arm64: mm: fix booting with 52-bit address space
Joey reports that booting 52-bit VA capable builds on 52-bit VA capable CPUs is broken since commit 0d9b1ffe ("arm64: mm: make vabits_actual a build time constant if possible"). This is due to the fact that the primary CPU reads the vabits_actual variable before it has been assigned. The reason for deferring the assignment of vabits_actual was that we try to perform as few stores to memory as we can with the MMU and caches off, due to the cache coherency issues it creates. Since __cpu_setup() [which is where the read of vabits_actual occurs] is also called on the secondary boot path, we cannot just read the CPU ID registers directly, given that the size of the VA space is decided by the capabilities of the primary CPU. So let's read vabits_actual only on the secondary boot path, and read the CPU ID registers directly on the primary boot path, by making it a function parameter of __cpu_setup(). To ensure that all users of vabits_actual (including kasan_early_init()) observe the correct value, move the assignment of vabits_actual back into asm code, but still defer it to after the MMU and caches have been enabled. Cc: Will Deacon <will@kernel.org> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Fixes: 0d9b1ffe ("arm64: mm: make vabits_actual a build time constant if possible") Reported-by:Joey Gouly <joey.gouly@arm.com> Co-developed-by:
Joey Gouly <joey.gouly@arm.com> Signed-off-by:
Joey Gouly <joey.gouly@arm.com> Signed-off-by:
Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20220701111045.2944309-1-ardb@kernel.org Signed-off-by:
Will Deacon <will@kernel.org>
parent
bdbcd22d