On Thu, Nov 02, 2023, Fuad Tabba wrote: > Hi, > > On Fri, Oct 27, 2023 at 7:22 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > > > Add flags to "struct kvm_gfn_range" to let notifier events target only > > shared and only private mappings, and write up the existing mmu_notifier > > events to be shared-only (private memory is never associated with a > > userspace virtual address, i.e. can't be reached via mmu_notifiers). > > > > Add two flags so that KVM can handle the three possibilities (shared, > > private, and shared+private) without needing something like a tri-state > > enum. > > > > Link: https://lore.kernel.org/all/ZJX0hk+KpQP0KUyB@xxxxxxxxxx > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > > --- > > include/linux/kvm_host.h | 2 ++ > > virt/kvm/kvm_main.c | 7 +++++++ > > 2 files changed, 9 insertions(+) > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 96aa930536b1..89c1a991a3b8 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -263,6 +263,8 @@ struct kvm_gfn_range { > > gfn_t start; > > gfn_t end; > > union kvm_mmu_notifier_arg arg; > > + bool only_private; > > + bool only_shared; > > If these flags aren't used in this patch series, should this patch be > moved to the other series? If *both* TDX and SNP need this patch, then I think it's probably worth applying it now to make their lives easier. But if only one needs the support, then I completely agree this should be punted to whichever series needs it (this also came up in v11, but we didn't force the issue). Mike, Isaku? > Also, if shared+private is a possibility, doesn't the prefix "only_" > confuse things a bit? I.e., what is shared+private, is it when both > are 0 or when both are 1? I assume it's the former (both are 0), but > it might be clearer. Heh, I was hoping that "only_private && only_shared" would be obviously nonsensical. The only alternative I can think would be to add an enum, e.g. enum { PROCESS_PRIVATE_AND_SHARED, PROCESS_ONLY_PRIVATE, PROCESS_ONLY_SHARED, }; because every other way of expressing the flags either results in more confusion or an unsafe default. I.e. I want zapping only private or only shared to require the caller to explicitly set a non-zero value, which is how I ended up with "only_{private,shared}" as opposed to "process_{private,shared}".
