RE: [PATCH v14 13/13] iommu/smmuv3: Accept configs with more than one context descriptor

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

> -----Original Message-----
> From: Auger Eric [mailto:eric.auger@redhat.com]
> Sent: 01 April 2021 12:49
> To: yuzenghui <yuzenghui@huawei.com>
> Cc: eric.auger.pro@gmail.com; iommu@lists.linux-foundation.org;
> linux-kernel@vger.kernel.org; kvm@vger.kernel.org;
> kvmarm@lists.cs.columbia.edu; will@kernel.org; maz@kernel.org;
> robin.murphy@arm.com; joro@8bytes.org; alex.williamson@redhat.com;
> tn@semihalf.com; zhukeqian <zhukeqian1@huawei.com>;
> jacob.jun.pan@linux.intel.com; yi.l.liu@intel.com; wangxingang
> <wangxingang5@huawei.com>; jiangkunkun <jiangkunkun@huawei.com>;
> jean-philippe@linaro.org; zhangfei.gao@linaro.org; zhangfei.gao@gmail.com;
> vivek.gautam@arm.com; Shameerali Kolothum Thodi
> <shameerali.kolothum.thodi@huawei.com>; nicoleotsuka@gmail.com;
> lushenming <lushenming@huawei.com>; vsethi@nvidia.com; Wanghaibin (D)
> <wanghaibin.wang@huawei.com>
> Subject: Re: [PATCH v14 13/13] iommu/smmuv3: Accept configs with more than
> one context descriptor
> 
> Hi Zenghui,
> 
> On 3/30/21 11:23 AM, Zenghui Yu wrote:
> > Hi Eric,
> >
> > On 2021/2/24 4:56, Eric Auger wrote:
> >> In preparation for vSVA, let's accept userspace provided configs
> >> with more than one CD. We check the max CD against the host iommu
> >> capability and also the format (linear versus 2 level).
> >>
> >> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> >> Signed-off-by: Shameer Kolothum
> <shameerali.kolothum.thodi@huawei.com>
> >> ---
> >>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 13 ++++++++-----
> >>   1 file changed, 8 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> >> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> >> index 332d31c0680f..ab74a0289893 100644
> >> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> >> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> >> @@ -3038,14 +3038,17 @@ static int
> arm_smmu_attach_pasid_table(struct
> >> iommu_domain *domain,
> >>           if (smmu_domain->s1_cfg.set)
> >>               goto out;
> >>   -        /*
> >> -         * we currently support a single CD so s1fmt and s1dss
> >> -         * fields are also ignored
> >> -         */
> >> -        if (cfg->pasid_bits)
> >> +        list_for_each_entry(master, &smmu_domain->devices,
> >> domain_head) {
> >> +            if (cfg->pasid_bits > master->ssid_bits)
> >> +                goto out;
> >> +        }
> >> +        if (cfg->vendor_data.smmuv3.s1fmt ==
> >> STRTAB_STE_0_S1FMT_64K_L2 &&
> >> +                !(smmu->features &
> ARM_SMMU_FEAT_2_LVL_CDTAB))
> >>               goto out;
> >>             smmu_domain->s1_cfg.cdcfg.cdtab_dma = cfg->base_ptr;
> >> +        smmu_domain->s1_cfg.s1cdmax = cfg->pasid_bits;
> >> +        smmu_domain->s1_cfg.s1fmt =
> cfg->vendor_data.smmuv3.s1fmt;
> >
> > And what about the SIDSS field?
> >
> I added this patch upon Shameer's request, to be more vSVA friendly.
> Hower this series does not really target multiple CD support. At the
> moment the driver only supports STRTAB_STE_1_S1DSS_SSID0 (0x2) I think.
> At this moment maybe I can only check the s1dss field is 0x2. Or simply
> removes this patch?
> 
> Thoughts?

Right. This was useful for vSVA tests. But yes, to properly support multiple CDs
we need to pass the S1DSS from Qemu. And that requires further changes.
So I think it's better to remove this patch and reject S1CDMAX != 0 cases.

Thanks,
Shameer
   
> 
> Eric