iommu: Introduce IOMMU_RESV_DIRECT_RELAXABLE reserved memory regions (adfd3738) · Commits · 戴 / test

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 ("iommu/vt-d: Exclude devices using RMRRs from IOMMU API domains") and commit ("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.auger@redhat.com> Signed-off-by:

Joerg Roedel <jroedel@suse.de>

Documentation/ABI/testing/sysfs-kernel-iommu_groups

+9 −0

Original line number	Diff line number	Diff line
		@@ -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 <eric.auger@redhat.com>
		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.

drivers/iommu/iommu.c

+7 −5

Original line number	Diff line number	Diff line
		@@ -74,6 +74,7 @@ struct iommu_group_attribute {

		static const char * const iommu_group_resv_type_string[] = {
		[IOMMU_RESV_DIRECT] = "direct",
		[IOMMU_RESV_DIRECT_RELAXABLE] = "direct-relaxable",
		[IOMMU_RESV_RESERVED] = "reserved",
		[IOMMU_RESV_MSI] = "msi",
		[IOMMU_RESV_SW_MSI] = "msi",
		@@ -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) {

include/linux/iommu.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -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) */

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