Commit ca2fd060 authored by Claudio Imbrenda's avatar Claudio Imbrenda Committed by Janosch Frank
Browse files

KVM: s390: pv: add mmu_notifier 



Add an mmu_notifier for protected VMs. The callback function is
triggered when the mm is torn down, and will attempt to convert all
protected vCPUs to non-protected. This allows the mm teardown to use
the destroy page UVC instead of export.

Also make KVM select CONFIG_MMU_NOTIFIER, needed to use mmu_notifiers.

Signed-off-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: default avatarJanosch Frank <frankja@linux.ibm.com>
Reviewed-by: default avatarNico Boehr <nrb@linux.ibm.com>
Link: https://lore.kernel.org/r/20220628135619.32410-10-imbrenda@linux.ibm.com


Message-Id: <20220628135619.32410-10-imbrenda@linux.ibm.com>
[frankja@linux.ibm.com: Conflict resolution for mmu_notifier.h include
and struct kvm_s390_pv]
Signed-off-by: default avatarJanosch Frank <frankja@linux.ibm.com>
parent be48d86f

arch/s390/include/asm/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/seqlock.h>

#include <linux/module.h>

#include <linux/pci.h>

#include <linux/mmu_notifier.h>

#include <asm/debug.h>

#include <asm/cpu.h>

#include <asm/fpu/api.h>
@@ -929,6 +930,7 @@ struct kvm_s390_pv { 
	unsigned long stor_base;

	void *stor_var;

	bool dumping;

	struct mmu_notifier mmu_notifier;

};



struct kvm_arch{

arch/s390/kvm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ config KVM 
	select SRCU

	select KVM_VFIO

	select INTERVAL_TREE

	select MMU_NOTIFIER

	help

	  Support hosting paravirtualized guest machines using the SIE

	  virtualization capability on the mainframe. This should work

arch/s390/kvm/kvm-s390.c

+10 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 
#include <linux/sched/signal.h>

#include <linux/string.h>

#include <linux/pgtable.h>

#include <linux/mmu_notifier.h>



#include <asm/asm-offsets.h>

#include <asm/lowcore.h>
@@ -3198,6 +3199,15 @@ void kvm_arch_destroy_vm(struct kvm *kvm) 
	 */

	if (kvm_s390_pv_get_handle(kvm))

		kvm_s390_pv_deinit_vm(kvm, &rc, &rrc);

	/*

	 * Remove the mmu notifier only when the whole KVM VM is torn down,

	 * and only if one was registered to begin with. If the VM is

	 * currently not protected, but has been previously been protected,

	 * then it's possible that the notifier is still registered.

	 */

	if (kvm->arch.pv.mmu_notifier.ops)

		mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);



	debug_unregister(kvm->arch.dbf);

	free_page((unsigned long)kvm->arch.sie_page2);

	if (!kvm_is_ucontrol(kvm))

arch/s390/kvm/pv.c

+26 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <asm/mman.h>

#include <linux/pagewalk.h>

#include <linux/sched/mm.h>

#include <linux/mmu_notifier.h>

#include "kvm-s390.h"



static void kvm_s390_clear_pv_state(struct kvm *kvm)
@@ -188,6 +189,26 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc) 
	return -EIO;

}



static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,

					     struct mm_struct *mm)

{

	struct kvm *kvm = container_of(subscription, struct kvm, arch.pv.mmu_notifier);

	u16 dummy;



	/*

	 * No locking is needed since this is the last thread of the last user of this

	 * struct mm.

	 * When the struct kvm gets deinitialized, this notifier is also

	 * unregistered. This means that if this notifier runs, then the

	 * struct kvm is still valid.

	 */

	kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);

}



static const struct mmu_notifier_ops kvm_s390_pv_mmu_notifier_ops = {

	.release = kvm_s390_pv_mmu_notifier_release,

};



int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)

{

	struct uv_cb_cgc uvcb = {
@@ -229,6 +250,11 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc) 
		return -EIO;

	}

	kvm->arch.gmap->guest_handle = uvcb.guest_handle;

	/* Add the notifier only once. No races because we hold kvm->lock */

	if (kvm->arch.pv.mmu_notifier.ops != &kvm_s390_pv_mmu_notifier_ops) {

		kvm->arch.pv.mmu_notifier.ops = &kvm_s390_pv_mmu_notifier_ops;

		mmu_notifier_register(&kvm->arch.pv.mmu_notifier, kvm->mm);

	}

	return 0;

}