Re: [PATCH v3 | stable v5.10 3/3] x86/kvm: Disable all PV features on crash

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 31/05/21 16:05, Krzysztof Kozlowski wrote:
From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

commit 3d6b84132d2a57b5a74100f6923a8feb679ac2ce upstream.

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@xxxxxxxxxx>
Message-Id: <20210414123544.1060604-5-vkuznets@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxx>
---
  arch/x86/include/asm/kvm_para.h |  6 -----
  arch/x86/kernel/kvm.c           | 44 ++++++++++++++++++++++++---------
  arch/x86/kernel/kvmclock.c      | 21 ----------------
  3 files changed, 32 insertions(+), 39 deletions(-)

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 9c56e0defd45..69299878b200 100644
--- 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 be1c42e663c6..7462b79c39de 100644
--- 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("Unregister pv shared memory 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);
@@ -461,13 +462,14 @@ static bool pv_tlb_flush_supported(void)
static DEFINE_PER_CPU(cpumask_var_t, __pv_cpu_mask); -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();
  }
@@ -613,7 +615,7 @@ 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;
  }
@@ -622,7 +624,7 @@ 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;
  }
@@ -637,6 +639,20 @@ 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 kvm_flush_tlb_others(const struct cpumask *cpumask,
  			const struct flush_tlb_info *info)
  {
@@ -705,6 +721,10 @@ 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 327a0de01066..c4ac26333bc4 100644
--- 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;
@@ -204,23 +203,6 @@ 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);
@@ -350,9 +332,6 @@ 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();
/*


Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>




[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux