Hi Jean, > -----Original Message----- > From: Jean-Philippe Brucker [mailto:jean-philippe@xxxxxxxxxx] > Sent: 04 March 2021 17:11 > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; > kvmarm@xxxxxxxxxxxxxxxxxxxxx; maz@xxxxxxxxxx; > alex.williamson@xxxxxxxxxx; eric.auger@xxxxxxxxxx; > zhangfei.gao@xxxxxxxxxx; Jonathan Cameron > <jonathan.cameron@xxxxxxxxxx>; Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>; > linuxarm@xxxxxxxxxxxxx > Subject: Re: [RFC PATCH 4/5] iommu/arm-smmu-v3: Use pinned VMID for > NESTED stage with BTM > > Hi Shameer, > > On Mon, Feb 22, 2021 at 03:53:37PM +0000, Shameer Kolothum wrote: > > If the SMMU supports BTM and the device belongs to NESTED domain > > with shared pasid table, we need to use the VMID allocated by the > > KVM for the s2 configuration. Hence, request a pinned VMID from KVM. > > > > Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx> > > --- > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 49 > ++++++++++++++++++++- > > 1 file changed, 47 insertions(+), 2 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 26bf7da1bcd0..04f83f7c8319 100644 > > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > @@ -28,6 +28,7 @@ > > #include <linux/pci.h> > > #include <linux/pci-ats.h> > > #include <linux/platform_device.h> > > +#include <linux/kvm_host.h> > > > > #include <linux/amba/bus.h> > > > > @@ -2195,6 +2196,33 @@ static void arm_smmu_bitmap_free(unsigned > long *map, int idx) > > clear_bit(idx, map); > > } > > > > +static int arm_smmu_pinned_vmid_get(struct arm_smmu_domain > *smmu_domain) > > +{ > > + struct arm_smmu_master *master; > > + > > + master = list_first_entry_or_null(&smmu_domain->devices, > > + struct arm_smmu_master, domain_head); > > This probably needs to hold devices_lock while using master. Ok. > > > + if (!master) > > + return -EINVAL; > > + > > + return kvm_pinned_vmid_get(master->dev); > > +} > > + > > +static int arm_smmu_pinned_vmid_put(struct arm_smmu_domain > *smmu_domain) > > +{ > > + struct arm_smmu_master *master; > > + > > + master = list_first_entry_or_null(&smmu_domain->devices, > > + struct arm_smmu_master, domain_head); > > + if (!master) > > + return -EINVAL; > > + > > + if (smmu_domain->s2_cfg.vmid) > > + return kvm_pinned_vmid_put(master->dev); > > + > > + return 0; > > +} > > + > > static void arm_smmu_domain_free(struct iommu_domain *domain) > > { > > struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain); > > @@ -2215,8 +2243,11 @@ static void arm_smmu_domain_free(struct > iommu_domain *domain) > > mutex_unlock(&arm_smmu_asid_lock); > > } > > if (s2_cfg->set) { > > - if (s2_cfg->vmid) > > - arm_smmu_bitmap_free(smmu->vmid_map, s2_cfg->vmid); > > + if (s2_cfg->vmid) { > > + if (!(smmu->features & ARM_SMMU_FEAT_BTM) && > > + smmu_domain->stage != ARM_SMMU_DOMAIN_NESTED) > > + arm_smmu_bitmap_free(smmu->vmid_map, > s2_cfg->vmid); > > + } > > } > > > > kfree(smmu_domain); > > @@ -3199,6 +3230,17 @@ static int arm_smmu_attach_pasid_table(struct > iommu_domain *domain, > > !(smmu->features & ARM_SMMU_FEAT_2_LVL_CDTAB)) > > goto out; > > > > + if (smmu->features & ARM_SMMU_FEAT_BTM) { > > + ret = arm_smmu_pinned_vmid_get(smmu_domain); > > + if (ret < 0) > > + goto out; > > + > > + if (smmu_domain->s2_cfg.vmid) > > + arm_smmu_bitmap_free(smmu->vmid_map, > smmu_domain->s2_cfg.vmid); > > + > > + smmu_domain->s2_cfg.vmid = (u16)ret; > > That will require a TLB invalidation on the old VMID, once the STE is > rewritten. True. Will add that. > More generally I think this pinned VMID set conflicts with that of > stage-2-only domains (which is the default state until a guest attaches a > PASID table). Say you have one guest using DOMAIN_NESTED without PASID > table, just DMA to IPA using VMID 0x8000. Now another guest attaches a > PASID table and obtains the same VMID from KVM. The stage-2 translation > might use TLB entries from the other guest, no? They'll both create > stage-2 TLB entries with {StreamWorld=NS-EL1, VMID=0x8000} > > It's tempting to allocate all VMIDs through KVM instead, but that will > force a dependency on KVM to use VFIO_TYPE1_NESTING_IOMMU and might > break > existing users of that extension (though I'm not sure there are any). > Instead we might need to restrict the SMMU VMID bitmap to match the > private VMID set in KVM. Right, that is indeed a problem. I will take a look at this suggestion. > Besides we probably want to restrict this feature to systems supporting > VMID16 on both SMMU and CPUs, or at least check that they are compatible. Yes. Ideally I would like to detect that in the KVM code and enable/disable the VMID splitting based on that. But I am yet to figure out an easy way to do that in KVM. > > + } > > + > > 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; > > @@ -3221,6 +3263,7 @@ static int arm_smmu_attach_pasid_table(struct > iommu_domain *domain, > > static void arm_smmu_detach_pasid_table(struct iommu_domain > *domain) > > { > > struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain); > > + struct arm_smmu_device *smmu = smmu_domain->smmu; > > struct arm_smmu_master *master; > > unsigned long flags; > > > > @@ -3237,6 +3280,8 @@ static void arm_smmu_detach_pasid_table(struct > iommu_domain *domain) > > arm_smmu_install_ste_for_dev(master); > > spin_unlock_irqrestore(&smmu_domain->devices_lock, flags); > > > > + if (smmu->features & ARM_SMMU_FEAT_BTM) > > + arm_smmu_pinned_vmid_put(smmu_domain); > > Aliasing here as well: the VMID is still live but can be reallocated by > KVM and another domain might obtain it. Ok. Got it. Thanks for the review, Shameer > > Thanks, > Jean > > > unlock: > > mutex_unlock(&smmu_domain->init_mutex); > > } > > -- > > 2.17.1 > > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
