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[focal:linux-azure,18/21] x86/hyperv: Suspend/resume the hypercall page for hibernation

Message ID 20200602020817.236422-19-marcelo.cerri@canonical.com
State New
Headers show
Series LP:#1880032 - [linux-azure] Enable Hibernation on The 18.04 and 20.04 5.4 Kernels | expand

Commit Message

Marcelo Henrique Cerri June 2, 2020, 2:08 a.m. UTC 
From: Dexuan Cui <decui@microsoft.com>

BugLink: http://bugs.launchpad.net/bugs/1880032

For hibernation the hypercall page must be disabled before the hibernation
image is created so that subsequent hypercall operations fail safely. On
resume the hypercall page has to be restored and reenabled to ensure proper
operation of the resumed kernel.

Implement the necessary suspend/resume callbacks.

[ tglx: Decrypted changelog ]

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1578350559-130275-1-git-send-email-decui@microsoft.com

(cherry picked from commit 05bd330a7fd8875c423fc07d8ddcad73c10e556e)
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
---
 arch/x86/hyperv/hv_init.c | 50 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
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Patch

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index b4c49cabb436..ce15f4228fde 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -22,6 +22,7 @@ 
 #include <linux/slab.h>
 #include <linux/kernel.h>
 #include <linux/cpuhotplug.h>
+#include <linux/syscore_ops.h>
 #include <clocksource/hyperv_timer.h>
 
 #ifndef PKG_ABI
@@ -35,6 +36,9 @@ 
 void *hv_hypercall_pg;
 EXPORT_SYMBOL_GPL(hv_hypercall_pg);
 
+/* Storage to save the hypercall page temporarily for hibernation */
+static void *hv_hypercall_pg_saved;
+
 u32 *hv_vp_index;
 EXPORT_SYMBOL_GPL(hv_vp_index);
 
@@ -247,6 +251,48 @@  static int __init hv_pci_init(void)
 	return 1;
 }
 
+static int hv_suspend(void)
+{
+	union hv_x64_msr_hypercall_contents hypercall_msr;
+
+	/*
+	 * Reset the hypercall page as it is going to be invalidated
+	 * accross hibernation. Setting hv_hypercall_pg to NULL ensures
+	 * that any subsequent hypercall operation fails safely instead of
+	 * crashing due to an access of an invalid page. The hypercall page
+	 * pointer is restored on resume.
+	 */
+	hv_hypercall_pg_saved = hv_hypercall_pg;
+	hv_hypercall_pg = NULL;
+
+	/* Disable the hypercall page in the hypervisor */
+	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.
@@ -331,6 +377,8 @@  void __init hyperv_init(void)
 
 	x86_init.pci.arch_init = hv_pci_init;
 
+	register_syscore_ops(&hv_syscore_ops);
+
 	return;
 
 remove_cpuhp_state:
@@ -350,6 +398,8 @@  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);