On Wed, Feb 7, 2024 at 5:21 PM Andrew Cooper <[email protected]> wrote: > > On 07/02/2024 1:18 am, George Dunlap wrote: > > On Tue, Feb 6, 2024 at 6:08 PM Petr Beneš <[email protected]> wrote: > >> From: Petr Beneš <[email protected]> > >> > >> This patch addresses a behavior discrepancy in the handling of altp2m > >> views, > >> where upon the creation and subsequent EPT violation, the page access > >> permissions were incorrectly inherited from the hostp2m instead of > >> respecting > >> the altp2m default_access. > >> > >> Previously, when a new altp2m view was established with restrictive > >> default_access permissions and activated via xc_altp2m_switch_to_view(), > >> it failed to trigger an event on the first access violation. This behavior > >> diverged from the intended mechanism, where the altp2m's default_access > >> should dictate the initial permissions, ensuring proper event triggering on > >> access violations. > >> > >> The correction involves modifying the handling mechanism to respect the > >> altp2m view's default_access upon its activation, eliminating the need for > >> setting memory access permissions for the entire altp2m range (e.g. within > >> xen-access.c). This change not only aligns the behavior with the expected > >> access control logic but also results in a significant performance > >> improvement > >> by reducing the overhead associated with setting memory access permissions > >> across the altp2m range. > >> > >> Signed-off-by: Petr Beneš <[email protected]> > > Thanks Petr, this looks like a great change. > > > > Two things: > > > > - Probably worth adjusting the comment at the top of > > p2m_altp2m_get_or_propagate to mention that you use the altp2m > > default_access when propagating from the host p2m > > > > - This represents a change in behavior, so probably at least worth a > > mention in CHANGELOG.md? > > This is a bugfix to an tech preview feature. It's not remotely close to > CHANGELOG material. > > Tangent. SUPPORT.md says tech preview on ARM, despite there being no > support in the slightest. Patches were posted and never taken. > > > Tamas, I guess this is OK from an interface compatibility point of > > view? In theory it should always have been behaving this way. > > Given the already-provided Ack, I expect that has been considered and > deemed ok.
Correct, this is just a bugfix. Tamas
