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arm64: ssbd: Add support for PSTATE.SSBS rather than trapping to EL3

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On CPUs with support for PSTATE.SSBS, the kernel can toggle the SSBD
state without needing to call into firmware.

This patch hooks into the existing SSBD infrastructure so that SSBS is
used on CPUs that support it, but it's all made horribly complicated by
the very real possibility of big/little systems that don't uniformly
provide the new capability.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Will Deacon
2018-08-07 13:47:06 +01:00
committed by Catalin Marinas
parent 0bf0f444b2
commit 8f04e8e6e2
8 changed files with 106 additions and 2 deletions
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4
arch/arm64/kernel/process.c
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@@ -358,6 +358,10 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
if (IS_ENABLED(CONFIG_ARM64_UAO) &&
cpus_have_const_cap(ARM64_HAS_UAO))
childregs->pstate |= PSR_UAO_BIT;
if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE)
childregs->pstate |= PSR_SSBS_BIT;
p->thread.cpu_context.x19 = stack_start;
p->thread.cpu_context.x20 = stk_sz;
}