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Message-ID: <20240916171805.324292-3-suravee.suthikulpanit@amd.com>
Date: Mon, 16 Sep 2024 17:18:01 +0000
From: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To: <linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>
CC: <joro@...tes.org>, <robin.murphy@....com>, <vasant.hegde@....com>,
<jgg@...dia.com>, <kevin.tian@...el.com>, <jon.grimm@....com>,
<santosh.shukla@....com>, <pandoh@...gle.com>, <kumaranand@...gle.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v4 2/6] iommu/amd: Introduce helper function to update 256-bit DTE
The current implementation does not follow 128-bit write requirement
to update DTE as specified in the AMD I/O Virtualization Techonology
(IOMMU) Specification.
Therefore, modify the struct dev_table_entry to contain union of u128 data
array, and introduce a helper functions update_dte256() to update DTE using
two 128-bit cmpxchg operations to update 256-bit DTE with the modified
structure, and take into account the DTE[V, GV] bits when programming
the DTE to ensure proper order of DTE programming and flushing.
In addition, introduce a per-DTE spin_lock struct dev_data.dte_lock to
provide synchronization when updating the DTE to prevent cmpxchg128
failure.
Suggested-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
drivers/iommu/amd/amd_iommu.h | 2 +
drivers/iommu/amd/amd_iommu_types.h | 8 ++-
drivers/iommu/amd/iommu.c | 96 +++++++++++++++++++++++++++++
3 files changed, 105 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
index 52e18b5f99fd..14a153c7bc12 100644
--- a/drivers/iommu/amd/amd_iommu.h
+++ b/drivers/iommu/amd/amd_iommu.h
@@ -28,6 +28,8 @@ void iommu_feature_enable(struct amd_iommu *iommu, u8 bit);
void *__init iommu_alloc_4k_pages(struct amd_iommu *iommu,
gfp_t gfp, size_t size);
+int iommu_flush_sync_dte(struct amd_iommu *iommu, u16 devid);
+
#ifdef CONFIG_AMD_IOMMU_DEBUGFS
void amd_iommu_debugfs_setup(struct amd_iommu *iommu);
#else
diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index c9f9a598eb82..fea7544f8c55 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -427,6 +427,8 @@
#define GCR3_VALID 0x01ULL
+#define DTE_INTR_MASK (~GENMASK_ULL(55, 52))
+
#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)
@@ -833,6 +835,7 @@ struct devid_map {
struct iommu_dev_data {
/*Protect against attach/detach races */
spinlock_t lock;
+ spinlock_t dte_lock; /* DTE lock for 256-bit access */
struct list_head list; /* For domain->dev_list */
struct llist_node dev_data_list; /* For global dev_data_list */
@@ -883,7 +886,10 @@ extern struct amd_iommu *amd_iommus[MAX_IOMMUS];
* Structure defining one entry in the device table
*/
struct dev_table_entry {
- u64 data[4];
+ union {
+ u64 data[4];
+ u128 data128[2];
+ };
};
/*
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 87c5385ce3f2..48a721d10f06 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -85,6 +85,91 @@ static void set_dte_entry(struct amd_iommu *iommu,
*
****************************************************************************/
+static void write_upper(struct dev_table_entry *ptr, struct dev_table_entry *new)
+{
+ struct dev_table_entry old = {};
+
+ do {
+ old.data128[1] = ptr->data128[1];
+ new->data[2] &= ~DTE_INTR_MASK;
+ new->data[2] |= (old.data[2] & DTE_INTR_MASK);
+ } while (!try_cmpxchg128(&ptr->data128[1], &old.data128[1], new->data128[1]));
+}
+
+static void write_lower(struct dev_table_entry *ptr, struct dev_table_entry *new)
+{
+ struct dev_table_entry old = {};
+
+ do {
+ old.data128[0] = ptr->data128[0];
+ } while (!try_cmpxchg128(&ptr->data128[0], &old.data128[0], new->data128[0]));
+}
+
+/*
+ * Note:
+ * IOMMU reads the entire Device Table entry in a single 256-bit transaction
+ * but the driver is programming DTE using 2 128-bit cmpxchg. So, the driver
+ * need to ensure the following:
+ * - DTE[V|GV] bit is being written last when setting.
+ * - DTE[V|GV] bit is being written first when clearing.
+ *
+ * This function is used only by code, which updates DMA translation part of the DTE.
+ * So, only consider control bits related to DMA when updating the entry.
+ */
+static void update_dte256(struct amd_iommu *iommu, struct iommu_dev_data *dev_data,
+ struct dev_table_entry *new)
+{
+ struct dev_table_entry *dev_table = get_dev_table(iommu);
+ struct dev_table_entry *ptr = &dev_table[dev_data->devid];
+
+ spin_lock(&dev_data->dte_lock);
+
+ if (!(ptr->data[0] & DTE_FLAG_V)) {
+ /* Existing DTE is not valid. */
+ write_upper(ptr, new);
+ write_lower(ptr, new);
+ iommu_flush_sync_dte(iommu, dev_data->devid);
+ } else if (!(new->data[0] & DTE_FLAG_V)) {
+ /* Existing DTE is valid. New DTE is not valid. */
+ write_lower(ptr, new);
+ write_upper(ptr, new);
+ iommu_flush_sync_dte(iommu, dev_data->devid);
+ } else {
+ /* Existing & new DTEs are valid. */
+ if (!FIELD_GET(DTE_FLAG_GV, ptr->data[0])) {
+ /* Existing DTE has no guest page table. */
+ write_upper(ptr, new);
+ write_lower(ptr, new);
+ iommu_flush_sync_dte(iommu, dev_data->devid);
+ } else if (!FIELD_GET(DTE_FLAG_GV, new->data[0])) {
+ /*
+ * Existing DTE has guest page table,
+ * new DTE has no guest page table,
+ */
+ write_lower(ptr, new);
+ write_upper(ptr, new);
+ iommu_flush_sync_dte(iommu, dev_data->devid);
+ } else {
+ /*
+ * Existing DTE has guest page table,
+ * new DTE has guest page table.
+ */
+ struct dev_table_entry clear = {};
+
+ /* First disable DTE */
+ write_lower(ptr, &clear);
+ iommu_flush_sync_dte(iommu, dev_data->devid);
+
+ /* Then update DTE */
+ write_upper(ptr, new);
+ write_lower(ptr, new);
+ iommu_flush_sync_dte(iommu, dev_data->devid);
+ }
+ }
+
+ spin_unlock(&dev_data->dte_lock);
+}
+
static inline bool pdom_is_v2_pgtbl_mode(struct protection_domain *pdom)
{
return (pdom && (pdom->pd_mode == PD_MODE_V2));
@@ -205,6 +290,7 @@ static struct iommu_dev_data *alloc_dev_data(struct amd_iommu *iommu, u16 devid)
return NULL;
spin_lock_init(&dev_data->lock);
+ spin_lock_init(&dev_data->dte_lock);
dev_data->devid = devid;
ratelimit_default_init(&dev_data->rs);
@@ -1256,6 +1342,16 @@ static int iommu_flush_dte(struct amd_iommu *iommu, u16 devid)
return iommu_queue_command(iommu, &cmd);
}
+int iommu_flush_sync_dte(struct amd_iommu *iommu, u16 devid)
+{
+ int ret;
+
+ ret = iommu_flush_dte(iommu, devid);
+ if (!ret)
+ iommu_completion_wait(iommu);
+ return ret;
+}
+
static void amd_iommu_flush_dte_all(struct amd_iommu *iommu)
{
u32 devid;
--
2.34.1
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