[RFC 02/16] x86/kvm: Introduce KVM memory protection feature

["Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>]

Provide basic helpers, KVM_FEATURE and a hypercall.

Host side doesn't provide the feature yet, so it is a dead code for now.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/kvm_para.h      |  5 +++++
 arch/x86/include/uapi/asm/kvm_para.h |  3 ++-
 arch/x86/kernel/kvm.c                | 16 ++++++++++++++++
 include/uapi/linux/kvm_para.h        |  3 ++-
 4 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 9b4df6eaa11a..3ce84fc07144 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -10,11 +10,16 @@ extern void kvmclock_init(void);
 
 #ifdef CONFIG_KVM_GUEST
 bool kvm_check_and_clear_guest_paused(void);
+bool kvm_mem_protected(void);
 #else
 static inline bool kvm_check_and_clear_guest_paused(void)
 {
 	return false;
 }
+static inline bool kvm_mem_protected(void)
+{
+	return false;
+}
 #endif /* CONFIG_KVM_GUEST */
 
 #define KVM_HYPERCALL \
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 2a8e0b6b9805..c3b499acc98f 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -28,9 +28,10 @@
 #define KVM_FEATURE_PV_UNHALT		7
 #define KVM_FEATURE_PV_TLB_FLUSH	9
 #define KVM_FEATURE_ASYNC_PF_VMEXIT	10
-#define KVM_FEATURE_PV_SEND_IPI	11
+#define KVM_FEATURE_PV_SEND_IPI		11
 #define KVM_FEATURE_POLL_CONTROL	12
 #define KVM_FEATURE_PV_SCHED_YIELD	13
+#define KVM_FEATURE_MEM_PROTECTED	14
 
 #define KVM_HINTS_REALTIME      0
 
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 6efe0410fb72..bda761ca0d26 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -35,6 +35,13 @@
 #include <asm/tlb.h>
 #include <asm/cpuidle_haltpoll.h>
 
+static bool mem_protected;
+
+bool kvm_mem_protected(void)
+{
+	return mem_protected;
+}
+
 static int kvmapf = 1;
 
 static int __init parse_no_kvmapf(char *arg)
@@ -727,6 +734,15 @@ static void __init kvm_init_platform(void)
 {
 	kvmclock_init();
 	x86_platform.apic_post_init = kvm_apic_init;
+
+	if (kvm_para_has_feature(KVM_FEATURE_MEM_PROTECTED)) {
+		if (kvm_hypercall0(KVM_HC_ENABLE_MEM_PROTECTED)) {
+			pr_err("Failed to enable KVM memory protection\n");
+			return;
+		}
+
+		mem_protected = true;
+	}
 }
 
 const __initconst struct hypervisor_x86 x86_hyper_kvm = {
diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
index 8b86609849b9..1a216f32e572 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/linux/kvm_para.h
@@ -27,8 +27,9 @@
 #define KVM_HC_MIPS_EXIT_VM		7
 #define KVM_HC_MIPS_CONSOLE_OUTPUT	8
 #define KVM_HC_CLOCK_PAIRING		9
-#define KVM_HC_SEND_IPI		10
+#define KVM_HC_SEND_IPI			10
 #define KVM_HC_SCHED_YIELD		11
+#define KVM_HC_ENABLE_MEM_PROTECTED	12
 
 /*
  * hypercalls use architecture specific
-- 
2.26.2