KVM: arm64: Top up stage-2 memcache for dirty logging faults

Browse source

Dirty logging forces new stage-2 mappings to page size but does not
always split an existing block first (eager splitting is best effort
and off by default). A non-write permission fault on such a block, an
instruction fetch, still needs a page-table page to split it, but the
top-up is gated on write faults.

With the cache empty, kvm_mmu_memory_cache_alloc() hits its
guest-triggerable WARN_ON(!nobjs) and falls back to a GFP_ATOMIC
allocation under mmu_lock, with a BUG_ON() if that fails.

Top up the memcache for any permission fault while dirty logging is
active.

Fixes: 6f745f1bb5 ("KVM: arm64: Convert user_mem_abort() to generic page-table API")
Link: https://lore.kernel.org/all/20260623165634.699011F000E9@smtp.kernel.org/
Signed-off-by: Bradley Morgan <include@grrlz.net>
[tabba: reword the commit message for the generic, non-pKVM failure mode]
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Tested-by: Bradley Morgan <include@grrlz.net> # On pixel 7, Android 17 CP2A.260705.006
Test: Bradley Morgan <include@grrlz.net> # On QEMU arm64 host
Link: https://patch.msgid.link/20260717130317.1953574-4-fuad.tabba@linux.dev
Signed-off-by: Oliver Upton <oupton@kernel.org>

...

This commit is contained in:

Bradley Morgan 2026-07-17 14:03:13 +01:00 • committed by Oliver Upton

parent 6bf0215c56

commit 56fd1fc526

1 changed files with 2 additions and 3 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

5

arch/arm64/kvm/mmu.c

View file