linux-kernel - [RFC 4/9] RISC-V: KVM: Improve privilege mode filtering for perf

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Date:   Mon, 18 Jul 2022 10:02:00 -0700
From:   Atish Patra <atishp@...osinc.com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atishp@...osinc.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Guo Ren <guoren@...nel.org>, kvm-riscv@...ts.infradead.org,
        kvm@...r.kernel.org, linux-riscv@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Will Deacon <will@...nel.org>
Subject: [RFC  4/9] RISC-V: KVM: Improve privilege mode filtering for perf

Currently, the host driver doesn't have any method to identify if the
requested perf event is from kvm or bare metal. As KVM runs in HS
mode, there are no separate hypervisor privilege mode to distinguish
between the attributes for guest/host.

Improve the privilege mode filtering by using the event specific
config1 field.

Signed-off-by: Atish Patra <atishp@...osinc.com>
---
 drivers/perf/riscv_pmu_sbi.c   | 27 ++++++++++++++++++++++-----
 include/linux/perf/riscv_pmu.h |  2 ++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 5d0eef3ef136..34f9fcc221a8 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -275,6 +275,27 @@ int riscv_pmu_sbi_hpmc_width(void)
 }
 EXPORT_SYMBOL(riscv_pmu_sbi_hpmc_width);
 
+static unsigned long pmu_sbi_get_filter_flags(struct perf_event *event)
+{
+	unsigned long cflags = 0;
+	bool guest_events = false;
+
+	if (event->attr.config1 & RISCV_KVM_PMU_CONFIG1_GUEST_EVENTS)
+		guest_events = true;
+	if (event->attr.exclude_kernel)
+		cflags |= guest_events ? SBI_PMU_CFG_FLAG_SET_VSINH : SBI_PMU_CFG_FLAG_SET_SINH;
+	if (event->attr.exclude_user)
+		cflags |= guest_events ? SBI_PMU_CFG_FLAG_SET_VUINH : SBI_PMU_CFG_FLAG_SET_UINH;
+	if (guest_events && event->attr.exclude_hv)
+		cflags |= SBI_PMU_CFG_FLAG_SET_SINH;
+	if (event->attr.exclude_host)
+		cflags |= SBI_PMU_CFG_FLAG_SET_UINH | SBI_PMU_CFG_FLAG_SET_SINH;
+	if (event->attr.exclude_guest)
+		cflags |= SBI_PMU_CFG_FLAG_SET_VSINH | SBI_PMU_CFG_FLAG_SET_VUINH;
+
+	return cflags;
+}
+
 static int pmu_sbi_ctr_get_idx(struct perf_event *event)
 {
 	struct hw_perf_event *hwc = &event->hw;
@@ -286,11 +307,7 @@ static int pmu_sbi_ctr_get_idx(struct perf_event *event)
 	uint64_t cmask = GENMASK_ULL(rvpmu->num_counters - 1, 0);
 	unsigned long cflags = 0;
 
-	if (event->attr.exclude_kernel)
-		cflags |= SBI_PMU_CFG_FLAG_SET_SINH;
-	if (event->attr.exclude_user)
-		cflags |= SBI_PMU_CFG_FLAG_SET_UINH;
-
+	cflags = pmu_sbi_get_filter_flags(event);
 	/* retrieve the available counter index */
 #if defined(CONFIG_32BIT)
 	ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_CFG_MATCH, cbase, cmask,
diff --git a/include/linux/perf/riscv_pmu.h b/include/linux/perf/riscv_pmu.h
index 6fee211c27b5..825b95253bc5 100644
--- a/include/linux/perf/riscv_pmu.h
+++ b/include/linux/perf/riscv_pmu.h
@@ -26,6 +26,8 @@
 
 #define RISCV_PMU_STOP_FLAG_RESET 1
 
+#define RISCV_KVM_PMU_CONFIG1_GUEST_EVENTS 0x1
+
 struct cpu_hw_events {
 	/* currently enabled events */
 	int			n_events;
-- 
2.25.1