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arm64: KVM: Expose sanitised cache type register to guest

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We currently permit CPUs in the same system to deviate in the exact
topology of the caches, and we subsequently hide this fact from user
space by exposing a sanitised value of the cache type register CTR_EL0.

However, guests running under KVM see the bare value of CTR_EL0, which
could potentially result in issues with, e.g., JITs or other pieces of
code that are sensitive to misreported cache line sizes.

So let's start trapping cache ID instructions if there is a mismatch,
and expose the sanitised version of CTR_EL0 to guests. Note that CTR_EL0
is treated as an invariant to KVM user space, so update that part as well.

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>
This commit is contained in:
Ard Biesheuvel
2019-01-31 14:17:17 +01:00
committed by Marc Zyngier
parent 64cf98fa55
commit f7f2b15c3d
3 changed files with 61 additions and 2 deletions
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arch/arm64/include/asm/sysreg.h
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@@ -361,6 +361,7 @@
#define SYS_CNTKCTL_EL1 sys_reg(3, 0, 14, 1, 0)
#define SYS_CCSIDR_EL1 sys_reg(3, 1, 0, 0, 0)
#define SYS_CLIDR_EL1 sys_reg(3, 1, 0, 0, 1)
#define SYS_AIDR_EL1 sys_reg(3, 1, 0, 0, 7)