[PATCH AUTOSEL 5.11 09/52] iommu/vt-d: Clear PRQ overflow only when PRQ is empty

[PATCH AUTOSEL 5.11 09/52] iommu/vt-d: Clear PRQ overflow only when PRQ is empty

[Sasha Levin]

From: Lu Baolu <baolu.lu@linux.intel.com>

[ Upstream commit 28a77185f1cd0650b664f54614143aaaa3a7a615 ]

It is incorrect to always clear PRO when it's set w/o first checking
whether the overflow condition has been cleared. Current code assumes
that if an overflow condition occurs it must have been cleared by earlier
loop. However since the code runs in a threaded context, the overflow
condition could occur even after setting the head to the tail under some
extreme condition. To be sane, we should read both head/tail again when
seeing a pending PRO and only clear PRO after all pending PRs have been
handled.

Suggested-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/linux-iommu/MWHPR11MB18862D2EA5BD432BF22D99A48CA09@MWHPR11MB1886.namprd11.prod.outlook.com/
Link: https://lore.kernel.org/r/20210126080730.2232859-2-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/intel/svm.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 18a9f05df407..b3bcd6dec93e 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -1079,8 +1079,17 @@ prq_advance:
 	 * Clear the page request overflow bit and wake up all threads that
 	 * are waiting for the completion of this handling.
 	 */
-	if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO)
-		writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG);
+	if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO) {
+		pr_info_ratelimited("IOMMU: %s: PRQ overflow detected\n",
+				    iommu->name);
+		head = dmar_readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
+		tail = dmar_readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK;
+		if (head == tail) {
+			writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG);
+			pr_info_ratelimited("IOMMU: %s: PRQ overflow cleared",
+					    iommu->name);
+		}
+	}
 
 	if (!completion_done(&iommu->prq_complete))
 		complete(&iommu->prq_complete);
-- 
2.30.1

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[PATCH AUTOSEL 5.11 25/52] iommu/amd: Fix performance counter initialization

[Sasha Levin]

From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>

[ Upstream commit 6778ff5b21bd8e78c8bd547fd66437cf2657fd9b ]

Certain AMD platforms enable power gating feature for IOMMU PMC,
which prevents the IOMMU driver from updating the counter while
trying to validate the PMC functionality in the init_iommu_perf_ctr().
This results in disabling PMC support and the following error message:

    "AMD-Vi: Unable to read/write to IOMMU perf counter"

To workaround this issue, disable power gating temporarily by programming
the counter source to non-zero value while validating the counter,
and restore the prior state afterward.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Tj (Elloe Linux) <ml.linux@elloe.vision>
Link: https://lore.kernel.org/r/20210208122712.5048-1-suravee.suthikulpanit@amd.com
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201753
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/amd/init.c | 45 ++++++++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 11 deletions(-)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 83d8ab2aed9f..01da76dc1caa 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -12,6 +12,7 @@
 #include <linux/acpi.h>
 #include <linux/list.h>
 #include <linux/bitmap.h>
+#include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/syscore_ops.h>
 #include <linux/interrupt.h>
@@ -254,6 +255,8 @@ static enum iommu_init_state init_state = IOMMU_START_STATE;
 static int amd_iommu_enable_interrupts(void);
 static int __init iommu_go_to_state(enum iommu_init_state state);
 static void init_device_table_dma(void);
+static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr,
+				u8 fxn, u64 *value, bool is_write);
 
 static bool amd_iommu_pre_enabled = true;
 
@@ -1712,13 +1715,11 @@ static int __init init_iommu_all(struct acpi_table_header *table)
 	return 0;
 }
 
-static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr,
-				u8 fxn, u64 *value, bool is_write);
-
-static void init_iommu_perf_ctr(struct amd_iommu *iommu)
+static void __init init_iommu_perf_ctr(struct amd_iommu *iommu)
 {
+	int retry;
 	struct pci_dev *pdev = iommu->dev;
-	u64 val = 0xabcd, val2 = 0, save_reg = 0;
+	u64 val = 0xabcd, val2 = 0, save_reg, save_src;
 
 	if (!iommu_feature(iommu, FEATURE_PC))
 		return;
@@ -1726,17 +1727,39 @@ static void init_iommu_perf_ctr(struct amd_iommu *iommu)
 	amd_iommu_pc_present = true;
 
 	/* save the value to restore, if writable */
-	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false))
+	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false) ||
+	    iommu_pc_get_set_reg(iommu, 0, 0, 8, &save_src, false))
 		goto pc_false;
 
-	/* Check if the performance counters can be written to */
-	if ((iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true)) ||
-	    (iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false)) ||
-	    (val != val2))
+	/*
+	 * Disable power gating by programing the performance counter
+	 * source to 20 (i.e. counts the reads and writes from/to IOMMU
+	 * Reserved Register [MMIO Offset 1FF8h] that are ignored.),
+	 * which never get incremented during this init phase.
+	 * (Note: The event is also deprecated.)
+	 */
+	val = 20;
+	if (iommu_pc_get_set_reg(iommu, 0, 0, 8, &val, true))
 		goto pc_false;
 
+	/* Check if the performance counters can be written to */
+	val = 0xabcd;
+	for (retry = 5; retry; retry--) {
+		if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true) ||
+		    iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false) ||
+		    val2)
+			break;
+
+		/* Wait about 20 msec for power gating to disable and retry. */
+		msleep(20);
+	}
+
 	/* restore */
-	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true))
+	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true) ||
+	    iommu_pc_get_set_reg(iommu, 0, 0, 8, &save_src, true))
+		goto pc_false;
+
+	if (val != val2)
 		goto pc_false;
 
 	pci_info(pdev, "IOMMU performance counters supported\n");
-- 
2.30.1

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