Arm CPUs support some subset of the granule (page) sizes 4K, 16K and 64K. The guest selects the one it wants using bits in the TCR_ELx registers. If it tries to program these registers with a value that is either reserved or which requests a size that the CPU does not implement, the architecture requires that the CPU behaves as if the field was programmed to some size that has been implemented. Currently we don't implement this, and instead let the guest use any granule size, even if the CPU ID register fields say it isn't present.
Patch 1 in this series makes us enforce this architectural requirement (the main effect will be that we stop incorrectly implementing 16K granules on most of the non-cpu-max CPUs). Patch 2 adds FEAT_GTG to the list of supported features, because all this feature really is is the definition of the separate fields for stage1 and stage2 granule support in ID_AA64MMFR0_EL1, and we already updated -cpu max to report its granule support that way when we were adding the LPA2 support. thanks -- PMM Peter Maydell (2): target/arm: Don't allow guest to use unimplemented granule sizes docs/system/arm/emulation.rst: Report FEAT_GTG support docs/system/arm/emulation.rst | 1 + target/arm/cpu.h | 33 ++++++++++ target/arm/helper.c | 110 +++++++++++++++++++++++++++++++--- 3 files changed, 136 insertions(+), 8 deletions(-) -- 2.25.1
