On Mon, 19 Aug 2024, Vincent Donnefort wrote: > On Tue, Jun 11, 2024 at 07:22:03PM +0100, Matthew Wilcox wrote: > > On Tue, Jun 11, 2024 at 11:06:22AM -0700, Andrew Morton wrote: ... > > > You know what I'm going to ask ;) I'm assuming that the runtime effects > > > are "small performance optimization" and that "should we backport the > > > fix" is "no". > > > > We're going to stop using PMDs to map large folios unless the fault is > > within the first 4KiB of the PMD. No idea how many workloads that > > affects, but it only needs to be backported as far as v6.8, so we > > may as well backport it. > > Hi, I am reviving this thread after noticing this comment attached > to the fix. > > If you intend to install PTE level mappings for faults that happen outside of > the first 4KiB, I believe this will make THP support for KVM ineffective. You can relax, it's okay: where Matthew wrote "We're going to stop...", he was describing the runtime effects of the bug (now fixed) to Andrew, not proposing to make a change to mess up THP support. The fix was backported to v6.9.N, but was too late for v6.8.N EOL. Hugh
