On Mon, Jan 23, 2023 at 10:41:18AM -0800, David Matlack wrote: > On Fri, Jan 20, 2023 at 12:04:04PM -0800, Ben Gardon wrote: > > On Fri, Jan 20, 2023 at 6:34 AM Ricardo Koller <ricarkol@xxxxxxxxxx> wrote: > > > > > ... > > > > > > > + > > > > > > > + run_test(&p); > > > > > > > > > > > > Use for_each_guest_mode() to run against all supported guest modes. > > > > > > > > > > I'm not sure that would actually improve coverage. None of the page > > > > > splitting behavior depends on the mode AFAICT. > > > > > > > > You need to use for_each_guest_mode() for the ARM case. The issue is > > > > that whatever mode (guest page size and VA size) you pick might not be > > > > supported by the host. So, you first to explore what's available (via > > > > for_each_guest_mode()). > > > > > > Actually, that's fixed by using the default mode, which picks the > > > first available > > > mode. I would prefer to use for_each_guest_mode() though, who knows and > > > something fails with some specific guest page size for some reason. > > > > Okay, will do. I wasn't sure if we did eager page splitting on ARM, so > > Ricardo is in the process of upstreaming eager page splitting for ARM: > > https://lore.kernel.org/kvm/20230113035000.480021-1-ricarkol@xxxxxxxxxx/ > > > I was only planning on making this test for x86_64 initially, hence it > > being in that directory. If ARM rolls with the same behavior, then > > I'll add the for_each_mode bit and move the test up a directory. > > In addition to for_each_guest_mode(), KVM/ARM will need to expose page > size stats so the test can verify the splitting (yet another reason to > have a common MMU). > > Ricardo, if you're interested in adding page size stats to KVM/ARM ahead > of the Common MMU, e.g. to test eager page splitting, let me know. Sure, I can do that. Sounds pretty useful too. > I > want to make sure we align on the userspace-visible stat names to avoid > churn down the road. Specifically, do we want to expose neutral names > like pages_{pte,pmd,pud} or expand the KVM/x86 list to include all of > ARM's possible pages sizes like pages_{4k,16k,64k,...} (or both)? I would prefer the latter, mainly to match the x86 names: + stats->pages_4k = vm_get_stat(vm, "pages_4k"); + stats->pages_2m = vm_get_stat(vm, "pages_2m"); + stats->pages_1g = vm_get_stat(vm, "pages_1g"); (from this patch) but pages_{pte,pmd,pud} would certainly make this test simpler as it would handle all guest page sizes: + stats->pages_pte = vm_get_stat(vm, "pages_pte");
