[RFC 3/6] x86/hyper-v: allocate and use hv_vp_assist_pages

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

These pages are going to be used for Enlightened VMCS support in KVM.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 arch/x86/hyperv/hv_init.c       | 35 ++++++++++++++++++++++++++++++++++-
 arch/x86/include/asm/mshyperv.h |  1 +
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 189a398290db..a5eb0a89e299 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -85,6 +85,9 @@ EXPORT_SYMBOL_GPL(hyperv_cs);
 u32 *hv_vp_index;
 EXPORT_SYMBOL_GPL(hv_vp_index);
 
+struct hv_vp_assist_page **hv_vp_assist_page;
+EXPORT_SYMBOL_GPL(hv_vp_assist_page);
+
 u32 hv_max_vp_index;
 
 static int hv_cpu_init(unsigned int cpu)
@@ -98,6 +101,31 @@ static int hv_cpu_init(unsigned int cpu)
 	if (msr_vp_index > hv_max_vp_index)
 		hv_max_vp_index = msr_vp_index;
 
+	if (!hv_vp_assist_page[smp_processor_id()])
+		hv_vp_assist_page[smp_processor_id()] =
+			__vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
+
+	if (hv_vp_assist_page[smp_processor_id()]) {
+		u64 val;
+
+		val = vmalloc_to_pfn(hv_vp_assist_page[smp_processor_id()]);
+		val = (val << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) |
+			HV_X64_MSR_VP_ASSIST_PAGE_ENABLE;
+
+		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
+	}
+
+	return 0;
+}
+
+static int hv_cpu_die(unsigned int cpu)
+{
+	if (hv_vp_assist_page[cpu]) {
+		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
+		vfree(hv_vp_assist_page[cpu]);
+		hv_vp_assist_page[cpu] = NULL;
+	}
+
 	return 0;
 }
 
@@ -122,8 +150,13 @@ void hyperv_init(void)
 	if (!hv_vp_index)
 		return;
 
+	hv_vp_assist_page = kcalloc(num_possible_cpus(),
+				    sizeof(*hv_vp_assist_page), GFP_KERNEL);
+	if (!hv_vp_assist_page)
+		return;
+
 	if (cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv_init:online",
-			      hv_cpu_init, NULL) < 0)
+			      hv_cpu_init, hv_cpu_die) < 0)
 		goto free_vp_index;
 
 	/*
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 5400add2885b..245e08a2e48d 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -291,6 +291,7 @@ static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
  */
 extern u32 *hv_vp_index;
 extern u32 hv_max_vp_index;
+extern struct hv_vp_assist_page **hv_vp_assist_page;
 
 /**
  * hv_cpu_number_to_vp_number() - Map CPU to VP.
-- 
2.14.3