Commit d49f7d73 authored by Marc Zyngier's avatar Marc Zyngier Committed by Catalin Marinas
Browse files

arm64: Move handling of erratum 1418040 into C code 



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>
parent 9123e3a7

arch/arm64/kernel/entry.S

+0 −21
Original line number Diff line number Diff line
@@ -170,19 +170,6 @@ alternative_cb_end 
	stp	x28, x29, [sp, #16 * 14]



	.if	\el == 0

	.if	\regsize == 32

	/*

	 * If we're returning from a 32-bit task on a system affected by

	 * 1418040 then re-enable userspace access to the virtual counter.

	 */

#ifdef CONFIG_ARM64_ERRATUM_1418040

alternative_if ARM64_WORKAROUND_1418040

	mrs	x0, cntkctl_el1

	orr	x0, x0, #2	// ARCH_TIMER_USR_VCT_ACCESS_EN

	msr	cntkctl_el1, x0

alternative_else_nop_endif

#endif

	.endif

	clear_gp_regs

	mrs	x21, sp_el0

	ldr_this_cpu	tsk, __entry_task, x20
@@ -294,14 +281,6 @@ alternative_else_nop_endif 
	tst	x22, #PSR_MODE32_BIT		// native task?

	b.eq	3f



#ifdef CONFIG_ARM64_ERRATUM_1418040

alternative_if ARM64_WORKAROUND_1418040

	mrs	x0, cntkctl_el1

	bic	x0, x0, #2			// ARCH_TIMER_USR_VCT_ACCESS_EN

	msr	cntkctl_el1, x0

alternative_else_nop_endif

#endif



#ifdef CONFIG_ARM64_ERRATUM_845719

alternative_if ARM64_WORKAROUND_845719

#ifdef CONFIG_PID_IN_CONTEXTIDR

arch/arm64/kernel/process.c

+34 −0
Original line number Diff line number Diff line
@@ -515,6 +515,39 @@ 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.

 */
@@ -530,6 +563,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, 
	entry_task_switch(next);

	uao_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

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