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KVM: SEV: Mark nested locking of vcpu->lock

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[ Upstream commit 0c2c7c0692 ]

svm_vm_migrate_from() uses sev_lock_vcpus_for_migration() to lock all
source and target vcpu->locks. Unfortunately there is an 8 subclass
limit, so a new subclass cannot be used for each vCPU. Instead maintain
ownership of the first vcpu's mutex.dep_map using a role specific
subclass: source vs target. Release the other vcpu's mutex.dep_maps.

Fixes: b56639318b ("KVM: SEV: Add support for SEV intra host migration")
Reported-by: John Sperbeck<jsperbeck@google.com>
Suggested-by: David Rientjes <rientjes@google.com>
Suggested-by: Sean Christopherson <seanjc@google.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Peter Gonda <pgonda@google.com>

Message-Id: <20220502165807.529624-1-pgonda@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Peter Gonda 2022-05-02 09:58:07 -07:00 committed by Greg Kroah-Hartman
parent 71d2be7f9e
commit da6c2bd63e
1 changed files with 38 additions and 4 deletions
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42
arch/x86/kvm/svm/sev.c
View file

@ -1590,24 +1590,51 @@ static void sev_unlock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
atomic_set_release(&src_sev->migration_in_progress, 0);
}
/* vCPU mutex subclasses. */
enum sev_migration_role {
SEV_MIGRATION_SOURCE = 0,
SEV_MIGRATION_TARGET,
SEV_NR_MIGRATION_ROLES,
};
static int sev_lock_vcpus_for_migration(struct kvm *kvm)
static int sev_lock_vcpus_for_migration(struct kvm *kvm,
enum sev_migration_role role)
{
struct kvm_vcpu *vcpu;
unsigned long i, j;
bool first = true;
kvm_for_each_vcpu(i, vcpu, kvm) {
if (mutex_lock_killable(&vcpu->mutex))
if (mutex_lock_killable_nested(&vcpu->mutex, role))
goto out_unlock;
if (first) {
/*
* Reset the role to one that avoids colliding with
* the role used for the first vcpu mutex.
*/
role = SEV_NR_MIGRATION_ROLES;
first = false;
} else {
mutex_release(&vcpu->mutex.dep_map, _THIS_IP_);
}
}
return 0;
out_unlock:
first = true;
kvm_for_each_vcpu(j, vcpu, kvm) {
if (i == j)
break;
if (first)
first = false;
else
mutex_acquire(&vcpu->mutex.dep_map, role, 0, _THIS_IP_);
mutex_unlock(&vcpu->mutex);
}
return -EINTR;
@ -1617,8 +1644,15 @@ static void sev_unlock_vcpus_for_migration(struct kvm *kvm)
{
struct kvm_vcpu *vcpu;
unsigned long i;
bool first = true;
kvm_for_each_vcpu(i, vcpu, kvm) {
if (first)
first = false;
else
mutex_acquire(&vcpu->mutex.dep_map,
SEV_NR_MIGRATION_ROLES, 0, _THIS_IP_);
mutex_unlock(&vcpu->mutex);
}
}
@ -1726,10 +1760,10 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
charged = true;
}
ret = sev_lock_vcpus_for_migration(kvm);
ret = sev_lock_vcpus_for_migration(kvm, SEV_MIGRATION_SOURCE);
if (ret)
goto out_dst_cgroup;
ret = sev_lock_vcpus_for_migration(source_kvm);
ret = sev_lock_vcpus_for_migration(source_kvm, SEV_MIGRATION_TARGET);
if (ret)
goto out_dst_vcpu;