(&arm_smmu_asid_xa, asid);
> >  	if (!cd)
> > @@ -27,8 +36,31 @@ arm_smmu_share_asid(struct mm_struct *mm, u16 asid)
> >  		return cd;
> >  	}
> >  
> > -	/* Ouch, ASID is already in use for a private cd. */
> > -	return ERR_PTR(-EBUSY);
> > +	smmu_domain = container_of(cd, struct arm_smmu_domain, s1_cfg.cd);
> > +	smmu = smmu_domain->smmu;
> > +
> > +	ret = xa_alloc(&arm_smmu_asid_xa, &new_asid, cd,
> > +		       XA_LIMIT(1, 1 << smmu->asid_bits), GFP_KERNEL);
> XA_LIMIT(1, (1 << smmu->asid_bits) - 1), GFP_KERNEL)

Good catch

Thanks,
Jean

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