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Peter Anvin" , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Andrew Cooper X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1751056201982325939?= X-GMAIL-MSGID: =?utf-8?q?1751056201982325939?= Provide dedicated helpers to (un)register virt hooks used during an emergency crash/reboot, and WARN if there is an attempt to overwrite the registered callback, or an attempt to do an unpaired unregister. Opportunsitically use rcu_assign_pointer() instead of RCU_INIT_POINTER(), mainly so that the set/unset paths are more symmetrical, but also because any performance gains from using RCU_INIT_POINTER() are meaningless for this code. Signed-off-by: Sean Christopherson --- arch/x86/include/asm/reboot.h | 5 +++-- arch/x86/kernel/reboot.c | 30 ++++++++++++++++++++++++------ arch/x86/kvm/vmx/vmx.c | 6 ++---- 3 files changed, 29 insertions(+), 12 deletions(-) diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h index 33c8e911e0de..1d098a7d329a 100644 --- a/arch/x86/include/asm/reboot.h +++ b/arch/x86/include/asm/reboot.h @@ -26,8 +26,9 @@ void __noreturn machine_real_restart(unsigned int type); #define MRR_APM 1 #if IS_ENABLED(CONFIG_KVM_INTEL) -typedef void crash_vmclear_fn(void); -extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss; +typedef void (cpu_emergency_virt_cb)(void); +void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback); +void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callback); #endif void cpu_emergency_disable_virtualization(void); diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index 6c0b1634b884..78182b2969db 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -795,17 +795,35 @@ void machine_crash_shutdown(struct pt_regs *regs) * * protected by rcu. */ -crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss; -EXPORT_SYMBOL_GPL(crash_vmclear_loaded_vmcss); +static cpu_emergency_virt_cb __rcu *cpu_emergency_virt_callback; + +void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback) +{ + if (WARN_ON_ONCE(rcu_access_pointer(cpu_emergency_virt_callback))) + return; + + rcu_assign_pointer(cpu_emergency_virt_callback, callback); +} +EXPORT_SYMBOL_GPL(cpu_emergency_register_virt_callback); + +void cpu_emergency_unregister_virt_callback(cpu_emergency_virt_cb *callback) +{ + if (WARN_ON_ONCE(rcu_access_pointer(cpu_emergency_virt_callback) != callback)) + return; + + rcu_assign_pointer(cpu_emergency_virt_callback, NULL); + synchronize_rcu(); +} +EXPORT_SYMBOL_GPL(cpu_emergency_unregister_virt_callback); static inline void cpu_crash_vmclear_loaded_vmcss(void) { - crash_vmclear_fn *do_vmclear_operation = NULL; + cpu_emergency_virt_cb *callback; rcu_read_lock(); - do_vmclear_operation = rcu_dereference(crash_vmclear_loaded_vmcss); - if (do_vmclear_operation) - do_vmclear_operation(); + callback = rcu_dereference(cpu_emergency_virt_callback); + if (callback) + callback(); rcu_read_unlock(); } #endif diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 7ea020456dd0..6e0cc4d03884 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -8526,8 +8526,7 @@ static void __vmx_exit(void) { allow_smaller_maxphyaddr = false; - RCU_INIT_POINTER(crash_vmclear_loaded_vmcss, NULL); - synchronize_rcu(); + cpu_emergency_unregister_virt_callback(crash_vmclear_local_loaded_vmcss); vmx_cleanup_l1d_flush(); } @@ -8577,8 +8576,7 @@ static int __init vmx_init(void) pi_init_cpu(cpu); } - rcu_assign_pointer(crash_vmclear_loaded_vmcss, - crash_vmclear_local_loaded_vmcss); + cpu_emergency_register_virt_callback(crash_vmclear_local_loaded_vmcss); vmx_check_vmcs12_offsets();