Commit 4059172b authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Move kvm_rebooting to x86 



Move kvm_rebooting, which is only read by x86, to KVM x86 so that it can
be moved again to core x86 code.  Add a "shutdown" arch hook to facilate
setting the flag in KVM x86, along with a pile of comments to provide more
context around what KVM x86 is doing and why.

Reviewed-by: default avatarChao Gao <chao.gao@intel.com>
Acked-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Tested-by: default avatarChao Gao <chao.gao@intel.com>
Reviewed-by: default avatarDan Williams <dan.j.williams@intel.com>
Tested-by: default avatarSagi Shahar <sagis@google.com>
Link: https://patch.msgid.link/20260214012702.2368778-2-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 11439c46

arch/x86/kvm/x86.c

+22 −0
Original line number Diff line number Diff line
@@ -700,6 +700,9 @@ static void drop_user_return_notifiers(void) 
		kvm_on_user_return(&msrs->urn);

}



__visible bool kvm_rebooting;

EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_rebooting);



/*

 * Handle a fault on a hardware virtualization (VMX or SVM) instruction.

 *
@@ -13177,6 +13180,25 @@ int kvm_arch_enable_virtualization_cpu(void) 
	return 0;

}



void kvm_arch_shutdown(void)

{

	/*

	 * Set kvm_rebooting to indicate that KVM has asynchronously disabled

	 * hardware virtualization, i.e. that errors and/or exceptions on SVM

	 * and VMX instructions are expected and should be ignored.

	 */

	kvm_rebooting = true;



	/*

	 * Ensure kvm_rebooting is visible before IPIs are sent to other CPUs

	 * to disable virtualization.  Effectively pairs with the reception of

	 * the IPI (kvm_rebooting is read in task/exception context, but only

	 * _needs_ to be read as %true after the IPI function callback disables

	 * virtualization).

	 */

	smp_wmb();

}



void kvm_arch_disable_virtualization_cpu(void)

{

	kvm_x86_call(disable_virtualization_cpu)();

arch/x86/kvm/x86.h

+1 −0
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ struct kvm_host_values { 
	u64 arch_capabilities;

};



extern bool kvm_rebooting;

void kvm_spurious_fault(void);



#define SIZE_OF_MEMSLOTS_HASHTABLE \

include/linux/kvm_host.h

+7 −1
Original line number Diff line number Diff line
@@ -1627,6 +1627,13 @@ static inline void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu) {} 
#endif



#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING

/*

 * kvm_arch_shutdown() is invoked immediately prior to forcefully disabling

 * hardware virtualization on all CPUs via IPI function calls (in preparation

 * for shutdown or reboot), e.g. to allow arch code to prepare for disabling

 * virtualization while KVM may be actively running vCPUs.

 */

void kvm_arch_shutdown(void);

/*

 * kvm_arch_{enable,disable}_virtualization() are called on one CPU, under

 * kvm_usage_lock, immediately after/before 0=>1 and 1=>0 transitions of
@@ -2313,7 +2320,6 @@ static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu) 


#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING

extern bool enable_virt_at_load;

extern bool kvm_rebooting;

#endif



extern unsigned int halt_poll_ns;

virt/kvm/kvm_main.c

+7 −7
Original line number Diff line number Diff line
@@ -5578,13 +5578,15 @@ bool enable_virt_at_load = true; 
module_param(enable_virt_at_load, bool, 0444);

EXPORT_SYMBOL_FOR_KVM_INTERNAL(enable_virt_at_load);



__visible bool kvm_rebooting;

EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_rebooting);



static DEFINE_PER_CPU(bool, virtualization_enabled);

static DEFINE_MUTEX(kvm_usage_lock);

static int kvm_usage_count;



__weak void kvm_arch_shutdown(void)

{



}



__weak void kvm_arch_enable_virtualization(void)

{
@@ -5638,10 +5640,9 @@ static int kvm_offline_cpu(unsigned int cpu) 


static void kvm_shutdown(void *data)

{

	kvm_arch_shutdown();



	/*

	 * Disable hardware virtualization and set kvm_rebooting to indicate

	 * that KVM has asynchronously disabled hardware virtualization, i.e.

	 * that relevant errors and exceptions aren't entirely unexpected.

	 * Some flavors of hardware virtualization need to be disabled before

	 * transferring control to firmware (to perform shutdown/reboot), e.g.

	 * on x86, virtualization can block INIT interrupts, which are used by
@@ -5650,7 +5651,6 @@ static void kvm_shutdown(void *data) 
	 * 100% comprehensive.

	 */

	pr_info("kvm: exiting hardware virtualization\n");

	kvm_rebooting = true;

	on_each_cpu(kvm_disable_virtualization_cpu, NULL, 1);

}