[PATCH 0/5] xtensa: enable context tracking and VIRT_CPU_ACCOUNTING_GEN

[PATCH 0/5] xtensa: enable context tracking and VIRT_CPU_ACCOUNTING_GEN

[Max Filippov]

Hello,

this series adds context tracking on xtensa and enables
HAVE_VIRT_CPU_ACCOUNTING_GEN allowing to build full tickless kernel.

Max Filippov (5):
  xtensa: drop dead code from entry.S
  xtensa: move trace_hardirqs_off call back to entry.S
  xtensa: use abi_* register names in the kernel exit code
  xtensa: enable context tracking
  xtensa: enable HAVE_VIRT_CPU_ACCOUNTING_GEN

 .../time/context-tracking/arch-support.txt    |   2 +-
 .../time/virt-cpuacct/arch-support.txt        |   2 +-
 arch/xtensa/Kconfig                           |   2 +
 arch/xtensa/kernel/entry.S                    | 120 +++++++++---------
 arch/xtensa/kernel/traps.c                    |  11 +-
 5 files changed, 66 insertions(+), 71 deletions(-)

-- 
2.30.2

[PATCH 1/5] xtensa: drop dead code from entry.S

[Max Filippov]

KERNEL_STACK_OVERFLOW_CHECK is incomplete and have never been enabled.
Remove it.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 arch/xtensa/kernel/entry.S | 18 ------------------
 1 file changed, 18 deletions(-)

diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 6b6eff658795..3c0b1aac7aba 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -28,15 +28,6 @@
 #include <asm/tlbflush.h>
 #include <variant/tie-asm.h>
 
-/* Unimplemented features. */
-
-#undef KERNEL_STACK_OVERFLOW_CHECK
-
-/* Not well tested.
- *
- * - fast_coprocessor
- */
-
 /*
  * Macro to find first bit set in WINDOWBASE from the left + 1
  *
@@ -350,15 +341,6 @@ KABI_W	_bbsi.l	a2, 3, 1f
 	l32i	a0, a1, PT_AREG0	# restore saved a0
 	wsr	a0, depc
 
-#ifdef KERNEL_STACK_OVERFLOW_CHECK
-
-	/*  Stack overflow check, for debugging  */
-	extui	a2, a1, TASK_SIZE_BITS,XX
-	movi	a3, SIZE??
-	_bge	a2, a3, out_of_stack_panic
-
-#endif
-
 /*
  * This is the common exception handler.
  * We get here from the user exception handler or simply by falling through
-- 
2.30.2

[PATCH 2/5] xtensa: move trace_hardirqs_off call back to entry.S

[Max Filippov]

Context tracking call must be done after hardirq tracking call,
otherwise lockdep_assert_irqs_disabled called from rcu_eqs_exit gives
a warning. To avoid context tracking logic duplication for IRQ/exception
entry paths move trace_hardirqs_off call back to common entry code.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 arch/xtensa/kernel/entry.S | 19 +++++++++++++------
 arch/xtensa/kernel/traps.c | 11 ++---------
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 3c0b1aac7aba..c85597a734aa 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -424,7 +424,6 @@ KABI_W	or	a3, a3, a0
 	moveqz	a3, a0, a2		# a3 = LOCKLEVEL iff interrupt
 KABI_W	movi	a2, PS_WOE_MASK
 KABI_W	or	a3, a3, a2
-	rsr	a2, exccause
 #endif
 
 	/* restore return address (or 0 if return to userspace) */
@@ -451,19 +450,27 @@ KABI_W	or	a3, a3, a2
 
 	save_xtregs_opt a1 a3 a4 a5 a6 a7 PT_XTREGS_OPT
 	
+#ifdef CONFIG_TRACE_IRQFLAGS
+	rsr		abi_tmp0, ps
+	extui		abi_tmp0, abi_tmp0, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
+	beqz		abi_tmp0, 1f
+	abi_call	trace_hardirqs_off
+1:
+#endif
+
 	/* Go to second-level dispatcher. Set up parameters to pass to the
 	 * exception handler and call the exception handler.
 	 */
 
-	rsr	a4, excsave1
-	addx4	a4, a2, a4
-	l32i	a4, a4, EXC_TABLE_DEFAULT		# load handler
-	mov	abi_arg1, a2			# pass EXCCAUSE
+	l32i	abi_arg1, a1, PT_EXCCAUSE	# pass EXCCAUSE
+	rsr	abi_tmp0, excsave1
+	addx4	abi_tmp0, abi_arg1, abi_tmp0
+	l32i	abi_tmp0, abi_tmp0, EXC_TABLE_DEFAULT	# load handler
 	mov	abi_arg0, a1			# pass stack frame
 
 	/* Call the second-level handler */
 
-	abi_callx	a4
+	abi_callx	abi_tmp0
 
 	/* Jump here for exception exit */
 	.global common_exception_return
diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index 82ced7b25b77..515719c7e750 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -242,12 +242,8 @@ DEFINE_PER_CPU(unsigned long, nmi_count);
 
 void do_nmi(struct pt_regs *regs)
 {
-	struct pt_regs *old_regs;
+	struct pt_regs *old_regs = set_irq_regs(regs);
 
