iommu/amd: Access/Dirty bit support in IOPTEs

IOMMU advertises Access/Dirty bits if the extended feature register reports
it. Relevant AMD IOMMU SDM ref[0] "1.3.8 Enhanced Support for Access and
Dirty Bits"

To enable it set the DTE flag in bits 7 and 8 to enable access, or
access+dirty. With that, the IOMMU starts marking the D and A flags on
every Memory Request or ATS translation request. It is on the VMM side to
steer whether to enable dirty tracking or not, rather than wrongly doing in
IOMMU. Relevant AMD IOMMU SDM ref [0], "Table 7. Device Table Entry (DTE)
Field Definitions" particularly the entry "HAD".

To actually toggle on and off it's relatively simple as it's setting 2 bits
on DTE and flush the device DTE cache.

To get what's dirtied use existing AMD io-pgtable support, by walking the
pagetables over each IOVA, with fetch_pte().  The IOTLB flushing is left to
the caller (much like unmap), and iommu_dirty_bitmap_record() is the one
adding page-ranges to invalidate. This allows caller to batch the flush
over a big span of IOVA space, without the iommu wondering about when to
flush.

Worthwhile sections from AMD IOMMU SDM:

"2.2.3.1 Host Access Support"
"2.2.3.2 Host Dirty Support"

For details on how IOMMU hardware updates the dirty bit see, and expects
from its consequent clearing by CPU:

"2.2.7.4 Updating Accessed and Dirty Bits in the Guest Address Tables"
"2.2.7.5 Clearing Accessed and Dirty Bits"

Quoting the SDM:

"The setting of accessed and dirty status bits in the page tables is
visible to both the CPU and the peripheral when sharing guest page tables.
The IOMMU interlocked operations to update A and D bits must be 64-bit
operations and naturally aligned on a 64-bit boundary"

.. and for the IOMMU update sequence to Dirty bit, essentially is states:

1. Decodes the read and write intent from the memory access.
2. If P=0 in the page descriptor, fail the access.
3. Compare the A & D bits in the descriptor with the read and write
intent in the request.
4. If the A or D bits need to be updated in the descriptor:
* Start atomic operation.
* Read the descriptor as a 64-bit access.
* If the descriptor no longer appears to require an update, release the
atomic lock with
no further action and continue to step 5.
* Calculate the new A & D bits.
* Write the descriptor as a 64-bit access.
* End atomic operation.
5. Continue to the next stage of translation or to the memory access.

Access/Dirty bits readout also need to consider the non-default page-sizes
(aka replicated PTEs as mentined by manual), as AMD supports all powers of
two (except 512G) page sizes.

Select IOMMUFD_DRIVER only if IOMMUFD is enabled considering that IOMMU
dirty tracking requires IOMMUFD.

Link: https://lore.kernel.org/r/20231024135109.73787-12-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 7dc30c2b56b3..dec4e5c2b66b 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -97,7 +97,9 @@
 #define FEATURE_GATS_MASK	(3ULL)
 #define FEATURE_GAM_VAPIC	BIT_ULL(21)
 #define FEATURE_GIOSUP		BIT_ULL(48)
+#define FEATURE_HASUP		BIT_ULL(49)
 #define FEATURE_EPHSUP		BIT_ULL(50)
+#define FEATURE_HDSUP		BIT_ULL(52)
 #define FEATURE_SNP		BIT_ULL(63)
 
 #define FEATURE_PASID_SHIFT	32
@@ -212,6 +214,7 @@
 /* macros and definitions for device table entries */
 #define DEV_ENTRY_VALID         0x00
 #define DEV_ENTRY_TRANSLATION   0x01
+#define DEV_ENTRY_HAD           0x07
 #define DEV_ENTRY_PPR           0x34
 #define DEV_ENTRY_IR            0x3d
 #define DEV_ENTRY_IW            0x3e
@@ -371,9 +374,15 @@
 	(1ULL << (12 + (9 * (level))))
 
 /*
+ * The IOPTE dirty bit
+ */
+#define IOMMU_PTE_HD_BIT (6)
+
+/*
  * Bit value definition for I/O PTE fields
  */
 #define IOMMU_PTE_PR	BIT_ULL(0)
+#define IOMMU_PTE_HD	BIT_ULL(IOMMU_PTE_HD_BIT)
 #define IOMMU_PTE_U	BIT_ULL(59)
 #define IOMMU_PTE_FC	BIT_ULL(60)
 #define IOMMU_PTE_IR	BIT_ULL(61)
@@ -384,6 +393,7 @@
  */
 #define DTE_FLAG_V	BIT_ULL(0)
 #define DTE_FLAG_TV	BIT_ULL(1)
+#define DTE_FLAG_HAD	(3ULL << 7)
 #define DTE_FLAG_GIOV	BIT_ULL(54)
 #define DTE_FLAG_GV	BIT_ULL(55)
 #define DTE_GLX_SHIFT	(56)
@@ -413,6 +423,7 @@
 
 #define IOMMU_PAGE_MASK (((1ULL << 52) - 1) & ~0xfffULL)
 #define IOMMU_PTE_PRESENT(pte) ((pte) & IOMMU_PTE_PR)
+#define IOMMU_PTE_DIRTY(pte) ((pte) & IOMMU_PTE_HD)
 #define IOMMU_PTE_PAGE(pte) (iommu_phys_to_virt((pte) & IOMMU_PAGE_MASK))
 #define IOMMU_PTE_MODE(pte) (((pte) >> 9) & 0x07)
 
@@ -563,6 +574,7 @@ struct protection_domain {
 	int nid;		/* Node ID */
 	u64 *gcr3_tbl;		/* Guest CR3 table */
 	unsigned long flags;	/* flags to find out type of domain */
+	bool dirty_tracking;	/* dirty tracking is enabled in the domain */
 	unsigned dev_cnt;	/* devices assigned to this domain */
 	unsigned dev_iommu[MAX_IOMMUS]; /* per-IOMMU reference count */
 };