From adfd373820906d376c8b643f1a279ac809605b6b Mon Sep 17 00:00:00 2001 From: Eric Auger Date: Mon, 3 Jun 2019 08:53:35 +0200 Subject: [PATCH] iommu: Introduce IOMMU_RESV_DIRECT_RELAXABLE reserved memory regions 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 Signed-off-by: Joerg Roedel --- Documentation/ABI/testing/sysfs-kernel-iommu_groups | 9 +++++++++ drivers/iommu/iommu.c | 12 +++++++----- include/linux/iommu.h | 6 ++++++ 3 files changed, 22 insertions(+), 5 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups index 35c64e00b35c..017f5bc3920c 100644 --- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups +++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups @@ -24,3 +24,12 @@ Description: /sys/kernel/iommu_groups/reserved_regions list IOVA region is described on a single line: the 1st field is the base IOVA, the second is the end IOVA and the third field describes the type of the region. + +What: /sys/kernel/iommu_groups/reserved_regions +Date: June 2019 +KernelVersion: v5.3 +Contact: Eric Auger +Description: In case an RMRR is used only by graphics or USB devices + it is now exposed as "direct-relaxable" instead of "direct". + In device assignment use case, for instance, those RMRR + are considered to be relaxable and safe. diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index ba0661744a3d..46a06ff46e47 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-relaxable", + [IOMMU_RESV_RESERVED] = "reserved", + [IOMMU_RESV_MSI] = "msi", + [IOMMU_RESV_SW_MSI] = "msi", }; #define IOMMU_GROUP_ATTR(_name, _mode, _show, _store) \ @@ -575,7 +576,8 @@ 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 && + 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 91af22a344e2..ab7a1c85af75 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) */ -- 2.30.2