-	if ((regs->ps & PS_INTLEVEL_MASK) < LOCKLEVEL)
-		trace_hardirqs_off();
-
-	old_regs = set_irq_regs(regs);
 	nmi_enter();
 	++*this_cpu_ptr(&nmi_count);
 	check_valid_nmi();
@@ -269,12 +265,9 @@ void do_interrupt(struct pt_regs *regs)
 		XCHAL_INTLEVEL6_MASK,
 		XCHAL_INTLEVEL7_MASK,
 	};
-	struct pt_regs *old_regs;
+	struct pt_regs *old_regs = set_irq_regs(regs);
 	unsigned unhandled = ~0u;
 
-	trace_hardirqs_off();
-
-	old_regs = set_irq_regs(regs);
 	irq_enter();
 
 	for (;;) {
-- 
2.30.2

[PATCH 3/5] xtensa: use abi_* register names in the kernel exit code

[Max Filippov]

Using plain register names is prone to errors when code is changed and
new calls are added between the register load and use. Change plain
register names to abi_* names in the call-heavy part of the kernel exit
code to clearly indicate what's supposed to be preserved and what's not.
Re-align code while at it.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 arch/xtensa/kernel/entry.S | 82 +++++++++++++++++++-------------------
 1 file changed, 42 insertions(+), 40 deletions(-)

diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index c85597a734aa..d09f2c38ba84 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -462,11 +462,11 @@ KABI_W	or	a3, a3, a2
 	 * exception handler and call the exception handler.
 	 */
 
-	l32i	abi_arg1, a1, PT_EXCCAUSE	# pass EXCCAUSE
-	rsr	abi_tmp0, excsave1
-	addx4	abi_tmp0, abi_arg1, abi_tmp0
-	l32i	abi_tmp0, abi_tmp0, EXC_TABLE_DEFAULT	# load handler
-	mov	abi_arg0, a1			# pass stack frame
+	l32i		abi_arg1, a1, PT_EXCCAUSE	# pass EXCCAUSE
+	rsr		abi_tmp0, excsave1
+	addx4		abi_tmp0, abi_arg1, abi_tmp0
+	l32i		abi_tmp0, abi_tmp0, EXC_TABLE_DEFAULT	# load handler
+	mov		abi_arg0, a1			# pass stack frame
 
 	/* Call the second-level handler */
 
@@ -477,23 +477,23 @@ KABI_W	or	a3, a3, a2
 common_exception_return:
 
 #if XTENSA_FAKE_NMI
-	l32i	abi_tmp0, a1, PT_EXCCAUSE
-	movi	abi_tmp1, EXCCAUSE_MAPPED_NMI
-	l32i	abi_saved1, a1, PT_PS
-	beq	abi_tmp0, abi_tmp1, .Lrestore_state
+	l32i		abi_tmp0, a1, PT_EXCCAUSE
+	movi		abi_tmp1, EXCCAUSE_MAPPED_NMI
+	l32i		abi_saved1, a1, PT_PS
+	beq		abi_tmp0, abi_tmp1, .Lrestore_state
 #endif
 .Ltif_loop:
-	irq_save a2, a3
+	irq_save	abi_tmp0, abi_tmp1
 #ifdef CONFIG_TRACE_IRQFLAGS
 	abi_call	trace_hardirqs_off
 #endif
 
 	/* Jump if we are returning from kernel exceptions. */
 
-	l32i	abi_saved1, a1, PT_PS
-	GET_THREAD_INFO(a2, a1)
-	l32i	a4, a2, TI_FLAGS
-	_bbci.l	abi_saved1, PS_UM_BIT, .Lexit_tif_loop_kernel
+	l32i		abi_saved1, a1, PT_PS
+	GET_THREAD_INFO(abi_tmp0, a1)
+	l32i		abi_saved0, abi_tmp0, TI_FLAGS
+	_bbci.l		abi_saved1, PS_UM_BIT, .Lexit_tif_loop_kernel
 
 	/* Specific to a user exception exit:
 	 * We need to check some flags for signal handling and rescheduling,
@@ -502,75 +502,77 @@ common_exception_return:
 	 * Note that we don't disable interrupts here. 
 	 */
 
-	_bbsi.l	a4, TIF_NEED_RESCHED, .Lresched
-	movi	a2, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL
-	bnone	a4, a2, .Lexit_tif_loop_user
+	_bbsi.l		abi_saved0, TIF_NEED_RESCHED, .Lresched
+	movi		abi_tmp0, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL
+	bnone		abi_saved0, abi_tmp0, .Lexit_tif_loop_user
 
-	l32i	a4, a1, PT_DEPC
-	bgeui	a4, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lrestore_state
+	l32i		abi_tmp0, a1, PT_DEPC
+	bgeui		abi_tmp0, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lrestore_state
 
