Messages in this thread | | | Date | Tue, 7 Apr 2020 13:01:46 +0200 | From | Jean-Philippe Brucker <> | Subject | Re: [PATCH 05/10] iommu/ioasid: Create an IOASID set for host SVA use |
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On Mon, Apr 06, 2020 at 08:33:53AM -0700, Jacob Pan wrote: > Hi Jean, > > On Wed, 1 Apr 2020 15:53:16 +0200 > Jean-Philippe Brucker <jean-philippe@linaro.org> wrote: > > > On Wed, Mar 25, 2020 at 10:55:26AM -0700, Jacob Pan wrote: > > > Bare metal SVA allocates IOASIDs for native process addresses. This > > > should be separated from VM allocated IOASIDs thus under its own > > > set. > > > > > > This patch creates a system IOASID set with its quota set to > > > PID_MAX. This is a reasonable default in that SVM capable devices > > > can only bind to limited user processes. > > > > Yes realistically there won't be more than PID_MAX_DEFAULT=0x8000 > > bound address spaces. My machine uses a PID_MAX of 4 million though, > > so in theory more than 0x8000 processes may want a bond. > Got it, I assume we can adjust the system set quota as necessary. > > > On Arm the > > limit of shared contexts per VM is currently a little less than > > 0x10000 (which is the number of CPU ASIDs). > > > I guess shared contexts means shared address? then it makes sense > #IOASID < #ASID.
Yes by shared contexts I mean shared address spaces. Theoretically #ASID < #IOASID for us, because the max ASID size is 16-bit.
> > > But quotas are only necessary for VMs, when the host shares the PASID > > space with them (which isn't a use-case for Arm systems as far as I > > know, each VM gets its own PASID space). > Is there a host-guest PASID translation? or the PASID used by the VM is > physical PASID? When a page request comes in to SMMU, how does it know > the owner of the PASID if PASID range can overlap between host and > guest?
We assign PCI functions to VMs, so Page Requests are routed with RID:PASID, not PASID alone. The SMMU finds the struct device associated with the RID, and submits the fault with iommu_report_device_fault(). If the VF is assigned to a VM, then the page request gets injected into the VM, otherwise it uses the host IOPF handler
> > Could we have quota-free IOASID sets for the host? > > > Yes, perhaps just add a flag such that the set has its own namespace. > You mean have this quota-free IOASID set even co-exist with VMs? I still > don't get how PRQ works. > > That is not the use case for VT-d in that we have to have system-wide > allocation for host PASIDs. We have enqcmd which can take a PASID from > the per task MSR and deliver to multiple devices, so even though the > PASID table is per device the PASID name space must be global. > > > For the SMMU I'd like to allocate two sets, one SVA and one private > > for auxiliary domains, and I don't think giving either a quota makes > > much sense at the moment. > I agree we don;t need the quota if we don't support guest SVA at the > same time. > > So the sva set and aux_domain set PASIDs have their own namespaces?
They share the same PASID space, but they store different objects (mm_struct and context descriptor, respectively) so they need different ioasid_set tokens.
