x86: clear vmcss on all cpus when doing kdump if necessary

index 317ff17..d892211 100644
@@ -163,6 +163,9 @@ struct kimage_arch {
 };
 #endif
 
+extern void (*crash_clear_loaded_vmcss)(void);
+DECLARE_PER_CPU(int, vmclear_skipped);
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_X86_KEXEC_H */

index 13ad899..b9f264e 100644
@@ -16,6 +16,7 @@
 #include <linux/delay.h>
 #include <linux/elf.h>
 #include <linux/elfcore.h>
+#include <linux/module.h>
 
 #include <asm/processor.h>
 #include <asm/hardirq.h>

@@ -30,6 +31,27 @@
 
 int in_crash_kexec;
 
+/*
+ * This is used to VMCLEAR vmcss loaded on all
+ * cpus. And when loading kvm_intel module, the
+ * function pointer will be made valid.
+ */
+void (*crash_clear_loaded_vmcss)(void) = NULL;
+EXPORT_SYMBOL_GPL(crash_clear_loaded_vmcss);
+
+DEFINE_PER_CPU(int, vmclear_skipped) = 1;
+EXPORT_SYMBOL_GPL(vmclear_skipped);
+
+static void cpu_emergency_clear_loaded_vmcss(void)
+{
+	int cpu = raw_smp_processor_id();
+	int skipped;
+
+	skipped = per_cpu(vmclear_skipped, cpu);
+	if (!skipped && crash_clear_loaded_vmcss)
+		crash_clear_loaded_vmcss();
+}
+
 #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
 
 static void kdump_nmi_callback(int cpu, struct pt_regs *regs)

@@ -46,6 +68,11 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
 #endif
 	crash_save_cpu(regs, cpu);
 
+	/*
+	 * VMCLEAR vmcss loaded on all cpus if needed.
+	 */
+	cpu_emergency_clear_loaded_vmcss();
+
 	/* Disable VMX or SVM if needed.
 	 *
 	 * We need to disable virtualization on all CPUs.

@@ -88,6 +115,11 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 
 	kdump_nmi_shootdown_cpus();
 
+	/*
+	 * VMCLEAR vmcss loaded on this cpu if needed.
+	 */
+	cpu_emergency_clear_loaded_vmcss();
+
 	/* Booting kdump kernel with VMX or SVM enabled won't work,
 	 * because (among other limitations) we can't disable paging
 	 * with the virt flags.

index 4ff0ab9..029ec7b 100644
@@ -41,6 +41,7 @@
 #include <asm/i387.h>
 #include <asm/xcr.h>
 #include <asm/perf_event.h>
+#include <asm/kexec.h>
 
 #include "trace.h"
 

@@ -963,6 +964,20 @@ static void vmcs_load(struct vmcs *vmcs)
 		       vmcs, phys_addr);
 }
 
+static inline void enable_vmclear_in_kdump(int cpu)
+{
+#ifdef CONFIG_KEXEC
+	per_cpu(vmclear_skipped, cpu) = 0;
+#endif
+}
+
+static inline void disable_vmclear_in_kdump(int cpu)
+{
+#ifdef CONFIG_KEXEC
+	per_cpu(vmclear_skipped, cpu) = 1;
+#endif
+}
+
 static void __loaded_vmcs_clear(void *arg)
 {
 	struct loaded_vmcs *loaded_vmcs = arg;

@@ -972,8 +987,10 @@ static void __loaded_vmcs_clear(void *arg)
 		return; /* vcpu migration can race with cpu offline */
 	if (per_cpu(current_vmcs, cpu) == loaded_vmcs->vmcs)
 		per_cpu(current_vmcs, cpu) = NULL;
+	disable_vmclear_in_kdump(cpu);
 	list_del(&loaded_vmcs->loaded_vmcss_on_cpu_link);
 	loaded_vmcs_init(loaded_vmcs);
+	enable_vmclear_in_kdump(cpu);
 }
 
 static void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs)

@@ -1491,8 +1508,10 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 
 		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 		local_irq_disable();
+		disable_vmclear_in_kdump(cpu);
 		list_add(&vmx->loaded_vmcs->loaded_vmcss_on_cpu_link,
 			 &per_cpu(loaded_vmcss_on_cpu, cpu));
+		enable_vmclear_in_kdump(cpu);
 		local_irq_enable();
 
 		/*

@@ -2302,6 +2321,9 @@ static int hardware_enable(void *garbage)
 		return -EBUSY;
 
 	INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu));
+
+	enable_vmclear_in_kdump(cpu);
+
 	rdmsrl(MSR_IA32_FEATURE_CONTROL, old);
 
 	test_bits = FEATURE_CONTROL_LOCKED;

@@ -2333,6 +2355,8 @@ static void vmclear_local_loaded_vmcss(void)
 	list_for_each_entry_safe(v, n, &per_cpu(loaded_vmcss_on_cpu, cpu),
 				 loaded_vmcss_on_cpu_link)
 		__loaded_vmcs_clear(v);
+
+	disable_vmclear_in_kdump(cpu);
 }
 
 

@@ -7230,6 +7254,10 @@ static int __init vmx_init(void)
 	if (r)
 		goto out3;
 
+#ifdef CONFIG_KEXEC
+	crash_clear_loaded_vmcss = vmclear_local_loaded_vmcss;
+#endif
+
 	vmx_disable_intercept_for_msr(MSR_FS_BASE, false);
 	vmx_disable_intercept_for_msr(MSR_GS_BASE, false);
 	vmx_disable_intercept_for_msr(MSR_KERNEL_GS_BASE, true);

@@ -7265,6 +7293,10 @@ static void __exit vmx_exit(void)
 	free_page((unsigned long)vmx_io_bitmap_b);
 	free_page((unsigned long)vmx_io_bitmap_a);
 
+#ifdef CONFIG_KEXEC
+	crash_clear_loaded_vmcss = NULL;
+#endif
+
 	kvm_exit();
 }