On Mon, Jan 20, 2025, Christoph Schlameuss wrote: > On Sat Jan 11, 2025 at 1:20 AM CET, Sean Christopherson wrote: > > Add a dedicated API for setting internal memslots, and have it explicitly > > disallow setting userspace memslots. Setting a userspace memslots without > > a direct command from userspace would result in all manner of issues. > > > > No functional change intended. > > > > Cc: Tao Su <tao1.su@xxxxxxxxxxxxxxx> > > Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> > > Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx> > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > > --- > > arch/x86/kvm/x86.c | 2 +- > > include/linux/kvm_host.h | 4 ++-- > > virt/kvm/kvm_main.c | 15 ++++++++++++--- > > 3 files changed, 15 insertions(+), 6 deletions(-) > > [...] > > > +int kvm_set_internal_memslot(struct kvm *kvm, > > + const struct kvm_userspace_memory_region2 *mem) > > +{ > > + if (WARN_ON_ONCE(mem->slot < KVM_USER_MEM_SLOTS)) > > + return -EINVAL; > > + > > Looking at Claudios changes I found that this is missing to acquire the > slots_lock here. > > guard(mutex)(&kvm->slots_lock); It's not missing. As of this patch, x86 is the only user of KVM-internal memslots, and x86 acquires slots_lock outside of kvm_set_internal_memslot() because x86 can have multiple address spaces (regular vs SMM) and KVM's internal memslots need to be created for both, i.e. it's desirable to holds slots_lock in the caller. If it's annoying for s390 to acquire slots_lock, we could add a wrapper, i.e. turn this into __kvm_set_internal_memslot() and then re-add kvm_set_internal_memslot() as a version that acquires and releases slots_lock.