From: Marc Zyngier <maz@kernel.org>
Date: Tue, 13 Apr 2021 14:46:58 +0000 (+0100)
Subject: Merge remote-tracking branch 'arm64/for-next/neon-softirqs-disabled' into kvmarm... 
X-Git-Tag: v5.13-rc1~76^2~38^2~4
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=3284cd638b85916ba6518f913586116412d190c6;p=linux-2.6-block.git

Merge remote-tracking branch 'arm64/for-next/neon-softirqs-disabled' into kvmarm-master/next

Signed-off-by: Marc Zyngier <maz@kernel.org>
---

3284cd638b85916ba6518f913586116412d190c6
diff --cc arch/arm64/include/asm/assembler.h
index 34ddd8a0f3dd,6ac38f7cf824..ad9ccc4f5a41
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@@ -15,7 -15,7 +15,8 @@@
  #include <asm-generic/export.h>
  
  #include <asm/asm-offsets.h>
+ #include <asm/alternative.h>
 +#include <asm/asm-bug.h>
  #include <asm/cpufeature.h>
  #include <asm/cputype.h>
  #include <asm/debug-monitors.h>
@@@ -705,95 -701,25 +714,33 @@@ USER(\label, ic	ivau, \tmp2)			// inval
  	isb
  .endm
  
 +.macro set_sctlr_el1, reg
 +	set_sctlr sctlr_el1, \reg
 +.endm
 +
 +.macro set_sctlr_el2, reg
 +	set_sctlr sctlr_el2, \reg
 +.endm
 +
- /*
-  * Check whether to yield to another runnable task from kernel mode NEON code
-  * (which runs with preemption disabled).
-  *
-  * if_will_cond_yield_neon
-  *        // pre-yield patchup code
-  * do_cond_yield_neon
-  *        // post-yield patchup code
-  * endif_yield_neon    <label>
-  *
-  * where <label> is optional, and marks the point where execution will resume
-  * after a yield has been performed. If omitted, execution resumes right after
-  * the endif_yield_neon invocation. Note that the entire sequence, including
-  * the provided patchup code, will be omitted from the image if
-  * CONFIG_PREEMPTION is not defined.
-  *
-  * As a convenience, in the case where no patchup code is required, the above
-  * sequence may be abbreviated to
-  *
-  * cond_yield_neon <label>
-  *
-  * Note that the patchup code does not support assembler directives that change
-  * the output section, any use of such directives is undefined.
-  *
-  * The yield itself consists of the following:
-  * - Check whether the preempt count is exactly 1 and a reschedule is also
-  *   needed. If so, calling of preempt_enable() in kernel_neon_end() will
-  *   trigger a reschedule. If it is not the case, yielding is pointless.
-  * - Disable and re-enable kernel mode NEON, and branch to the yield fixup
-  *   code.
-  *
-  * This macro sequence may clobber all CPU state that is not guaranteed by the
-  * AAPCS to be preserved across an ordinary function call.
-  */
- 
- 	.macro		cond_yield_neon, lbl
- 	if_will_cond_yield_neon
- 	do_cond_yield_neon
- 	endif_yield_neon	\lbl
- 	.endm
- 
- 	.macro		if_will_cond_yield_neon
- #ifdef CONFIG_PREEMPTION
- 	get_current_task	x0
- 	ldr		x0, [x0, #TSK_TI_PREEMPT]
- 	sub		x0, x0, #PREEMPT_DISABLE_OFFSET
- 	cbz		x0, .Lyield_\@
- 	/* fall through to endif_yield_neon */
- 	.subsection	1
- .Lyield_\@ :
- #else
- 	.section	".discard.cond_yield_neon", "ax"
- #endif
- 	.endm
- 
- 	.macro		do_cond_yield_neon
- 	bl		kernel_neon_end
- 	bl		kernel_neon_begin
- 	.endm
- 
- 	.macro		endif_yield_neon, lbl
- 	.ifnb		\lbl
- 	b		\lbl
- 	.else
- 	b		.Lyield_out_\@
- 	.endif
- 	.previous
- .Lyield_out_\@ :
- 	.endm
- 
  	/*
- 	 * Check whether preempt-disabled code should yield as soon as it
- 	 * is able. This is the case if re-enabling preemption a single
- 	 * time results in a preempt count of zero, and the TIF_NEED_RESCHED
- 	 * flag is set. (Note that the latter is stored negated in the
- 	 * top word of the thread_info::preempt_count field)
+ 	 * Check whether preempt/bh-disabled asm code should yield as soon as
+ 	 * it is able. This is the case if we are currently running in task
+ 	 * context, and either a softirq is pending, or the TIF_NEED_RESCHED
+ 	 * flag is set and re-enabling preemption a single time would result in
+ 	 * a preempt count of zero. (Note that the TIF_NEED_RESCHED flag is
+ 	 * stored negated in the top word of the thread_info::preempt_count
+ 	 * field)
  	 */
- 	.macro		cond_yield, lbl:req, tmp:req
- #ifdef CONFIG_PREEMPTION
+ 	.macro		cond_yield, lbl:req, tmp:req, tmp2:req
  	get_current_task \tmp
  	ldr		\tmp, [\tmp, #TSK_TI_PREEMPT]
+ 	/*
+ 	 * If we are serving a softirq, there is no point in yielding: the
+ 	 * softirq will not be preempted no matter what we do, so we should
+ 	 * run to completion as quickly as we can.
+ 	 */
+ 	tbnz		\tmp, #SOFTIRQ_SHIFT, .Lnoyield_\@
+ #ifdef CONFIG_PREEMPTION
  	sub		\tmp, \tmp, #PREEMPT_DISABLE_OFFSET
  	cbz		\tmp, \lbl
  #endif