x86/reboot: VMCLEAR active VMCSes before emergency reboot

[ Upstream commit b23c83ad2c638420ec0608a9de354507c41bec29 ]

VMCLEAR active VMCSes before any emergency reboot, not just if the kernel
may kexec into a new kernel after a crash.  Per Intel's SDM, the VMX
architecture doesn't require the CPU to flush the VMCS cache on INIT.  If
an emergency reboot doesn't RESET CPUs, cached VMCSes could theoretically
be kept and only be written back to memory after the new kernel is booted,
i.e. could effectively corrupt memory after reboot.

Opportunistically remove the setting of the global pointer to NULL to make
checkpatch happy.

Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>
Link: https://lore.kernel.org/r/20230721201859.2307736-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index a3760ca796aa24c6976231fc1485ceb31d3c5185..256eee99afc8f9f75a1c7e6f707c1a5fb2cbe1b6 100644 (file)
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -208,8 +208,6 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image);
 #endif
 #endif
 
-typedef void crash_vmclear_fn(void);
-extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
 extern void kdump_nmi_shootdown_cpus(void);
 
 #endif /* __ASSEMBLY__ */

diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h
index bc5b4d788c08dbc8f47bb8d72c7f267982e716e6..2551baec927d2e809dd0b742bc36bb71fe527154 100644 (file)
--- a/arch/x86/include/asm/reboot.h
+++ b/arch/x86/include/asm/reboot.h
@@ -25,6 +25,8 @@ void __noreturn machine_real_restart(unsigned int type);
 #define MRR_BIOS       0
 #define MRR_APM                1
 
+typedef void crash_vmclear_fn(void);
+extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
 void cpu_emergency_disable_virtualization(void);
 
 typedef void (*nmi_shootdown_cb)(int, struct pt_regs*);

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index cdd92ab43cda4babc8783ce05216273298e5472e..54cd959cb316030799de57d55823be0b388b8f26 100644 (file)
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -48,38 +48,12 @@ struct crash_memmap_data {
        unsigned int type;
 };
 
-/*
- * This is used to VMCLEAR all VMCSs loaded on the
- * processor. And when loading kvm_intel module, the
- * callback function pointer will be assigned.
- *
- * protected by rcu.
- */
-crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss = NULL;
-EXPORT_SYMBOL_GPL(crash_vmclear_loaded_vmcss);
-
-static inline void cpu_crash_vmclear_loaded_vmcss(void)
-{
-       crash_vmclear_fn *do_vmclear_operation = NULL;
-
-       rcu_read_lock();
-       do_vmclear_operation = rcu_dereference(crash_vmclear_loaded_vmcss);
-       if (do_vmclear_operation)
-               do_vmclear_operation();
-       rcu_read_unlock();
-}
-
 #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
 
 static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
 {
        crash_save_cpu(regs, cpu);
 
-       /*
-        * VMCLEAR VMCSs loaded on all cpus if needed.
-        */
-       cpu_crash_vmclear_loaded_vmcss();
-
        /*
         * Disable Intel PT to stop its logging
         */
@@ -133,11 +107,6 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 
        crash_smp_send_stop();
 
-       /*
-        * VMCLEAR VMCSs loaded on this cpu if needed.
-        */
-       cpu_crash_vmclear_loaded_vmcss();
-
        cpu_emergency_disable_virtualization();
 
        /*

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index d03c551defccf03336a1276a97d7c79267cbb212..299b970e5f8299b50aed30ac373749a9bb869b08 100644 (file)
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -787,6 +787,26 @@ void machine_crash_shutdown(struct pt_regs *regs)
 }
 #endif
 
+/*
+ * This is used to VMCLEAR all VMCSs loaded on the
+ * processor. And when loading kvm_intel module, the
+ * callback function pointer will be assigned.
+ *
+ * protected by rcu.
+ */
+crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
+EXPORT_SYMBOL_GPL(crash_vmclear_loaded_vmcss);
+
+static inline void cpu_crash_vmclear_loaded_vmcss(void)
+{
+       crash_vmclear_fn *do_vmclear_operation = NULL;
+
+       rcu_read_lock();
+       do_vmclear_operation = rcu_dereference(crash_vmclear_loaded_vmcss);
+       if (do_vmclear_operation)
+               do_vmclear_operation();
+       rcu_read_unlock();
+}
 
 /* This is the CPU performing the emergency shutdown work. */
 int crashing_cpu = -1;
@@ -798,6 +818,8 @@ int crashing_cpu = -1;
  */
 void cpu_emergency_disable_virtualization(void)
 {
+       cpu_crash_vmclear_loaded_vmcss();
+
        cpu_emergency_vmxoff();
        cpu_emergency_svm_disable();
 }

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4e972b9b68e591e098d588bc4d99fd935ab6122f..31a10d774df6dbefca3a5518c2d96fc2bdaecc88 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -40,7 +40,7 @@
 #include <asm/idtentry.h>
 #include <asm/io.h>
 #include <asm/irq_remapping.h>
-#include <asm/kexec.h>
+#include <asm/reboot.h>
 #include <asm/perf_event.h>
 #include <asm/mmu_context.h>
 #include <asm/mshyperv.h>
@@ -702,7 +702,6 @@ static int vmx_set_guest_uret_msr(struct vcpu_vmx *vmx,
        return ret;
 }
 
-#ifdef CONFIG_KEXEC_CORE
 static void crash_vmclear_local_loaded_vmcss(void)
 {
        int cpu = raw_smp_processor_id();
@@ -712,7 +711,6 @@ static void crash_vmclear_local_loaded_vmcss(void)
                            loaded_vmcss_on_cpu_link)
                vmcs_clear(v->vmcs);
 }
-#endif /* CONFIG_KEXEC_CORE */
 
 static void __loaded_vmcs_clear(void *arg)
 {
@@ -8522,10 +8520,9 @@ static void __vmx_exit(void)
 {
        allow_smaller_maxphyaddr = false;
 
-#ifdef CONFIG_KEXEC_CORE
        RCU_INIT_POINTER(crash_vmclear_loaded_vmcss, NULL);
        synchronize_rcu();
-#endif
+
        vmx_cleanup_l1d_flush();
 }
 
@@ -8598,10 +8595,9 @@ static int __init vmx_init(void)
                pi_init_cpu(cpu);
        }
 
-#ifdef CONFIG_KEXEC_CORE
        rcu_assign_pointer(crash_vmclear_loaded_vmcss,
                           crash_vmclear_local_loaded_vmcss);
-#endif
+
        vmx_check_vmcs12_offsets();
 
        /*