[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2 3/6] x86/iommu: introduce a rangeset to perform hwdom IOMMU setup
On Tue, Dec 05, 2023 at 03:50:44PM +0100, Jan Beulich wrote: > On 04.12.2023 10:43, Roger Pau Monne wrote: > > This change just introduces the boilerplate code in order to use a rangeset > > when setting up the hardware domain IOMMU mappings. The rangeset is never > > populated in this patch, so it's a non-functional change as far as the > > mappings > > the domain gets established. > > > > Note there's a change for HVM domains (ie: PVH dom0) that will get switched > > to > > create the p2m mappings using map_mmio_regions() instead of > > p2m_add_identity_entry(), so that ranges can be mapped with a single > > function > > call if possible. Note that the interface of map_mmio_regions() doesn't > > allow > > creating read-only mappings, but so far there are no such mappings created > > for > > PVH dom0 in arch_iommu_hwdom_init(). > > I don't understand this paragraph: The rangeset remains empty, so nothing is > changing right here. DYM there is going to be such a change as a result of > this patch, but in a later part of this series? Yes, when the rangeset is populated and mappings are created based on its contents, map_mmio_regions() will be used instead of p2m_add_identity_entry(). I guess the '... that will get switched to create the p2m ...' is not clear enough. > > --- a/xen/drivers/passthrough/x86/iommu.c > > +++ b/xen/drivers/passthrough/x86/iommu.c > > @@ -370,10 +370,77 @@ static unsigned int __hwdom_init > > hwdom_iommu_map(const struct domain *d, > > return perms; > > } > > > > +struct map_data { > > + struct domain *d; > > + unsigned int flush_flags; > > + bool ro; > > +}; > > + > > +static int __hwdom_init cf_check identity_map(unsigned long s, unsigned > > long e, > > + void *data) > > +{ > > + struct map_data *info = data; > > + struct domain *d = info->d; > > + long rc; > > + > > + if ( iommu_verbose ) > > + printk(XENLOG_INFO " [%010lx, %010lx] R%c\n", > > + s, e, info->ro ? 'O' : 'W'); > > + > > + if ( paging_mode_translate(d) ) > > + { > > + if ( info->ro ) > > + { > > + ASSERT_UNREACHABLE(); > > + return 0; > > + } > > + while ( (rc = map_mmio_regions(d, _gfn(s), e - s + 1, _mfn(s))) > > > 0 ) > > + { > > + s += rc; > > + process_pending_softirqs(); > > + } > > + } > > + else > > + { > > + const unsigned int perms = IOMMUF_readable | IOMMUF_preempt | > > + (info->ro ? 0 : IOMMUF_writable); > > + > > + if ( info->ro && !iomem_access_permitted(d, s, e) ) > > How is r/o-ness related to iomem_access_permitted()? The present callers > are such that there is a connection, but that's invisible here. I guess > either the field wants to change name (maybe mmio_ro or ro_mmio or even > just mmio), or there wants to be a comment. Will add: "read-only ranges are only created based on the contents of mmio_ro_ranges, and hence need the additional iomem_access_permitted() check." > > + { > > + /* > > + * Should be more fine grained in order to not map the > > forbidden > > + * frame instead of rejecting the region as a whole, but it's > > only > > + * for read-only MMIO regions, which are very limited. > > + */ > > How certain are you/we that no two adjacent ones may appear, with > different permissions granted to Dom0? Yeah, I was already not very convinced by this, and I think the only solution here is to iterate over the read-only ranges with page granularity. In any case read-only ranges are both few and small in size, hence this is unlikely to be noticeable performance wise. > > + printk(XENLOG_DEBUG > > + "IOMMU read-only mapping of region [%lx, %lx] > > forbidden\n", > > + s, e); > > + return 0; > > + } > > + while ( (rc = iommu_map(d, _dfn(s), _mfn(s), e - s + 1, > > + perms, &info->flush_flags)) > 0 ) > > + { > > + s += rc; > > + process_pending_softirqs(); > > + } > > + } > > + ASSERT(rc <= 0); > > + if ( rc ) > > + printk(XENLOG_WARNING > > + "IOMMU identity mapping of [%lx, %lx] failed: %ld\n", > > + s, e, rc); > > + > > + /* Ignore errors and attempt to map the remaining regions. */ > > + return 0; > > +} > > + > > void __hwdom_init arch_iommu_hwdom_init(struct domain *d) > > { > > unsigned long i, top, max_pfn, start, count; > > unsigned int flush_flags = 0, start_perms = 0; > > + struct rangeset *map; > > + struct map_data map_data = { .d = d }; > > + int rc; > > > > BUG_ON(!is_hardware_domain(d)); > > > > @@ -397,6 +464,10 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain > > *d) > > if ( iommu_hwdom_passthrough ) > > return; > > > > + map = rangeset_new(NULL, NULL, 0); > > + if ( !map ) > > + panic("IOMMU init: unable to allocate rangeset\n"); > > + > > max_pfn = (GB(4) >> PAGE_SHIFT) - 1; > > top = max(max_pdx, pfn_to_pdx(max_pfn) + 1); > > > > @@ -451,6 +522,24 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain > > *d) > > goto commit; > > } > > > > + if ( iommu_verbose ) > > + printk(XENLOG_INFO "d%u: identity mappings for IOMMU:\n", > > + d->domain_id); > > %pd: ? Indeed, I probably copied this from a different chunk and didn't adjust to use %pd. > > + rc = rangeset_report_ranges(map, 0, ~0UL, identity_map, &map_data); > > + if ( rc ) > > + panic("IOMMU unable to create mappings: %d\n", rc); > > + if ( is_pv_domain(d) ) > > + { > > + map_data.ro = true; > > + rc = rangeset_report_ranges(mmio_ro_ranges, 0, ~0UL, identity_map, > > + &map_data); > > + if ( rc ) > > + panic("IOMMU unable to create read-only mappings: %d\n", rc); > > + } > > + > > + rangeset_destroy(map); > > This could move up, couldn't it? Yes, could be moved just after the rangeset_report_ranges(map...) call. > > /* Use if to avoid compiler warning */ > > if ( iommu_iotlb_flush_all(d, flush_flags) ) > > Don't you need to fold map.flush_flags into flush_flags ahead of this call? > Or can the variable perhaps go away altogether, being replaced by the struct > field? Yes, the variable ends up being replaced in a later patch, hence I didn't touch it here. Thanks, Roger.
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