arm64: KVM: Describe data or unified caches as having 1 set and 1 way

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On SMP ARM systems, cache maintenance by set/way should only ever be
done in the context of onlining or offlining CPUs, which is typically
done by bare metal firmware and never in a virtual machine. For this
reason, we trap set/way cache maintenance operations and replace them
with conditional flushing of the entire guest address space.

Due to this trapping, the set/way arguments passed into the set/way
ops are completely ignored, and thus irrelevant. This also means that
the set/way geometry is equally irrelevant, and we can simply report
it as 1 set and 1 way, so that legacy 32-bit ARM system software (i.e.,
the kind that only receives odd fixes) doesn't take a performance hit
due to the trapping when iterating over the cachelines.

Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

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Ard Biesheuvel 2019-01-31 14:17:18 +01:00 • committed by Marc Zyngier

parent f7f2b15c3d

commit 793acf870e

2 changed files with 17 additions and 1 deletions

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arch/arm64/include/asm/kvm_emulate.h

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15

arch/arm64/kvm/sys_regs.c

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