From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: Wed, 14 Apr 2021 14:35:43 +0200
Subject: x86/kvm: Disable all PV features on crash
Patch-mainline: v5.13-rc2
Git-commit: 3d6b84132d2a57b5a74100f6923a8feb679ac2ce
References: bsc#1185308

Crash shutdown handler only disables kvmclock and steal time, other PV
features remain active so we risk corrupting memory or getting some
side-effects in kdump kernel. Move crash handler to kvm.c and unify
with CPU offline.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-5-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Liang Yan <lyan@suse.com>
---
 arch/x86/include/asm/kvm_para.h |    5 ----
 arch/x86/kernel/kvm.c           |   44 +++++++++++++++++++++++++++++-----------
 arch/x86/kernel/kvmclock.c      |   21 -------------------
 3 files changed, 32 insertions(+), 38 deletions(-)

--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -92,7 +92,6 @@ void __init kvm_guest_init(void);
 void kvm_async_pf_task_wait(u32 token, int interrupt_kernel);
 void kvm_async_pf_task_wake(u32 token);
 u32 kvm_read_and_reset_pf_reason(void);
-extern void kvm_disable_steal_time(void);
 
 #ifdef CONFIG_PARAVIRT_SPINLOCKS
 void __init kvm_spinlock_init(void);
@@ -122,10 +121,6 @@ static inline u32 kvm_read_and_reset_pf_
 	return 0;
 }
 
-static inline void kvm_disable_steal_time(void)
-{
-	return;
-}
 #endif
 
 #endif /* _ASM_X86_KVM_PARA_H */
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -47,6 +47,7 @@
 #include <asm/apicdef.h>
 #include <asm/hypervisor.h>
 #include <asm/kvm_guest.h>
+#include <asm/reboot.h>
 
 static int kvmapf = 1;
 
@@ -377,6 +378,14 @@ static void kvm_pv_disable_apf(void)
 	       smp_processor_id());
 }
 
+static void kvm_disable_steal_time(void)
+{
+	if (!has_steal_clock)
+		return;
+
+	wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
+}
+
 static void kvm_pv_guest_cpu_reboot(void *unused)
 {
 	/*
@@ -419,14 +428,6 @@ static u64 kvm_steal_clock(int cpu)
 	return steal;
 }
 
-void kvm_disable_steal_time(void)
-{
-	if (!has_steal_clock)
-		return;
-
-	wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
-}
-
 static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
 {
 	early_set_memory_decrypted((unsigned long) ptr, size);
@@ -454,13 +455,14 @@ static void __init sev_map_percpu_data(v
 	}
 }
 
-static void kvm_guest_cpu_offline(void)
+static void kvm_guest_cpu_offline(bool shutdown)
 {
 	kvm_disable_steal_time();
 	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 		wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 	kvm_pv_disable_apf();
-	apf_task_wake_all();
+	if (!shutdown)
+		apf_task_wake_all();
 	kvmclock_disable();
 }
 
@@ -493,7 +495,7 @@ static int kvm_cpu_down_prepare(unsigned
 	unsigned long flags;
 
 	local_irq_save(flags);
-	kvm_guest_cpu_offline();
+	kvm_guest_cpu_offline(false);
 	local_irq_restore(flags);
 	return 0;
 }
@@ -501,7 +503,7 @@ static int kvm_cpu_down_prepare(unsigned
 
 static int kvm_suspend(void)
 {
-	kvm_guest_cpu_offline();
+	kvm_guest_cpu_offline(false);
 
 	return 0;
 }
@@ -516,6 +518,20 @@ static struct syscore_ops kvm_syscore_op
 	.resume		= kvm_resume,
 };
 
+/*
+ * After a PV feature is registered, the host will keep writing to the
+ * registered memory location. If the guest happens to shutdown, this memory
+ * won't be valid. In cases like kexec, in which you install a new kernel, this
+ * means a random memory location will be kept being written.
+ */
+#ifdef CONFIG_KEXEC_CORE
+static void kvm_crash_shutdown(struct pt_regs *regs)
+{
+	kvm_guest_cpu_offline(true);
+	native_machine_crash_shutdown(regs);
+}
+#endif
+
 static void __init kvm_apf_trap_init(void)
 {
 	set_intr_gate(14, async_page_fault);
@@ -556,6 +572,10 @@ void __init kvm_guest_init(void)
 	kvm_guest_cpu_init();
 #endif
 
+#ifdef CONFIG_KEXEC_CORE
+	machine_ops.crash_shutdown = kvm_crash_shutdown;
+#endif
+
 	register_syscore_ops(&kvm_syscore_ops);
 
 	/*
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -29,7 +29,6 @@
 
 #include <asm/mem_encrypt.h>
 #include <asm/x86_init.h>
-#include <asm/reboot.h>
 #include <asm/kvmclock.h>
 
 static int kvmclock __ro_after_init = 1;
@@ -221,23 +220,6 @@ static void kvm_setup_secondary_clock(vo
 }
 #endif
 
-/*
- * After the clock is registered, the host will keep writing to the
- * registered memory location. If the guest happens to shutdown, this memory
- * won't be valid. In cases like kexec, in which you install a new kernel, this
- * means a random memory location will be kept being written. So before any
- * kind of shutdown from our side, we unregister the clock by writing anything
- * that does not have the 'enable' bit set in the msr
- */
-#ifdef CONFIG_KEXEC_CORE
-static void kvm_crash_shutdown(struct pt_regs *regs)
-{
-	native_write_msr(msr_kvm_system_time, 0, 0);
-	kvm_disable_steal_time();
-	native_machine_crash_shutdown(regs);
-}
-#endif
-
 void kvmclock_disable(void)
 {
 	native_write_msr(msr_kvm_system_time, 0, 0);
@@ -340,9 +322,6 @@ void __init kvmclock_init(void)
 #endif
 	x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
 	x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
-#ifdef CONFIG_KEXEC_CORE
-	machine_ops.crash_shutdown  = kvm_crash_shutdown;
-#endif
 	kvm_get_preset_lpj();
 	clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
 	pv_info.name = "KVM";