On 4/19/21 11:10 AM, Andy Lutomirski wrote: > I’m confused by this scenario. This should only affect physical pages > that are in the 2M area that contains guest memory. But, if we have a > 2M direct map PMD entry that contains kernel data and guest private > memory, we’re already in a situation in which the kernel touching > that memory would machine check, right?
Not machine check, but page fault. Do machine checks even play a special role in SEV-SNP? I thought that was only TDX? My point was just that you can't _easily_ do the 2M->4k kernel mapping demotion in a page fault handler, like I think Borislav was suggesting. > ISTM we should fully unmap any guest private page from the kernel and > all host user pagetables before actually making it be a guest private > page. Yes, that sounds attractive. Then, we'd actually know if the host kernel was doing stray reads somehow because we'd get a fault there too.