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ANDROID: Fix compat hwcap reporting on asymmetric 32-bit SoCs

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When support for asymmetric 32-bit SoCs is enabled on the kernel
command-line, system_supports_32bit_el0() will always return true since
a late-onlined CPU could introduce the need for 32-bit support.

In order to avoid checking for the presence of compat hwcaps on
64-bit-only CPUs, adjust the verification of compat hwcaps for
late-onlined CPUs so that it is only performed for CPUs which actually
have 32-bit support. This allows late CPU hotplug of 64-bit-only CPUs on
a mismatched system. When mismatched support is not enabled,
incompatible CPUs are preventing from coming online by the CPU
capability.

Bug: 186482502
Change-Id: I22c285a54dbf9abb1a35e2bb608e5a41517f0ad0
Signed-off-by: Will Deacon <willdeacon@google.com>
This commit is contained in:
Will Deacon 2021-05-17 11:48:05 +01:00 • committed by Quentin Perret
commit 73599c263e
1 changed files with 10 additions and 6 deletions
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16
arch/arm64/kernel/cpufeature.c
View file

@ -2685,7 +2685,7 @@ static void check_early_cpu_features(void)
}
static void
verify_local_elf_hwcaps(const struct arm64_cpu_capabilities *caps)
__verify_local_elf_hwcaps(const struct arm64_cpu_capabilities *caps)
{
for (; caps->matches; caps++)
@ -2696,6 +2696,14 @@ verify_local_elf_hwcaps(const struct arm64_cpu_capabilities *caps)
}
}
static void verify_local_elf_hwcaps(void)
{
__verify_local_elf_hwcaps(arm64_elf_hwcaps);
if (id_aa64pfr0_32bit_el0(read_cpuid(ID_AA64PFR0_EL1)))
__verify_local_elf_hwcaps(compat_elf_hwcaps);
}
static void verify_sve_features(void)
{
u64 safe_zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1);
@ -2760,11 +2768,7 @@ static void verify_local_cpu_capabilities(void)
* on all secondary CPUs.
*/
verify_local_cpu_caps(SCOPE_ALL & ~SCOPE_BOOT_CPU);
verify_local_elf_hwcaps(arm64_elf_hwcaps);
if (system_supports_32bit_el0())
verify_local_elf_hwcaps(compat_elf_hwcaps);
verify_local_elf_hwcaps();
if (system_supports_sve())
verify_sve_features();