Map made every singly mapped section page private resident memory. A JIT
or shm_open section is file backed and committed: its bytes live in the
file, and its alias descriptors map duplicated handles, which the physical
page slots do not match, so a resident copy diverged from the file, and
committing its view on a demote failed with access denied
(guest_jit_shared_memory). Only direct memory backings, mapped through the
new GuestArenaMapDirect, now become resident; other sections keep main's
shared views. Shared pages are committed only while their section page is
reserved, as on main.
The socket host write tests map their direct memory a second time, so the
write-protected shared path they check is still the one they exercise.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V1W4jdNSKTV7xwuS6xQPJV
Writes into shared (direct) guest memory on Windows are caught by write
protecting each 16 KiB view and taking the fault. The fault reopened
and invalidated the whole view, so a collect reported all four 4 KiB
pages of a view whenever any byte of it was written, including pages
nobody wrote. A GPU surface that ends or starts inside such a view
then had its edge pages taken for CPU writes whenever the title wrote
the memory next to it, and the storage write-back kept the guest's
stale bytes there instead of the GPU's results.
Each view now keeps a write generation, a seen generation and the
write protection per 4 KiB page. A fault invalidates and reopens only
its page, a host write only the pages it covers, and a collect reports
and re-arms only the pages it covers. VirtualProtect is called once
per contiguous run of pages whose protection changes, so arming or
pinning a view takes one call when those pages are contiguous and two
when they are not. A guest store that fills a whole view takes up to
four faults instead of one.
A collect does not settle a page that it cannot write protect because
a host write is open on one of the page's views; it reports the page
again until a collect can arm it. main settled such a page and relied
on the end of the host write invalidating the whole view, so a guest
store into it during the host write was reported only after the host
write ended. With only the written pages invalidated there, the store
would not be reported at all.
A collect that runs out of room partway through a view now settles the
pages it already reported there and nothing after them; before, it
settled none of them and reported them again at the next collect.
CheckSharedWritePages writes one byte into the second 4 KiB page of a
view and requires a collect of the view's last two pages to report
nothing; main reports both. It also checks a store across two pages
and a file read into one page. CheckSharedWritesDuringHostWrite stores
into a fault-opened page of a view after a collect while a host write
is open on another page of it, and requires every collect of the view
and of its alias to report that page until the host write has ended.
agc_shared_write_partial_collect resets the two interior pages of a
view after writes to all four and requires the outer two to stay
pending. The existing shared-memory checks in guest_memory,
agc_shared_write_partial_collect and guest_socket_host_write (the
recvfrom sender outputs) now expect the pages written instead of the
whole view.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
thibaut
fdfawef324
Ondra97