From f0098155d337cab638cf18e37a3e9257d653d481 Mon Sep 17 00:00:00 2001
From: Hector Martin <marcan@marcan.st>
Date: Mon, 15 Mar 2021 11:56:28 +0000
Subject: arm64: Always keep DAIF.[IF] in sync

Apple SoCs (A11 and newer) have some interrupt sources hardwired to the
FIQ line. We implement support for this by simply treating IRQs and FIQs
the same way in the interrupt vectors.

To support these systems, the FIQ mask bit needs to be kept in sync with
the IRQ mask bit, so both kinds of exceptions are masked together. No
other platforms should be delivering FIQ exceptions right now, and we
already unmask FIQ in normal process context, so this should not have an
effect on other systems - if spurious FIQs were arriving, they would
already panic the kernel.

Signed-off-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Hector Martin <marcan@marcan.st>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210315115629.57191-6-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/assembler.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'arch/arm64/include/asm/assembler.h')

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index ca31594d3d6c..b76a71e84b7c 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -40,9 +40,9 @@
 	msr	daif, \flags
 	.endm
 
-	/* IRQ is the lowest priority flag, unconditionally unmask the rest. */
-	.macro enable_da_f
-	msr	daifclr, #(8 | 4 | 1)
+	/* IRQ/FIQ are the lowest priority flags, unconditionally unmask the rest. */
+	.macro enable_da
+	msr	daifclr, #(8 | 4)
 	.endm
 
 /*
@@ -50,7 +50,7 @@
  */
 	.macro	save_and_disable_irq, flags
 	mrs	\flags, daif
-	msr	daifset, #2
+	msr	daifset, #3
 	.endm
 
 	.macro	restore_irq, flags
-- 
cgit 


From 27248fe1abb2a0e6fe4c744c25700f557b04466c Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Tue, 2 Mar 2021 10:01:10 +0100
Subject: arm64: assembler: remove conditional NEON yield macros

The users of the conditional NEON yield macros have all been switched to
the simplified cond_yield macro, and so the NEON specific ones can be
removed.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210302090118.30666-2-ardb@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/assembler.h | 70 --------------------------------------
 1 file changed, 70 deletions(-)

(limited to 'arch/arm64/include/asm/assembler.h')

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index ca31594d3d6c..e0fc1d424f9b 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -692,76 +692,6 @@ USER(\label, ic	ivau, \tmp2)			// invalidate I line PoU
 	isb
 .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
-- 
cgit 


From 4c4dcd3541f83d216f2e403cb83dd431e09759b1 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Tue, 2 Mar 2021 10:01:11 +0100
Subject: arm64: assembler: introduce wxN aliases for wN registers

The AArch64 asm syntax has this slightly tedious property that the names
used in mnemonics to refer to registers depend on whether the opcode in
question targets the entire 64-bits (xN), or only the least significant
8, 16 or 32 bits (wN). When writing parameterized code such as macros,
this can be annoying, as macro arguments don't lend themselves to
indexed lookups, and so generating a reference to wN in a macro that
receives xN as an argument is problematic.

For instance, an upcoming patch that modifies the implementation of the
cond_yield macro to be able to refer to 32-bit registers would need to
modify invocations such as

  cond_yield	3f, x8

to

  cond_yield	3f, 8

so that the second argument can be token pasted after x or w to emit the
correct register reference. Unfortunately, this interferes with the self
documenting nature of the first example, where the second argument is
obviously a register, whereas in the second example, one would need to
go and look at the code to find out what '8' means.

So let's fix this by defining wxN aliases for all xN registers, which
resolve to the 32-bit alias of each respective 64-bit register. This
allows the macro implementation to paste the xN reference after a w to
obtain the correct register name.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210302090118.30666-3-ardb@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/assembler.h | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'arch/arm64/include/asm/assembler.h')

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index e0fc1d424f9b..7b076ccd1a54 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -23,6 +23,14 @@
 #include <asm/ptrace.h>
 #include <asm/thread_info.h>
 
+	/*
+	 * Provide a wxN alias for each wN register so what we can paste a xN
+	 * reference after a 'w' to obtain the 32-bit version.
+	 */
+	.irp	n,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30
+	wx\n	.req	w\n
+	.endr
+
 	.macro save_and_disable_daif, flags
 	mrs	\flags, daif
 	msr	daifset, #0xf
-- 
cgit 


From 13150149aa6ded1e6bbe0025beac6e12604dd87c Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Tue, 2 Mar 2021 10:01:12 +0100
Subject: arm64: fpsimd: run kernel mode NEON with softirqs disabled

Kernel mode NEON can be used in task or softirq context, but only in
a non-nesting manner, i.e., softirq context is only permitted if the
interrupt was not taken at a point where the kernel was using the NEON
in task context.

This means all users of kernel mode NEON have to be aware of this
limitation, and either need to provide scalar fallbacks that may be much
slower (up to 20x for AES instructions) and potentially less safe, or
use an asynchronous interface that defers processing to a later time
when the NEON is guaranteed to be available.

Given that grabbing and releasing the NEON is cheap, we can relax this
restriction, by increasing the granularity of kernel mode NEON code, and
always disabling softirq processing while the NEON is being used in task
context.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210302090118.30666-4-ardb@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/assembler.h | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

(limited to 'arch/arm64/include/asm/assembler.h')

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 7b076ccd1a54..6ac38f7cf824 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -15,6 +15,7 @@
 #include <asm-generic/export.h>
 
 #include <asm/asm-offsets.h>
+#include <asm/alternative.h>
 #include <asm/cpufeature.h>
 #include <asm/cputype.h>
 #include <asm/debug-monitors.h>
@@ -701,19 +702,32 @@ USER(\label, ic	ivau, \tmp2)			// invalidate I line PoU
 .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
+	adr_l		\tmp, irq_stat + IRQ_CPUSTAT_SOFTIRQ_PENDING
+	this_cpu_offset	\tmp2
+	ldr		w\tmp, [\tmp, \tmp2]
+	cbnz		w\tmp, \lbl	// yield on pending softirq in task context
+.Lnoyield_\@:
 	.endm
 
 /*
-- 
cgit