[PATCH v6][RESEND] x86/hyperv: Suspend/resume the hypercall page for hibernation

From: Dexuan Cui
Date: Mon Jan 06 2020 - 17:43:32 EST


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@xxxxxxxxxxxxx>
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
---

This is a RESEND of https://lkml.org/lkml/2019/11/20/68 .

Please review.

If it looks good, can you please pick it up through the tip.git tree?


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 caaf4dce99bf..24a62d33067c 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -21,11 +21,15 @@
#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);

@@ -246,6 +250,46 @@ 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.
@@ -330,6 +374,8 @@ void __init hyperv_init(void)

x86_init.pci.arch_init = hv_pci_init;

+ register_syscore_ops(&hv_syscore_ops);
+
return;

remove_cpuhp_state:
@@ -349,6 +395,8 @@ 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