Hi On 5/16/19 10:47 AM, Eric Auger wrote: > Introduce a new type for reserved region. This corresponds > to directly mapped regions which are known to be relaxable > in some specific conditions, such as device assignment use > case. Well known examples are those used by USB controllers > providing PS/2 keyboard emulation for pre-boot BIOS and > early BOOT or RMRRs associated to IGD working in legacy mode. > > Since commit c875d2c1b808 ("iommu/vt-d: Exclude devices using RMRRs > from IOMMU API domains") and commit 18436afdc11a ("iommu/vt-d: Allow > RMRR on graphics devices too"), those regions are currently > considered "safe" with respect to device assignment use case > which requires a non direct mapping at IOMMU physical level > (RAM GPA -> HPA mapping). > > Those RMRRs currently exist and sometimes the device is > attempting to access it but this has not been considered > an issue until now. > > However at the moment, iommu_get_group_resv_regions() is > not able to make any difference between directly mapped > regions: those which must be absolutely enforced and those > like above ones which are known as relaxable. > > This is a blocker for reporting severe conflicts between > non relaxable RMRRs (like MSI doorbells) and guest GPA space. > > With this new reserved region type we will be able to use > iommu_get_group_resv_regions() to enumerate the IOVA space > that is usable through the IOMMU API without introducing > regressions with respect to existing device assignment > use cases (USB and IGD). > > Signed-off-by: Eric Auger <eric.au...@redhat.com> > > --- > > Note: At the moment the sysfs ABI is not changed. However I wonder > whether it wouldn't be preferable to report the direct region as > "direct_relaxed" there. At the moment, in case the same direct > region is used by 2 devices, one USB/GFX and another not belonging > to the previous categories, the direct region will be output twice > with "direct" type. > > This would unblock Shameer's series: > [PATCH v6 0/7] vfio/type1: Add support for valid iova list management > https://patchwork.kernel.org/patch/10425309/ > > which failed to get pulled for 4.18 merge window due to IGD > device assignment regression. > --- > drivers/iommu/iommu.c | 12 +++++++----- > include/linux/iommu.h | 6 ++++++ > 2 files changed, 13 insertions(+), 5 deletions(-) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index ae4ea5c0e6f9..84dcb6af6511 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -73,10 +73,11 @@ struct iommu_group_attribute { > }; > > static const char * const iommu_group_resv_type_string[] = { > - [IOMMU_RESV_DIRECT] = "direct", > - [IOMMU_RESV_RESERVED] = "reserved", > - [IOMMU_RESV_MSI] = "msi", > - [IOMMU_RESV_SW_MSI] = "msi", > + [IOMMU_RESV_DIRECT] = "direct", > + [IOMMU_RESV_DIRECT_RELAXABLE] = "direct", > + [IOMMU_RESV_RESERVED] = "reserved", > + [IOMMU_RESV_MSI] = "msi", > + [IOMMU_RESV_SW_MSI] = "msi", > }; > > #define IOMMU_GROUP_ATTR(_name, _mode, _show, _store) \ > @@ -573,7 +574,8 @@ static int iommu_group_create_direct_mappings(struct > iommu_group *group, > start = ALIGN(entry->start, pg_size); > end = ALIGN(entry->start + entry->length, pg_size); > > - if (entry->type != IOMMU_RESV_DIRECT) > + if (entry->type != IOMMU_RESV_DIRECT || It must be a "&&" and not "||"
Respinning ... Eric > + entry->type != IOMMU_RESV_DIRECT_RELAXABLE) > continue; > > for (addr = start; addr < end; addr += pg_size) { > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > index ba91666998fb..14a521f85f14 100644 > --- a/include/linux/iommu.h > +++ b/include/linux/iommu.h > @@ -135,6 +135,12 @@ enum iommu_attr { > enum iommu_resv_type { > /* Memory regions which must be mapped 1:1 at all times */ > IOMMU_RESV_DIRECT, > + /* > + * Memory regions which are advertised to be 1:1 but are > + * commonly considered relaxable in some conditions, > + * for instance in device assignment use case (USB, Graphics) > + */ > + IOMMU_RESV_DIRECT_RELAXABLE, > /* Arbitrary "never map this or give it to a device" address ranges */ > IOMMU_RESV_RESERVED, > /* Hardware MSI region (untranslated) */ >