On Thu, Dec 22, 2022 at 01:26:25PM +0100, Borislav Petkov wrote: > On Wed, Dec 14, 2022 at 01:39:54PM -0600, Michael Roth wrote: > > This mainly indicates to KVM that it should expect all private guest > > memory to be backed by private memslots. Ideally this would work > > similarly for others archs, give or take a few additional flags, but > > for now it's a simple boolean indicator for x86. > > ... > > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > > index c7e9d375a902..cc9424ccf9b2 100644 > > --- a/include/uapi/linux/kvm.h > > +++ b/include/uapi/linux/kvm.h > > @@ -1219,6 +1219,7 @@ struct kvm_ppc_resize_hpt { > > #define KVM_CAP_DIRTY_LOG_RING_ACQ_REL 223 > > #define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 224 > > #define KVM_CAP_MEMORY_ATTRIBUTES 225 > > +#define KVM_CAP_UNMAPPED_PRIVATE_MEM 240 > > Isn't this new cap supposed to be documented somewhere in > Documentation/virt/kvm/api.rst ? It should, but this is sort of a placeholder for now. Ideally we'd re-use the capabilities introduced by UPM patchset rather than introduce a new one. Originally the UPM patchset had a KVM_CAP_PRIVATE_MEM which we planned to use to switch between legacy SEV and UPM-based SEV (for lazy-pinning support) by making it writeable, but that was removed in v10 in favor of KVM_CAP_MEMORY_ATTRIBUTES, which is tied to the new KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES/KVM_SET_MEMORY_ATTRIBUTES ioctls: https://lore.kernel.org/lkml/CA+EHjTxXOdzcP25F57Mtmnb1NWyG5DcyqeDPqzjEOzRUrqH8FQ@xxxxxxxxxxxxxx/ It wasn't clear at the time if that was the right interface to use for this particular case, so we stuck with the more general 'use-upm/dont-use-upm' semantics originally provided by making KVM_CAP_UNMAPPED_PRIVATE_MEM/KVM_CAP_PRIVATE_MEM writeable. But maybe it's okay to just make KVM_CAP_MEMORY_ATTRIBUTES writeable and require userspace to negotiate it rather than just tying it to CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES. Or maybe introducing a new KVM_SET_SUPPORTED_MEMORY_ATTRIBUTES ioctl to pair with KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES. It sort of makes sense, since userspace needs to be prepared to deal with KVM_EXIT_MEMORY_FAULTs relating to these attributes. -Mike > > -- > Regards/Gruss, > Boris. > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpeople.kernel.org%2Ftglx%2Fnotes-about-netiquette&data=05%7C01%7Cmichael.roth%40amd.com%7Cb019ddcb34a74fae1e3e08dae417c322%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638073087997837943%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=QRyV96y3drt%2BqwxfifWzJ6UF6te8NOKWAFuGAYOdKcg%3D&reserved=0