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Commit 82b05f08 authored by Marc Zyngier's avatar Marc Zyngier Committed by Greg Kroah-Hartman
Browse files

arm64: Move handling of erratum 1418040 into C code 



[ Upstream commit d49f7d7376d0c0daf8680984a37bd07581ac7d38 ]

Instead of dealing with erratum 1418040 on each entry and exit,
let's move the handling to __switch_to() instead, which has
several advantages:

- It can be applied when it matters (switching between 32 and 64
  bit tasks).
- It is written in C (yay!)
- It can rely on static keys rather than alternatives

Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Tested-by: default avatarSai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Reviewed-by: default avatarStephen Boyd <swboyd@chromium.org>
Acked-by: default avatarWill Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200731173824.107480-2-maz@kernel.org


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 7d44b707

arch/arm64/kernel/process.c

+34 −0
Original line number Diff line number Diff line
@@ -498,6 +498,39 @@ static void entry_task_switch(struct task_struct *next) 
	__this_cpu_write(__entry_task, next);

}



/*

 * ARM erratum 1418040 handling, affecting the 32bit view of CNTVCT.

 * Assuming the virtual counter is enabled at the beginning of times:

 *

 * - disable access when switching from a 64bit task to a 32bit task

 * - enable access when switching from a 32bit task to a 64bit task

 */

static void erratum_1418040_thread_switch(struct task_struct *prev,

					  struct task_struct *next)

{

	bool prev32, next32;

	u64 val;



	if (!(IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040) &&

	      cpus_have_const_cap(ARM64_WORKAROUND_1418040)))

		return;



	prev32 = is_compat_thread(task_thread_info(prev));

	next32 = is_compat_thread(task_thread_info(next));



	if (prev32 == next32)

		return;



	val = read_sysreg(cntkctl_el1);



	if (!next32)

		val |= ARCH_TIMER_USR_VCT_ACCESS_EN;

	else

		val &= ~ARCH_TIMER_USR_VCT_ACCESS_EN;



	write_sysreg(val, cntkctl_el1);

}



/*

 * Thread switching.

 */
@@ -514,6 +547,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, 
	uao_thread_switch(next);

	ptrauth_thread_switch(next);

	ssbs_thread_switch(next);

	erratum_1418040_thread_switch(prev, next);



	/*

	 * Complete any pending TLB or cache maintenance on this CPU in case