x86/kvm: Disable all PV features on crash

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>

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 9c56e0d..6929987 100644 (file)
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -92,7 +92,6 @@ unsigned int kvm_arch_para_hints(void);
 void kvm_async_pf_task_wait_schedule(u32 token);
 void kvm_async_pf_task_wake(u32 token);
 u32 kvm_read_and_reset_apf_flags(void);
-void kvm_disable_steal_time(void);
 bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token);
 
 DECLARE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
@@ -137,11 +136,6 @@ static inline u32 kvm_read_and_reset_apf_flags(void)
        return 0;
 }
 
-static inline void kvm_disable_steal_time(void)
-{
-       return;
-}
-
 static __always_inline bool kvm_handle_async_pf(struct pt_regs *regs, u32 token)
 {
        return false;

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 25dd126..8eb91dc 100644 (file)
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -38,6 +38,7 @@
 #include <asm/tlb.h>
 #include <asm/cpuidle_haltpoll.h>
 #include <asm/ptrace.h>
+#include <asm/reboot.h>
 #include <asm/svm.h>
 
 DEFINE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
@@ -375,6 +376,14 @@ static void kvm_pv_disable_apf(void)
        pr_info("disable async PF for cpu %d\n", 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)
 {
        /*
@@ -417,14 +426,6 @@ 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);
@@ -452,13 +453,14 @@ static void __init sev_map_percpu_data(void)
        }
 }
 
-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();
 }
 
@@ -661,7 +663,7 @@ static int kvm_cpu_down_prepare(unsigned int cpu)
        unsigned long flags;
 
        local_irq_save(flags);
-       kvm_guest_cpu_offline();
+       kvm_guest_cpu_offline(false);
        local_irq_restore(flags);
        return 0;
 }
@@ -670,7 +672,7 @@ static int kvm_cpu_down_prepare(unsigned int cpu)
 
 static int kvm_suspend(void)
 {
-       kvm_guest_cpu_offline();
+       kvm_guest_cpu_offline(false);
 
        return 0;
 }
@@ -685,6 +687,20 @@ static struct syscore_ops kvm_syscore_ops = {
        .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_guest_init(void)
 {
        int i;
@@ -727,6 +743,10 @@ static 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);
 
        /*

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 081686d..ad273e5 100644 (file)
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -20,7 +20,6 @@
 #include <asm/hypervisor.h>
 #include <asm/mem_encrypt.h>
 #include <asm/x86_init.h>
-#include <asm/reboot.h>
 #include <asm/kvmclock.h>
 
 static int kvmclock __initdata = 1;
@@ -203,23 +202,6 @@ static void kvm_setup_secondary_clock(void)
 }
 #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);
@@ -349,9 +331,6 @@ 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();
 
        /*