On 2/4/22 16:53, Claudio Imbrenda wrote:
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.
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
---
arch/s390/include/asm/kvm_host.h | 2 ++
arch/s390/kvm/pv.c | 20 ++++++++++++++++++++
2 files changed, 22 insertions(+)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index a22c9266ea05..1bccb8561ba9 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -19,6 +19,7 @@
#include <linux/kvm.h>
#include <linux/seqlock.h>
#include <linux/module.h>
+#include <linux/mmu_notifier.h>
#include <asm/debug.h>
#include <asm/cpu.h>
#include <asm/fpu/api.h>
@@ -921,6 +922,7 @@ struct kvm_s390_pv {
u64 guest_len;
unsigned long stor_base;
void *stor_var;
+ struct mmu_notifier mmu_notifier;
};
struct kvm_arch{
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index f1e812a45acb..d3b8fd9b5b3e 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -193,6 +193,21 @@ 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);
Are we sure that the kvm pointer is still valid at this point?
+ u16 dummy;
+
+ mutex_lock(&kvm->lock);
Against what are we locking here?
+ kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
I'd guess that we can't really have a second kvm_s390_cpus_from_pv()
call in flight, right? If the mm is being torn down there would be no
code left that can execute the IOCTL.
+ mutex_unlock(&kvm->lock);
+}
+
+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 = {
@@ -234,6 +249,11 @@ 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;
}
