Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Received-SPF: Pass (protection.outlook.com: domain of amd.com designates
 165.204.84.17 as permitted sender) receiver=protection.outlook.com;
 client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C
From:   Sandipan Das <sandipan.das@amd.com>
To:     <linux-kernel@vger.kernel.org>, <linux-perf-users@vger.kernel.org>,
        <x86@kernel.org>
CC:     <peterz@infradead.org>, <mingo@redhat.com>, <acme@kernel.org>,
        <mark.rutland@arm.com>, <alexander.shishkin@linux.intel.com>,
        <jolsa@kernel.org>, <namhyung@kernel.org>, <irogers@google.com>,
        <adrian.hunter@intel.com>, <tglx@linutronix.de>, <bp@alien8.de>,
        <dave.hansen@linux.intel.com>, <hpa@zytor.com>,
        <eranian@google.com>, <ananth.narayan@amd.com>,
        <ravi.bangoria@amd.com>, <santosh.shukla@amd.com>,
        <sandipan.das@amd.com>
Subject: [PATCH 2/6] perf/x86/amd/uncore: Use rdmsr if rdpmc is unavailable
Date:   Wed, 19 Jul 2023 12:25:37 +0530
Message-ID: <d48c60aea3a72c136811c0079f9802a988ee9271.1689748843.git.sandipan.das@amd.com>
In-Reply-To: <cover.1689748843.git.sandipan.das@amd.com>
References: <cover.1689748843.git.sandipan.das@amd.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Jul 2023 06:56:54.6155
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 37ab0781-7c32-4bb3-7124-08db88255652
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com]
X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT088.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB6804
X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO,
        RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE,
        T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=no autolearn_force=no
        version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Not all uncore PMUs may support the use of the RDPMC instruction for
reading counters. In such cases, read the count from the corresponding
PERF_CTR register using the RDMSR instruction.

Signed-off-by: Sandipan Das <sandipan.das@amd.com>
---
 arch/x86/events/amd/uncore.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
index b0afbe6d9eb4..f17df6574ba5 100644
--- a/arch/x86/events/amd/uncore.c
+++ b/arch/x86/events/amd/uncore.c
@@ -76,7 +76,16 @@ static void amd_uncore_read(struct perf_event *event)
 	 */
 
 	prev = local64_read(&hwc->prev_count);
-	rdpmcl(hwc->event_base_rdpmc, new);
+
+	/*
+	 * Some uncore PMUs do not have RDPMC assignments. In such cases,
+	 * read counts directly from the corresponding PERF_CTR.
+	 */
+	if (hwc->event_base_rdpmc < 0)
+		rdmsrl(hwc->event_base, new);
+	else
+		rdpmcl(hwc->event_base_rdpmc, new);
+
 	local64_set(&hwc->prev_count, new);
 	delta = (new << COUNTER_SHIFT) - (prev << COUNTER_SHIFT);
 	delta >>= COUNTER_SHIFT;
@@ -144,6 +153,9 @@ static int amd_uncore_add(struct perf_event *event, int flags)
 	hwc->event_base_rdpmc = uncore->rdpmc_base + hwc->idx;
 	hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
 
+	if (uncore->rdpmc_base < 0)
+		hwc->event_base_rdpmc = -1;
+
 	if (flags & PERF_EF_START)
 		event->pmu->start(event, PERF_EF_RELOAD);
 
-- 
2.34.1