By default, highmem option is enabled for machine types later than virt-2.12. This allows qemu to place devices and RAM in physical address space above 32-bits. This can cause issues as according to the documentation Xen supports up to 12GiB of physical address space. Recently the issue was observed using runqemu, that was causing Linux running on top of Xen to stall when trying to access ECAM space placed by qemu at 256GiB mark. Even though this issue is most probably related to QEMU and not Xen (the investigation showed that it can map ECAM space correctly), it is best to avoid such issues by disabling highmem on qemuarm.
Signed-off-by: Michal Orzel <[email protected]> --- classes/qemuboot-xen-defaults.bbclass | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/classes/qemuboot-xen-defaults.bbclass b/classes/qemuboot-xen-defaults.bbclass index f1550cc..460cbe6 100644 --- a/classes/qemuboot-xen-defaults.bbclass +++ b/classes/qemuboot-xen-defaults.bbclass @@ -23,8 +23,10 @@ QB_DEFAULT_KERNEL:qemuarm = "xen-${MACHINE}" # 64-bit Arm: gic version 3 QB_MACHINE:qemuarm64 = "-machine virt,gic-version=3 -machine virtualization=true" -# 32-bit Arm -QB_MACHINE:qemuarm = "-machine virt -machine virtualization=true" +# 32-bit Arm: highmem=off +# Disable highmem so that qemu does not use highmem IO regions that end up +# being placed at the 256GiB mark (e.g. ECAM space) and can cause issues in Xen. +QB_MACHINE:qemuarm = "-machine virt,highmem=off -machine virtualization=true" # Increase the default qemu memory allocation to allow for the hypervisor. # Use a weak assignment to allow for change of default and override elsewhere. -- 2.25.1
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