On Fri, 12 Jul 2024 09:39:52 -0700 Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > > > One other issue we need to worry about is that IIUC rseq memory is > > allocated by the guest/user, not the host kernel. This means it can be > > swapped out. The code that handles this needs to be able to handle user > > page faults. > > This is a non-issue, it will Just Work, same as any other memory that is exposed > to the guest and can be reclaimed/swapped/migrated.. > > If the host swaps out the rseq page, mmu_notifiers will call into KVM and KVM will > unmap the page from the guest. If/when the page is accessed by the guest, KVM > will fault the page back into the host's primary MMU, and then map the new pfn > into the guest. My comment is that in the host kernel, the access to this memory needs to be user page fault safe. You can't call it in atomic context. -- Steve