> > > There can be systems using only SVA and > > systems using only private PASIDs. I think it should be > > first-come-first-served until admins want a knob to define a policy > > themselves, based on cgroups for example. > > > > > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> > > > --- > > > drivers/iommu/intel-iommu.c | 8 +++++++- > > > drivers/iommu/ioasid.c | 9 +++++++++ > > > include/linux/ioasid.h | 9 +++++++++ > > > 3 files changed, 25 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/iommu/intel-iommu.c > > > b/drivers/iommu/intel-iommu.c index ec3fc121744a..af7a1ef7b31e > > > 100644 --- a/drivers/iommu/intel-iommu.c > > > +++ b/drivers/iommu/intel-iommu.c > > > @@ -3511,8 +3511,14 @@ static int __init init_dmars(void) > > > goto free_iommu; > > > > > > /* PASID is needed for scalable mode irrespective to SVM */ > > > - if (intel_iommu_sm) > > > + if (intel_iommu_sm) { > > > ioasid_install_capacity(intel_pasid_max_id); > > > + /* We should not run out of IOASIDs at boot */ > > > + if (ioasid_alloc_system_set(PID_MAX_DEFAULT)) { > > > + pr_err("Failed to enable host PASID > > > allocator\n"); > > > + intel_iommu_sm = 0; > > > + } > > > + } > > > > > > /* > > > * for each drhd > > > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c > > > index 6265d2dbbced..9135af171a7c 100644 > > > --- a/drivers/iommu/ioasid.c > > > +++ b/drivers/iommu/ioasid.c > > > @@ -39,6 +39,9 @@ struct ioasid_data { > > > static ioasid_t ioasid_capacity; > > > static ioasid_t ioasid_capacity_avail; > > > > > > +int system_ioasid_sid; > > > +static DECLARE_IOASID_SET(system_ioasid); > > > + > > > /* System capacity can only be set once */ > > > void ioasid_install_capacity(ioasid_t total) > > > { > > > @@ -51,6 +54,12 @@ void ioasid_install_capacity(ioasid_t total) > > > } > > > EXPORT_SYMBOL_GPL(ioasid_install_capacity); > > > > > > +int ioasid_alloc_system_set(int quota) > > > +{ > > > + return ioasid_alloc_set(&system_ioasid, quota, > > > &system_ioasid_sid); +} > > > +EXPORT_SYMBOL_GPL(ioasid_alloc_system_set); > > > > I think this helper could stay in the VT-d driver for the moment. If > > the SMMU driver ever implements auxiliary domains it will use a > > private IOASID set, separate from the shared IOASID set managed by > > iommu-sva. Both could qualify as "system set". > > > Sounds good. Perhaps remove the special "system set". SVA code, > VFIO, VT-d, or SMMU driver can all allocate their own sets. > So to meet both SMMU and VT-d requirements, we should do: > 1. add an IOASID_PRIVATE flag to ioasid_alloc_set(), indicating this is > a private set > 2. All APIs operate on the set_id accordingly, e.g. ioasid_find() will > only search within the private set. Private set is excluded from from > global search (VT-d needs this in PRQ). > > Since VT-d already needs private PASIDs for guest SVM where > GPASID!=HPASID, I feel we can just reuse the per ioasid_set Xarray for > both quota-free private set and guest set.
Ok I think this sounds fine
Thanks, Jean
> > > Thanks for the feedback! > > Jacob > > > Thanks, > > Jean > > > > > + > > > /* > > > * struct ioasid_allocator_data - Internal data structure to hold > > > information > > > * about an allocator. There are two types of allocators: > > > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h > > > index 8c82d2625671..097b1cc043a3 100644 > > > --- a/include/linux/ioasid.h > > > +++ b/include/linux/ioasid.h > > > @@ -29,6 +29,9 @@ struct ioasid_allocator_ops { > > > void *pdata; > > > }; > > > > > > +/* Shared IOASID set for reserved for host system use */ > > > +extern int system_ioasid_sid; > > > + > > > #define DECLARE_IOASID_SET(name) struct ioasid_set name = { 0 } > > > > > > #if IS_ENABLED(CONFIG_IOASID) > > > @@ -41,6 +44,7 @@ int ioasid_register_allocator(struct > > > ioasid_allocator_ops *allocator); void > > > ioasid_unregister_allocator(struct ioasid_allocator_ops > > > *allocator); int ioasid_attach_data(ioasid_t ioasid, void *data); > > > void ioasid_install_capacity(ioasid_t total); +int > > > ioasid_alloc_system_set(int quota); int ioasid_alloc_set(struct > > > ioasid_set *token, ioasid_t quota, int *sid); void > > > ioasid_free_set(int sid, bool destroy_set); int > > > ioasid_find_sid(ioasid_t ioasid); @@ -88,5 +92,10 @@ static inline > > > void ioasid_install_capacity(ioasid_t total) { > > > } > > > > > > +static inline int ioasid_alloc_system_set(int quota) > > > +{ > > > + return -ENOTSUPP; > > > +} > > > + > > > #endif /* CONFIG_IOASID */ > > > #endif /* __LINUX_IOASID_H */ > > > -- > > > 2.7.4 > > > > > [Jacob Pan]
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