| Date | Fri, 21 Jul 2023 12:57:07 +0200 | Subject | Re: [RFC PATCH v11 08/29] KVM: Introduce per-page memory attributes | From | Paolo Bonzini <> |
| |
On 7/19/23 01:44, Sean Christopherson wrote: > From: Chao Peng <chao.p.peng@linux.intel.com> > > In confidential computing usages, whether a page is private or shared is > necessary information for KVM to perform operations like page fault > handling, page zapping etc. There are other potential use cases for > per-page memory attributes, e.g. to make memory read-only (or no-exec, > or exec-only, etc.) without having to modify memslots. > > Introduce two ioctls (advertised by KVM_CAP_MEMORY_ATTRIBUTES) to allow > userspace to operate on the per-page memory attributes. > - KVM_SET_MEMORY_ATTRIBUTES to set the per-page memory attributes to > a guest memory range. > - KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES to return the KVM supported > memory attributes. > > Use an xarray to store the per-page attributes internally, with a naive, > not fully optimized implementation, i.e. prioritize correctness over > performance for the initial implementation. > > Because setting memory attributes is roughly analogous to mprotect() on > memory that is mapped into the guest, zap existing mappings prior to > updating the memory attributes. Opportunistically provide an arch hook > for the post-set path (needed to complete invalidation anyways) in > anticipation of x86 needing the hook to update metadata related to > determining whether or not a given gfn can be backed with various sizes > of hugepages. > > It's possible that future usages may not require an invalidation, e.g. > if KVM ends up supporting RWX protections and userspace grants _more_ > protections, but again opt for simplicity and punt optimizations to > if/when they are needed. > > Suggested-by: Sean Christopherson <seanjc@google.com> > Link: https://lore.kernel.org/all/Y2WB48kD0J4VGynX@google.com > Cc: Fuad Tabba <tabba@google.com> > Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com> > Co-developed-by: Sean Christopherson <seanjc@google.com> > Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
|