Re: [PATCHv9 3/8] iommu/arm-smmu: Move non-strict mode to use io_pgtable_domain_attr

[Sai Prakash Ranjan]

On 2020-11-25 03:09, Will Deacon wrote:
> On Mon, Nov 23, 2020 at 10:35:56PM +0530, Sai Prakash Ranjan wrote:
> > Now that we have a struct io_pgtable_domain_attr with quirks,
> > use that for non_strict mode as well thereby removing the need
> > for more members of arm_smmu_domain in the future.
> >
> > Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
> > ---
> >  drivers/iommu/arm/arm-smmu/arm-smmu.c | 8 +++-----
> >  drivers/iommu/arm/arm-smmu/arm-smmu.h | 1 -
> >  2 files changed, 3 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c 
> > b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > index 4b9b10fe50ed..f56f266ebdf7 100644
> > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > @@ -786,9 +786,6 @@ static int arm_smmu_init_domain_context(struct 
> > iommu_domain *domain,
> >  			goto out_clear_smmu;
> >  	}
> >
> > -	if (smmu_domain->non_strict)
> > -		pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
> > -
> >  	if (smmu_domain->pgtbl_cfg.quirks)
> >  		pgtbl_cfg.quirks |= smmu_domain->pgtbl_cfg.quirks;
> >
> > @@ -1527,7 +1524,8 @@ static int arm_smmu_domain_get_attr(struct 
> > iommu_domain *domain,
> >  	case IOMMU_DOMAIN_DMA:
> >  		switch (attr) {
> >  		case DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE:
> > -			*(int *)data = smmu_domain->non_strict;
> > +			if (smmu_domain->pgtbl_cfg.quirks & IO_PGTABLE_QUIRK_NON_STRICT)
> > +				*(int *)data = smmu_domain->pgtbl_cfg.quirks;
>
> I still don't think this is right :(
> We need to set *data to 1 or 0 depending on whether or not the 
> non-strict
> quirk is set, i.e:
>
> 	bool non_strict = smmu_domain->pgtbl_cfg.quirks & 
> IO_PGTABLE_QUIRK_NON_STRICT;
> 	*(int *)data = non_strict;
>
> Your code above leaves *data uninitialised if non_strict is not set.

Ugh sorry, I should have looked at this some more before hurrying up
to post, will fix it.

> >  			return 0;
> >  		default:
> >  			return -ENODEV;
> > @@ -1578,7 +1576,7 @@ static int arm_smmu_domain_set_attr(struct 
> > iommu_domain *domain,
> >  	case IOMMU_DOMAIN_DMA:
> >  		switch (attr) {
> >  		case DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE:
> > -			smmu_domain->non_strict = *(int *)data;
> > +			smmu_domain->pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
>
> And this is broken because if *data is 0, then you _set_ the quirk, 
> which is
> the opposite of what we should be doing.
>
> In other words, although the implementation has changed, the semantics 
> have
> not.

Will fix this to have quirk set only when *data = 1 and unset in case of 
0.

Thanks,
Sai

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