On 12.01.2026 12:24, Jan Beulich wrote: > On 12.01.2026 12:18, Andrew Cooper wrote: >> On 12/01/2026 11:09 am, Jan Beulich wrote: >>> On 09.01.2026 19:28, Petr Beneš wrote: >>>> From: Petr Beneš <[email protected]> >>>> >>>> Commit 7e5b662 fixed p2m_altp2m_get_or_propagate() to use the altp2m's >>>> default_access when propagating entries from the host p2m. However, the >>>> same >>>> fix was not applied to altp2m_get_effective_entry(), which has the same >>>> issue. >>>> >>>> When altp2m_get_effective_entry() prepopulates a superpage from the host >>>> p2m, it incorrectly uses the host p2m's access permissions instead of >>>> the altp2m's default_access. This causes problems when the superpage is >>>> later split (e.g., when setting mem_access on a specific 4K page): all >>>> 512 entries inherit the host p2m's access rights instead of the altp2m's >>>> default_access. >>>> >>>> This issue became apparent after commit 50baf2d, which causes the host p2m >>>> to use superpages more frequently. Before that commit, the host p2m >>>> typically had 4K entries after VM restore, so the prepopulate branch was >>>> rarely taken. >>>> >>>> Symptoms include memory-access events firing for unexpected pages when >>>> using VMI tools with altp2m, particularly after VM resume. >>>> The issue can be worked around by booting with "hap_1gb=0 hap_2mb=0". >>>> >>>> Fixes: 7e5b662 ("x86/altp2m: p2m_altp2m_get_or_propagate() should honor >>>> ap2m->default_access") >>> You didn't even Cc Tamas, who I think once again will need to ack this. >>> Already with the referenced change I didn't quite understand the >>> reasoning. >>> >>> However, two formal points: Please use 12-digit hashes, as demanded by >>> sending-patches.pandoc. Plus I don't think Fixes: is quite right here. >>> That earlier change of yours didn't mean to do more than it did, by its >>> title and description. We relatively recently introduced Amends:, which >>> may be a suitable fit here. >> >> I beg your pardon? Fixes are and Amends are synonyms. > > This is news to me. To me a "fix" addresses a bug in the referenced commit. > Whereas making a related change which isn't strictly a bugfix to the > referenced earlier change is what Amends: was introduced for. If both were > synonyms, why would you not have objected to the introduction of Amends:?
Having thought about this some more, would Complements: or Supplements: possibly better suit you? Jan
