[PATCH v2 1/3] iommu: amd: Use 4K page for completion wait write-back semaphore

From: Suravee Suthikulpanit
Date: Wed Sep 23 2020 - 08:11:22 EST


IOMMU SNP support requires the completion wait write-back semaphore to be
implemented using a 4K-aligned page, where the page address is to be
programmed into the newly introduced MMIO base/range registers.

This new scheme uses a per-iommu atomic variable to store the current
semaphore value, which is incremented for every completion wait command.

Since this new scheme is also compatible with non-SNP mode,
generalize the driver to use 4K page for completion-wait semaphore in
both modes.

Cc: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
drivers/iommu/amd/amd_iommu_types.h | 3 ++-
drivers/iommu/amd/init.c | 18 ++++++++++++++++++
drivers/iommu/amd/iommu.c | 23 +++++++++++------------
3 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 30a5d412255a..4c80483e78ec 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -595,7 +595,8 @@ struct amd_iommu {
#endif

u32 flags;
- volatile u64 __aligned(8) cmd_sem;
+ volatile u64 *cmd_sem;
+ u64 cmd_sem_val;

#ifdef CONFIG_AMD_IOMMU_DEBUGFS
/* DebugFS Info */
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 445a08d23fed..febc072f2717 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -813,6 +813,19 @@ static int iommu_init_ga(struct amd_iommu *iommu)
return ret;
}

+static int __init alloc_cwwb_sem(struct amd_iommu *iommu)
+{
+ iommu->cmd_sem = (void *)get_zeroed_page(GFP_KERNEL);
+
+ return iommu->cmd_sem ? 0 : -ENOMEM;
+}
+
+static void __init free_cwwb_sem(struct amd_iommu *iommu)
+{
+ if (iommu->cmd_sem)
+ free_page((unsigned long)iommu->cmd_sem);
+}
+
static void iommu_enable_xt(struct amd_iommu *iommu)
{
#ifdef CONFIG_IRQ_REMAP
@@ -1395,6 +1408,7 @@ static int __init init_iommu_from_acpi(struct amd_iommu *iommu,

static void __init free_iommu_one(struct amd_iommu *iommu)
{
+ free_cwwb_sem(iommu);
free_command_buffer(iommu);
free_event_buffer(iommu);
free_ppr_log(iommu);
@@ -1481,6 +1495,7 @@ static int __init init_iommu_one(struct amd_iommu *iommu, struct ivhd_header *h)
int ret;

raw_spin_lock_init(&iommu->lock);
+ iommu->cmd_sem_val = 0;

/* Add IOMMU to internal data structures */
list_add_tail(&iommu->list, &amd_iommu_list);
@@ -1558,6 +1573,9 @@ static int __init init_iommu_one(struct amd_iommu *iommu, struct ivhd_header *h)
if (!iommu->mmio_base)
return -ENOMEM;

+ if (alloc_cwwb_sem(iommu))
+ return -ENOMEM;
+
if (alloc_command_buffer(iommu))
return -ENOMEM;

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 10e4200d3552..9e9898683537 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -792,11 +792,11 @@ irqreturn_t amd_iommu_int_handler(int irq, void *data)
*
****************************************************************************/

-static int wait_on_sem(volatile u64 *sem)
+static int wait_on_sem(struct amd_iommu *iommu, u64 data)
{
int i = 0;

- while (*sem == 0 && i < LOOP_TIMEOUT) {
+ while (*iommu->cmd_sem != data && i < LOOP_TIMEOUT) {
udelay(1);
i += 1;
}
@@ -827,16 +827,16 @@ static void copy_cmd_to_buffer(struct amd_iommu *iommu,
writel(tail, iommu->mmio_base + MMIO_CMD_TAIL_OFFSET);
}

-static void build_completion_wait(struct iommu_cmd *cmd, u64 address)
+static void build_completion_wait(struct iommu_cmd *cmd,
+ struct amd_iommu *iommu,
+ u64 data)
{
- u64 paddr = iommu_virt_to_phys((void *)address);
-
- WARN_ON(address & 0x7ULL);
+ u64 paddr = iommu_virt_to_phys((void *)iommu->cmd_sem);

memset(cmd, 0, sizeof(*cmd));
cmd->data[0] = lower_32_bits(paddr) | CMD_COMPL_WAIT_STORE_MASK;
cmd->data[1] = upper_32_bits(paddr);
- cmd->data[2] = 1;
+ cmd->data[2] = data;
CMD_SET_TYPE(cmd, CMD_COMPL_WAIT);
}

@@ -1045,22 +1045,21 @@ static int iommu_completion_wait(struct amd_iommu *iommu)
struct iommu_cmd cmd;
unsigned long flags;
int ret;
+ u64 data;

if (!iommu->need_sync)
return 0;

-
- build_completion_wait(&cmd, (u64)&iommu->cmd_sem);
-
raw_spin_lock_irqsave(&iommu->lock, flags);

- iommu->cmd_sem = 0;
+ data = ++iommu->cmd_sem_val;
+ build_completion_wait(&cmd, iommu, data);

ret = __iommu_queue_command_sync(iommu, &cmd, false);
if (ret)
goto out_unlock;

- ret = wait_on_sem(&iommu->cmd_sem);
+ ret = wait_on_sem(iommu, data);

out_unlock:
raw_spin_unlock_irqrestore(&iommu->lock, flags);
--
2.17.1