Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Dexuan Cui <decui@microsoft.com>
To:     arnd@arndb.de, bp@alien8.de, daniel.lezcano@linaro.org,
        haiyangz@microsoft.com, hpa@zytor.com, kys@microsoft.com,
        linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
        mingo@redhat.com, sashal@kernel.org, sthemmin@microsoft.com,
        tglx@linutronix.de, x86@kernel.org, mikelley@microsoft.com,
        Alexander.Levin@microsoft.com, vkuznets@redhat.com
Cc:     linux-arch@vger.kernel.org, Dexuan Cui <decui@microsoft.com>
Subject: [PATCH v6][RESEND] clocksource/drivers: Suspend/resume Hyper-V clocksource for hibernation
Date:   Mon,  6 Jan 2020 14:43:37 -0800
Message-Id: <1578350617-130430-1-git-send-email-decui@microsoft.com>
Reply-To: decui@microsoft.com
Content-Type: text/plain
MIME-Version: 1.0
Received-SPF: None (protection.outlook.com: microsoft.com does not designate
 permitted sender hosts)
X-MS-Exchange-CrossTenant-Network-Message-Id: a58a8c36-02f4-4097-dba1-08d792f9e323
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jan 2020 22:43:45.3423
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 72f988bf-86f1-41af-91ab-2d7cd011db47
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: FN6QqSYulpuhvmLbusnTHjRXveULcr8Lz8FKxNg2o788U8CikT+HM3BS/vAzHC4GxUkt5nTjYleL/chw1pVu2g==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR21MB0471
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

This is needed for hibernation, e.g. when we resume the old kernel, we need
to disable the "current" kernel's TSC page and then resume the old kernel's.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---

This is a RESEND of https://lore.kernel.org/patchwork/patch/1156212/ .

Daniel Lezcano said "Applied, thanks!" on 12/4/2019 (see the above link),
but I still can not find it in the mainline tree, or the tip tree. 

So, let me resend it just in case.

 drivers/clocksource/hyperv_timer.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 287d8d58c21a..1aec08e82b7a 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -330,12 +330,37 @@ static u64 read_hv_sched_clock_tsc(void)
 	return read_hv_clock_tsc(NULL) - hv_sched_clock_offset;
 }
 
+static void suspend_hv_clock_tsc(struct clocksource *arg)
+{
+	u64 tsc_msr;
+
+	/* Disable the TSC page */
+	hv_get_reference_tsc(tsc_msr);
+	tsc_msr &= ~BIT_ULL(0);
+	hv_set_reference_tsc(tsc_msr);
+}
+
+
+static void resume_hv_clock_tsc(struct clocksource *arg)
+{
+	phys_addr_t phys_addr = virt_to_phys(&tsc_pg);
+	u64 tsc_msr;
+
+	/* Re-enable the TSC page */
+	hv_get_reference_tsc(tsc_msr);
+	tsc_msr &= GENMASK_ULL(11, 0);
+	tsc_msr |= BIT_ULL(0) | (u64)phys_addr;
+	hv_set_reference_tsc(tsc_msr);
+}
+
 static struct clocksource hyperv_cs_tsc = {
 	.name	= "hyperv_clocksource_tsc_page",
 	.rating	= 400,
 	.read	= read_hv_clock_tsc,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.suspend= suspend_hv_clock_tsc,
+	.resume	= resume_hv_clock_tsc,
 };
 
 static u64 notrace read_hv_clock_msr(struct clocksource *arg)
-- 
2.19.1