iommu/vt-d: Retrieve IOMMU perfmon capability information

The performance monitoring infrastructure, perfmon, is to support
collection of information about key events occurring during operation of
the remapping hardware, to aid performance tuning and debug. Each
remapping hardware unit has capability registers that indicate support
for performance monitoring features and enumerate the capabilities.

Add alloc_iommu_pmu() to retrieve IOMMU perfmon capability information
for each iommu unit. The information is stored in the iommu->pmu data
structure. Capability registers are read-only, so it's safe to prefetch
and store them in the pmu structure. This could avoid unnecessary VMEXIT
when this code is running in the virtualization environment.

Add free_iommu_pmu() to free the saved capability information when
freeing the iommu unit.

Add a kernel config option for the IOMMU perfmon feature. Unless a user
explicitly uses the perf tool to monitor the IOMMU perfmon event, there
isn't any impact for the existing IOMMU. Enable it by default.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/r/20230128200428.1459118-3-kan.liang@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 172 insertions, 0 deletions

diff --git a/drivers/iommu/intel/perfmon.c b/drivers/iommu/intel/perfmon.c
new file mode 100644
index 000000000000..db5791a54455
--- /dev/null
+++ b/drivers/iommu/intel/perfmon.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Support Intel IOMMU PerfMon
+ * Copyright(c) 2023 Intel Corporation.
+ */
+#define pr_fmt(fmt)	"DMAR: " fmt
+#define dev_fmt(fmt)	pr_fmt(fmt)
+
+#include <linux/dmar.h>
+#include "iommu.h"
+#include "perfmon.h"
+
+static inline void __iomem *
+get_perf_reg_address(struct intel_iommu *iommu, u32 offset)
+{
+	u32 off = dmar_readl(iommu->reg + offset);
+
+	return iommu->reg + off;
+}
+
+int alloc_iommu_pmu(struct intel_iommu *iommu)
+{
+	struct iommu_pmu *iommu_pmu;
+	int i, j, ret;
+	u64 perfcap;
+	u32 cap;
+
+	if (!ecap_pms(iommu->ecap))
+		return 0;
+
+	/* The IOMMU PMU requires the ECMD support as well */
+	if (!cap_ecmds(iommu->cap))
+		return -ENODEV;
+
+	perfcap = dmar_readq(iommu->reg + DMAR_PERFCAP_REG);
+	/* The performance monitoring is not supported. */
+	if (!perfcap)
+		return -ENODEV;
+
+	/* Sanity check for the number of the counters and event groups */
+	if (!pcap_num_cntr(perfcap) || !pcap_num_event_group(perfcap))
+		return -ENODEV;
+
+	/* The interrupt on overflow is required */
+	if (!pcap_interrupt(perfcap))
+		return -ENODEV;
+
+	iommu_pmu = kzalloc(sizeof(*iommu_pmu), GFP_KERNEL);
+	if (!iommu_pmu)
+		return -ENOMEM;
+
+	iommu_pmu->num_cntr = pcap_num_cntr(perfcap);
+	iommu_pmu->cntr_width = pcap_cntr_width(perfcap);
+	iommu_pmu->filter = pcap_filters_mask(perfcap);
+	iommu_pmu->cntr_stride = pcap_cntr_stride(perfcap);
+	iommu_pmu->num_eg = pcap_num_event_group(perfcap);
+
+	iommu_pmu->evcap = kcalloc(iommu_pmu->num_eg, sizeof(u64), GFP_KERNEL);
+	if (!iommu_pmu->evcap) {
+		ret = -ENOMEM;
+		goto free_pmu;
+	}
+
+	/* Parse event group capabilities */
+	for (i = 0; i < iommu_pmu->num_eg; i++) {
