[RFCv2 02/16] x86/kvm: Introduce KVM memory protection feature

From: Kirill A. Shutemov
Date: Tue Oct 20 2020 - 02:21:32 EST


Provide basic helpers, KVM_FEATURE, CPUID flag 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/cpufeatures.h | 1 +
arch/x86/include/asm/kvm_para.h | 5 +++++
arch/x86/include/uapi/asm/kvm_para.h | 3 ++-
arch/x86/kernel/kvm.c | 18 ++++++++++++++++++
include/uapi/linux/kvm_para.h | 3 ++-
5 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 2901d5df4366..a72157137764 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -236,6 +236,7 @@
#define X86_FEATURE_EPT_AD ( 8*32+17) /* Intel Extended Page Table access-dirty bit */
#define X86_FEATURE_VMCALL ( 8*32+18) /* "" Hypervisor supports the VMCALL instruction */
#define X86_FEATURE_VMW_VMMCALL ( 8*32+19) /* "" VMware prefers VMMCALL hypercall instruction */
+#define X86_FEATURE_KVM_MEM_PROTECTED ( 8*32+20) /* KVM memory protection extenstion */

/* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */
#define X86_FEATURE_FSGSBASE ( 9*32+ 0) /* RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 338119852512..74aea18f3130 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -11,11 +11,16 @@ 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 812e9b4c1114..defbfc630a9f 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -28,10 +28,11 @@
#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_ASYNC_PF_INT 14
+#define KVM_FEATURE_MEM_PROTECTED 15

#define KVM_HINTS_REALTIME 0

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 9663ba31347c..2c1f8952b92a 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -37,6 +37,13 @@
#include <asm/tlb.h>
#include <asm/cpuidle_haltpoll.h>

+static bool mem_protected;
+
+bool kvm_mem_protected(void)
+{
+ return mem_protected;
+}
+
DEFINE_STATIC_KEY_FALSE(kvm_async_pf_enabled);

static int kvmapf = 1;
@@ -742,6 +749,17 @@ 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;
+ }
+
+ pr_info("KVM memory protection enabled\n");
+ mem_protected = true;
+ setup_force_cpu_cap(X86_FEATURE_KVM_MEM_PROTECTED);
+ }
}

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