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: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> Acked-by: Janosch Frank <frankja@xxxxxxxxxxxxx> Reviewed-by: Nico Boehr <nrb@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220628135619.32410-10-imbrenda@xxxxxxxxxxxxx Message-Id: <20220628135619.32410-10-imbrenda@xxxxxxxxxxxxx> [frankja@xxxxxxxxxxxxx: Conflict resolution for mmu_notifier.h include and struct kvm_s390_pv] Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx> --- arch/s390/include/asm/kvm_host.h | 2 ++ arch/s390/kvm/Kconfig | 1 + arch/s390/kvm/kvm-s390.c | 10 ++++++++++ arch/s390/kvm/pv.c | 26 ++++++++++++++++++++++++++ 4 files changed, 39 insertions(+) diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index fca4fcf72a2a..6f9fc8bb0303 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -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{ diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig index 2e84d3922f7c..33f4ff909476 100644 --- a/arch/s390/kvm/Kconfig +++ b/arch/s390/kvm/Kconfig @@ -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 diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index d10c3b163cdc..5b77c43fbb01 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -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)) diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c index d18c5ccfa5dc..c063d1a9cf04 100644 --- a/arch/s390/kvm/pv.c +++ b/arch/s390/kvm/pv.c @@ -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; } -- 2.36.1