+		u64 pcap;
+
+		pcap = dmar_readq(iommu->reg + DMAR_PERFEVNTCAP_REG +
+				  i * IOMMU_PMU_CAP_REGS_STEP);
+		iommu_pmu->evcap[i] = pecap_es(pcap);
+	}
+
+	iommu_pmu->cntr_evcap = kcalloc(iommu_pmu->num_cntr, sizeof(u32 *), GFP_KERNEL);
+	if (!iommu_pmu->cntr_evcap) {
+		ret = -ENOMEM;
+		goto free_pmu_evcap;
+	}
+	for (i = 0; i < iommu_pmu->num_cntr; i++) {
+		iommu_pmu->cntr_evcap[i] = kcalloc(iommu_pmu->num_eg, sizeof(u32), GFP_KERNEL);
+		if (!iommu_pmu->cntr_evcap[i]) {
+			ret = -ENOMEM;
+			goto free_pmu_cntr_evcap;
+		}
+		/*
+		 * Set to the global capabilities, will adjust according
+		 * to per-counter capabilities later.
+		 */
+		for (j = 0; j < iommu_pmu->num_eg; j++)
+			iommu_pmu->cntr_evcap[i][j] = (u32)iommu_pmu->evcap[j];
+	}
+
+	iommu_pmu->cfg_reg = get_perf_reg_address(iommu, DMAR_PERFCFGOFF_REG);
+	iommu_pmu->cntr_reg = get_perf_reg_address(iommu, DMAR_PERFCNTROFF_REG);
+	iommu_pmu->overflow = get_perf_reg_address(iommu, DMAR_PERFOVFOFF_REG);
+
+	/*
+	 * Check per-counter capabilities. All counters should have the
+	 * same capabilities on Interrupt on Overflow Support and Counter
+	 * Width.
+	 */
+	for (i = 0; i < iommu_pmu->num_cntr; i++) {
+		cap = dmar_readl(iommu_pmu->cfg_reg +
+				 i * IOMMU_PMU_CFG_OFFSET +
+				 IOMMU_PMU_CFG_CNTRCAP_OFFSET);
+		if (!iommu_cntrcap_pcc(cap))
+			continue;
+
+		/*
+		 * It's possible that some counters have a different
+		 * capability because of e.g., HW bug. Check the corner
+		 * case here and simply drop those counters.
+		 */
+		if ((iommu_cntrcap_cw(cap) != iommu_pmu->cntr_width) ||
+		    !iommu_cntrcap_ios(cap)) {
+			iommu_pmu->num_cntr = i;
+			pr_warn("PMU counter capability inconsistent, counter number reduced to %d\n",
+				iommu_pmu->num_cntr);
+		}
+
+		/* Clear the pre-defined events group */
+		for (j = 0; j < iommu_pmu->num_eg; j++)
+			iommu_pmu->cntr_evcap[i][j] = 0;
+
+		/* Override with per-counter event capabilities */
+		for (j = 0; j < iommu_cntrcap_egcnt(cap); j++) {
+			cap = dmar_readl(iommu_pmu->cfg_reg + i * IOMMU_PMU_CFG_OFFSET +
+					 IOMMU_PMU_CFG_CNTREVCAP_OFFSET +
+					 (j * IOMMU_PMU_OFF_REGS_STEP));
+			iommu_pmu->cntr_evcap[i][iommu_event_group(cap)] = iommu_event_select(cap);
+			/*
+			 * Some events may only be supported by a specific counter.
+			 * Track them in the evcap as well.
+			 */
+			iommu_pmu->evcap[iommu_event_group(cap)] |= iommu_event_select(cap);
+		}
+	}
+
+	iommu_pmu->iommu = iommu;
+	iommu->pmu = iommu_pmu;
+
+	return 0;
+
+free_pmu_cntr_evcap:
+	for (i = 0; i < iommu_pmu->num_cntr; i++)
+		kfree(iommu_pmu->cntr_evcap[i]);
+	kfree(iommu_pmu->cntr_evcap);
+free_pmu_evcap:
+	kfree(iommu_pmu->evcap);
+free_pmu:
+	kfree(iommu_pmu);
+
+	return ret;
+}
+
+void free_iommu_pmu(struct intel_iommu *iommu)
+{
+	struct iommu_pmu *iommu_pmu = iommu->pmu;
+
+	if (!iommu_pmu)
+		return;
+
+	if (iommu_pmu->evcap) {
+		int i;
+
+		for (i = 0; i < iommu_pmu->num_cntr; i++)
+			kfree(iommu_pmu->cntr_evcap[i]);
+		kfree(iommu_pmu->cntr_evcap);
+	}
+	kfree(iommu_pmu->evcap);
+	kfree(iommu_pmu);
+	iommu->pmu = NULL;
+}