On Tue, May 04, 2021, Ben Gardon wrote: > On Tue, May 4, 2021 at 12:21 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > > > On 03/05/21 19:31, Ben Gardon wrote: > > > On Mon, May 3, 2021 at 6:45 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > >> > > >> On 29/04/21 23:18, Ben Gardon wrote: > > >>> This series enables KVM to save memory when using the TDP MMU by waiting > > >>> to allocate memslot rmaps until they are needed. To do this, KVM tracks > > >>> whether or not a shadow root has been allocated. In order to get away > > >>> with not allocating the rmaps, KVM must also be sure to skip operations > > >>> which iterate over the rmaps. If the TDP MMU is in use and we have not > > >>> allocated a shadow root, these operations would essentially be op-ops > > >>> anyway. Skipping the rmap operations has a secondary benefit of avoiding > > >>> acquiring the MMU lock in write mode in many cases, substantially > > >>> reducing MMU lock contention. > > >>> > > >>> This series was tested on an Intel Skylake machine. With the TDP MMU off > > >>> and on, this introduced no new failures on kvm-unit-tests or KVM selftests. > > >> > > >> Thanks, I only reported some technicalities in the ordering of loads > > >> (which matter since the loads happen with SRCU protection only). Apart > > >> from this, this looks fine! > > > > > > Awesome to hear, thank you for the reviews. Should I send a v3 > > > addressing those comments, or did you already make those changes when > > > applying to your tree? > > > > No, I didn't (I wanted some oversight, and this is 5.14 stuff anyway). > > Ah, okay I'll send out a v3 soon, discussion on the other patches settles. I'll look through v2 this afternoon, now that I've mostly dug myself out of RDPID hell.
