KVM: arm64: Don't advertise eager page splitting under pKVM

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Under pKVM the stage-2 walker resolves to pkvm_pgtable_stage2_split(), a
WARN_ON_ONCE(1) stub, yet KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE is still
enabled and reported for non-protected guests: the capability check keys
on the per-VM protected state while the walker dispatch keys on the
host-global mode. Enabling the cap and then dirty-logging the guest
reaches the stub, splatting a userspace-reachable WARN.

Reject the capability, and stop reporting a chunk size and the
supported block sizes, for every VM once pKVM is enabled, keyed on the
host-global mode like the split dispatch. Gating only protected VMs
would leave the non-protected guests that reach the stub still able to
enable it. Userspace decides whether eager splitting is available from
the block-size bitmap (QEMU falls back to no eager splitting when it
reads 0), so leaving it advertised steers an explicit request into the
enable failure instead of the fallback.

Fixes: e912efed48 ("KVM: arm64: Introduce the EL1 pKVM MMU")
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Reviewed-by: Bradley Morgan <include@grrlz.net>
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/20260717130317.1953574-7-fuad.tabba@linux.dev
Signed-off-by: Oliver Upton <oupton@kernel.org>

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This commit is contained in:

Fuad Tabba 2026-07-17 14:03:16 +01:00 • committed by Oliver Upton

parent c243222701

commit c6f308b4d3

1 changed files with 3 additions and 0 deletions

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arch/arm64/include/asm/kvm_pkvm.h

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