From fb3af1f4fefb78f9180446aae2834e11a6f7d134 Mon Sep 17 00:00:00 2001 From: Dheeraj Kumar Srivastava Date: Wed, 2 Jul 2025 15:08:00 +0530 Subject: [PATCH] iommu/amd: Add debugfs support to dump IOMMU command buffer IOMMU driver sends command to IOMMU hardware via command buffer. In cases where IOMMU hardware fails to process commands in command buffer, dumping it is a valuable input to debug the issue. IOMMU hardware processes command buffer entry at offset equals to the head pointer. Dumping just the entry at the head pointer may not always be useful. The current head may not be pointing to the entry of the command buffer which is causing the issue. IOMMU Hardware may have processed the entry and updated the head pointer. So dumping the entire command buffer gives a broad understanding of what hardware was/is doing. The command buffer dump will have all entries from start to end of the command buffer. Along with that, it will have a head and tail command buffer pointer register dump to facilitate where the IOMMU driver and hardware are in the command buffer for injecting and processing the entries respectively. Command buffer is a per IOMMU data structure. So dumping on per IOMMU basis. eg. -> To get command buffer dump for iommu (say, iommu00) #cat /sys/kernel/debug/iommu/amd/iommu00/cmdbuf Signed-off-by: Dheeraj Kumar Srivastava Reviewed-by: Vasant Hegde Link: https://lore.kernel.org/r/20250702093804.849-5-dheerajkumar.srivastava@amd.com Signed-off-by: Will Deacon --- drivers/iommu/amd/amd_iommu_types.h | 7 +++++++ drivers/iommu/amd/debugfs.c | 26 ++++++++++++++++++++++++++ drivers/iommu/amd/iommu.c | 7 ------- 3 files changed, 33 insertions(+), 7 deletions(-) diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h index ac61f73a110bc..6875426082726 100644 --- a/drivers/iommu/amd/amd_iommu_types.h +++ b/drivers/iommu/amd/amd_iommu_types.h @@ -897,6 +897,13 @@ struct dev_table_entry { }; }; +/* + * Structure defining one entry in the command buffer + */ +struct iommu_cmd { + u32 data[4]; +}; + /* * Structure to sture persistent DTE flags from IVHD */ diff --git a/drivers/iommu/amd/debugfs.c b/drivers/iommu/amd/debugfs.c index f843e184a62b2..e78f6b217a7b3 100644 --- a/drivers/iommu/amd/debugfs.c +++ b/drivers/iommu/amd/debugfs.c @@ -107,6 +107,30 @@ static int iommu_capability_show(struct seq_file *m, void *unused) } DEFINE_SHOW_STORE_ATTRIBUTE(iommu_capability); +static int iommu_cmdbuf_show(struct seq_file *m, void *unused) +{ + struct amd_iommu *iommu = m->private; + struct iommu_cmd *cmd; + unsigned long flag; + u32 head, tail; + int i; + + raw_spin_lock_irqsave(&iommu->lock, flag); + head = readl(iommu->mmio_base + MMIO_CMD_HEAD_OFFSET); + tail = readl(iommu->mmio_base + MMIO_CMD_TAIL_OFFSET); + seq_printf(m, "CMD Buffer Head Offset:%d Tail Offset:%d\n", + (head >> 4) & 0x7fff, (tail >> 4) & 0x7fff); + for (i = 0; i < CMD_BUFFER_ENTRIES; i++) { + cmd = (struct iommu_cmd *)(iommu->cmd_buf + i * sizeof(*cmd)); + seq_printf(m, "%3d: %08x %08x %08x %08x\n", i, cmd->data[0], + cmd->data[1], cmd->data[2], cmd->data[3]); + } + raw_spin_unlock_irqrestore(&iommu->lock, flag); + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(iommu_cmdbuf); + void amd_iommu_debugfs_setup(void) { struct amd_iommu *iommu; @@ -125,5 +149,7 @@ void amd_iommu_debugfs_setup(void) &iommu_mmio_fops); debugfs_create_file("capability", 0644, iommu->debugfs, iommu, &iommu_capability_fops); + debugfs_create_file("cmdbuf", 0444, iommu->debugfs, iommu, + &iommu_cmdbuf_fops); } } diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c index d2d1deabf7e2a..1066cbea6c5a7 100644 --- a/drivers/iommu/amd/iommu.c +++ b/drivers/iommu/amd/iommu.c @@ -62,13 +62,6 @@ static const struct iommu_dirty_ops amd_dirty_ops; int amd_iommu_max_glx_val = -1; -/* - * general struct to manage commands send to an IOMMU - */ -struct iommu_cmd { - u32 data[4]; -}; - /* * AMD IOMMU allows up to 2^16 different protection domains. This is a bitmap * to know which ones are already in use. -- 2.47.2