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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: Marc Zyngier <maz@kernel.org>
Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200731173824.107480-2-maz@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Marc Zyngier 2020-07-31 18:38:23 +01:00 committed by Catalin Marinas
parent 9123e3a74e
commit d49f7d7376
2 changed files with 34 additions and 21 deletions
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21
arch/arm64/kernel/entry.S
View File

@ -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

34
arch/arm64/kernel/process.c
View File

@ -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