Improve the 'highmem' option docs to note that by default we assume that a 32-bit kernel on an LPAE-capable CPU has LPAE enabled, and what the consequences are.
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> Reviewed-by: Alex Bennée <alex.ben...@linaro.org> Reviewed-by: Eric Auger <eric.au...@redhat.com> Message-id: 20240109170834.1387457-1-peter.mayd...@linaro.org --- docs/system/arm/virt.rst | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst index 7c4c80180c6..c245c52b7ac 100644 --- a/docs/system/arm/virt.rst +++ b/docs/system/arm/virt.rst @@ -96,7 +96,13 @@ mte highmem Set ``on``/``off`` to enable/disable placing devices and RAM in physical address space above 32 bits. The default is ``on`` for machine types - later than ``virt-2.12``. + later than ``virt-2.12`` when the CPU supports an address space + bigger than 32 bits (i.e. 64-bit CPUs, and 32-bit CPUs with the + Large Physical Address Extension (LPAE) feature). If you want to + boot a 32-bit kernel which does not have ``CONFIG_LPAE`` enabled on + a CPU type which implements LPAE, you will need to manually set + this to ``off``; otherwise some devices, such as the PCI controller, + will not be accessible. compact-highmem Set ``on``/``off`` to enable/disable the compact layout for high memory regions. -- 2.34.1
