On Wed, Jul 18, 2018 at 04:38:02PM -0700, Dave Hansen wrote: > On 07/17/2018 04:20 AM, Kirill A. Shutemov wrote: > > Store KeyID in bits 31:16 of extended page flags. These bits are unused. > > I'd love a two sentence remind of what page_ext is and why you chose to > use it. Yes, you need this. No, not everybody that you want to review > this patch set knows what it is or why you chose it. Okay. > > page_keyid() returns zero until page_ext is ready. > > Is there any implication of this? Or does it not matter because we > don't run userspace until after page_ext initialization is done? It matters in sense that we shouldn't reference page_ext before it's initialized otherwise we will get garbage and crash. > > page_ext initializer enables static branch to indicate that > > "enables a static branch" > > > page_keyid() can use page_ext. The same static branch will gate MKTME > > readiness in general. > > Can you elaborate on this a bit? It would also be a nice place to hint > to the folks working hard on the APIs to ensure she checks this. Okay. > > We don't yet set KeyID for the page. It will come in the following > > patch that implements prep_encrypted_page(). All pages have KeyID-0 for > > now. > > It also wouldn't hurt to mention why you don't use an X86_FEATURE_* for > this rather than an explicit static branch. I'm sure the x86 > maintainers will be curious. Sure. -- Kirill A. Shutemov
