linux-kernel - [PATCH v6] x86/hyperv: Suspend/resume the hypercall page for hibernation

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Message-Id: <1574233742-47794-1-git-send-email-decui@microsoft.com>
Date:   Tue, 19 Nov 2019 23:09:02 -0800
From:   Dexuan Cui <decui@...rosoft.com>
To:     arnd@...db.de, bp@...en8.de, daniel.lezcano@...aro.org,
        haiyangz@...rosoft.com, hpa@...or.com, kys@...rosoft.com,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, sashal@...nel.org, sthemmin@...rosoft.com,
        tglx@...utronix.de, x86@...nel.org, mikelley@...rosoft.com,
        Alexander.Levin@...rosoft.com, vkuznets@...hat.com
Cc:     linux-arch@...r.kernel.org, Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v6] x86/hyperv: Suspend/resume the hypercall page for hibernation

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@...rosoft.com>
Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
---

This patch is part of the v5 patchset:
  https://lkml.org/lkml/2019/9/5/1158
  https://lkml.org/lkml/2019/9/5/1159 

  The change is: I set 'hv_hypercall_pg' to NULL in hv_suspend(), and
restore it in hv_resume(). This is suggested by Vitaly Kuznetsov.

  There is no other change, compared to v1 (v2~v5 were posted with the other
patches).

  Please pick up this patch onto the tip.git tree's branch x86/hyperv.

 arch/x86/hyperv/hv_init.c | 48 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 426dc8b78193..c170653da589 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -20,11 +20,15 @@
 #include <linux/hyperv.h>
 #include <linux/slab.h>
 #include <linux/cpuhotplug.h>
+#include <linux/syscore_ops.h>
 #include <clocksource/hyperv_timer.h>
 
 void *hv_hypercall_pg;
 EXPORT_SYMBOL_GPL(hv_hypercall_pg);
 
+/* Save the hypercall page temporarily for hibernation */
+static void *hv_hypercall_pg_saved;
+
 u32 *hv_vp_index;
 EXPORT_SYMBOL_GPL(hv_vp_index);
 
@@ -245,6 +249,46 @@ static int __init hv_pci_init(void)
 	return 1;
 }
 
+static int hv_suspend(void)
+{
+	union hv_x64_msr_hypercall_contents hypercall_msr;
+
+	/*
+	 * Reset hypercall page reference before reset the page,
+	 * let hypercall operations fail safely rather than
+	 * panic the kernel for using invalid hypercall page
+	 */
+	hv_hypercall_pg_saved = hv_hypercall_pg;
+	hv_hypercall_pg = NULL;
+
+	/* Reset the hypercall page */
+	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+	hypercall_msr.enable = 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 = 1;
+	hypercall_msr.guest_physical_address =
+		vmalloc_to_pfn(hv_hypercall_pg_saved);
+	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+	hv_hypercall_pg = hv_hypercall_pg_saved;
+	hv_hypercall_pg_saved = NULL;
+}
+
+static struct syscore_ops hv_syscore_ops = {
+	.suspend = hv_suspend,
+	.resume = hv_resume,
+};
+
 /*
  * This function is to be invoked early in the boot sequence after the
  * hypervisor has been detected.
@@ -329,6 +373,8 @@ void __init hyperv_init(void)
 
 	x86_init.pci.arch_init = hv_pci_init;
 
+	register_syscore_ops(&hv_syscore_ops);
+
 	return;
 
 remove_cpuhp_state:
@@ -348,6 +394,8 @@ void hyperv_cleanup(void)
 {
 	union hv_x64_msr_hypercall_contents hypercall_msr;
 
+	unregister_syscore_ops(&hv_syscore_ops);
+
 	/* Reset our OS id */
 	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
 
-- 
2.19.1