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From:   Dexuan Cui <decui@microsoft.com>
To:     "arnd@arndb.de" <arnd@arndb.de>, "bp@alien8.de" <bp@alien8.de>,
        "daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>,
        Haiyang Zhang <haiyangz@microsoft.com>,
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        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "sashal@kernel.org" <sashal@kernel.org>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "x86@kernel.org" <x86@kernel.org>,
        Michael Kelley <mikelley@microsoft.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
CC:     "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        Dexuan Cui <decui@microsoft.com>
Subject: [PATCH v5 1/3] x86/hyper-v: Suspend/resume the hypercall page for
 hibernation
Thread-Topic: [PATCH v5 1/3] x86/hyper-v: Suspend/resume the hypercall page
 for hibernation
Thread-Index: AQHVZDvbqcf4mG84E0mgdKNCoP1lHA==
Date:   Thu, 5 Sep 2019 22:47:12 +0000
Message-ID: <1567723581-29088-2-git-send-email-decui@microsoft.com>
References: <1567723581-29088-1-git-send-email-decui@microsoft.com>
In-Reply-To: <1567723581-29088-1-git-send-email-decui@microsoft.com>
Reply-To: Dexuan Cui <decui@microsoft.com>
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This is needed for hibernation, e.g. when we resume the old kernel, we need
to disable the "current" kernel's hypercall page and then resume the old
kernel's.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
 arch/x86/hyperv/hv_init.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 866dfb3..037b0f3 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -20,6 +20,7 @@
 #include <linux/hyperv.h>
 #include <linux/slab.h>
 #include <linux/cpuhotplug.h>
+#include <linux/syscore_ops.h>
 #include <clocksource/hyperv_timer.h>
=20
 void *hv_hypercall_pg;
@@ -223,6 +224,34 @@ static int __init hv_pci_init(void)
 	return 1;
 }
=20
+static int hv_suspend(void)
+{
+	union hv_x64_msr_hypercall_contents hypercall_msr;
+
+	/* Reset the hypercall page */
+	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+	hypercall_msr.enable =3D 0;
+	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+	return 0;
+}
+
+static void hv_resume(void)
+{
+	union hv_x64_msr_hypercall_contents hypercall_msr;
+
+	/* Re-enable the hypercall page */
+	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+	hypercall_msr.enable =3D 1;
+	hypercall_msr.guest_physical_address =3D vmalloc_to_pfn(hv_hypercall_pg);
+	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+}
+
+static struct syscore_ops hv_syscore_ops =3D {
+	.suspend =3D hv_suspend,
+	.resume =3D hv_resume,
+};
+
 /*
  * This function is to be invoked early in the boot sequence after the
  * hypervisor has been detected.
@@ -301,6 +330,8 @@ void __init hyperv_init(void)
=20
 	x86_init.pci.arch_init =3D hv_pci_init;
=20
+	register_syscore_ops(&hv_syscore_ops);
+
 	return;
=20
 remove_cpuhp_state:
@@ -320,6 +351,8 @@ void hyperv_cleanup(void)
 {
 	union hv_x64_msr_hypercall_contents hypercall_msr;
=20
+	unregister_syscore_ops(&hv_syscore_ops);
+
 	/* Reset our OS id */
 	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
=20
--=20
1.8.3.1