 	/* Call do_signal() */
 
 #ifdef CONFIG_TRACE_IRQFLAGS
 	abi_call	trace_hardirqs_on
 #endif
-	rsil	a2, 0
-	mov	abi_arg0, a1
+	rsil		abi_tmp0, 0
+	mov		abi_arg0, a1
 	abi_call	do_notify_resume	# int do_notify_resume(struct pt_regs*)
-	j	.Ltif_loop
+	j		.Ltif_loop
 
 .Lresched:
 #ifdef CONFIG_TRACE_IRQFLAGS
 	abi_call	trace_hardirqs_on
 #endif
-	rsil	a2, 0
+	rsil		abi_tmp0, 0
 	abi_call	schedule	# void schedule (void)
-	j	.Ltif_loop
+	j		.Ltif_loop
 
 .Lexit_tif_loop_kernel:
 #ifdef CONFIG_PREEMPTION
-	_bbci.l	a4, TIF_NEED_RESCHED, .Lrestore_state
+	_bbci.l		abi_saved0, TIF_NEED_RESCHED, .Lrestore_state
 
 	/* Check current_thread_info->preempt_count */
 
-	l32i	a4, a2, TI_PRE_COUNT
-	bnez	a4, .Lrestore_state
+	l32i		abi_tmp1, abi_tmp0, TI_PRE_COUNT
+	bnez		abi_tmp1, .Lrestore_state
 	abi_call	preempt_schedule_irq
 #endif
-	j	.Lrestore_state
+	j		.Lrestore_state
 
 .Lexit_tif_loop_user:
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
-	_bbci.l	a4, TIF_DB_DISABLED, 1f
+	_bbci.l		abi_saved0, TIF_DB_DISABLED, 1f
 	abi_call	restore_dbreak
 1:
 #endif
 #ifdef CONFIG_DEBUG_TLB_SANITY
-	l32i	a4, a1, PT_DEPC
-	bgeui	a4, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lrestore_state
+	l32i		abi_tmp0, a1, PT_DEPC
+	bgeui		abi_tmp0, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lrestore_state
 	abi_call	check_tlb_sanity
 #endif
 
 .Lrestore_state:
 #ifdef CONFIG_TRACE_IRQFLAGS
-	extui	a4, abi_saved1, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
-	bgei	a4, LOCKLEVEL, 1f
+	extui		abi_tmp0, abi_saved1, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
+	bgei		abi_tmp0, LOCKLEVEL, 1f
 	abi_call	trace_hardirqs_on
 1:
 #endif
-	/* Restore optional registers. */
+	/*
+	 * Restore optional registers.
+	 * abi_arg* are used as temporary registers here.
+	 */
 
-	load_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT
+	load_xtregs_opt a1 abi_tmp0 abi_arg0 abi_arg1 abi_arg2 abi_arg3 PT_XTREGS_OPT
 
 	/* Restore SCOMPARE1 */
 
 #if XCHAL_HAVE_S32C1I
-	l32i    a2, a1, PT_SCOMPARE1
-	wsr     a2, scompare1
+	l32i		abi_tmp0, a1, PT_SCOMPARE1
+	wsr		abi_tmp0, scompare1
 #endif
-	wsr	abi_saved1, ps		/* disable interrupts */
-
-	_bbci.l	abi_saved1, PS_UM_BIT, kernel_exception_exit
+	wsr		abi_saved1, ps		/* disable interrupts */
+	_bbci.l		abi_saved1, PS_UM_BIT, kernel_exception_exit
 
 user_exception_exit:
 
-- 
2.30.2

[PATCH 4/5] xtensa: enable context tracking

[Max Filippov]

Put user exit context tracking call on the common kernel entry/exit path
(function calls are impossible at earlier kernel entry stages because
PS.EXCM is not cleared yet). Put user entry context tracking call on the
user exit path. Syscalls go through this common code too, so nothing
specific needs to be done for them.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 .../features/time/context-tracking/arch-support.txt      | 2 +-
 arch/xtensa/Kconfig                                      | 1 +
 arch/xtensa/kernel/entry.S                               | 9 +++++++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/features/time/context-tracking/arch-support.txt b/Documentation/features/time/context-tracking/arch-support.txt
index bb1c1801553e..72e7aadeda7e 100644
--- a/Documentation/features/time/context-tracking/arch-support.txt
+++ b/Documentation/features/time/context-tracking/arch-support.txt
@@ -27,5 +27,5 @@
     |       sparc: |  ok  |
     |          um: | TODO |
     |         x86: |  ok  |
-    |      xtensa: | TODO |
+    |      xtensa: |  ok  |
     -----------------------
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index e3ffd4564009..6134808a633d 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -31,6 +31,7 @@ config XTENSA
 	select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
+	select HAVE_CONTEXT_TRACKING
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_EXIT_THREAD
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index d09f2c38ba84..f2c789a5a92a 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -456,6 +456,12 @@ KABI_W	or	a3, a3, a2
 	beqz		abi_tmp0, 1f
 	abi_call	trace_hardirqs_off
 1:
+#endif
+#ifdef CONFIG_CONTEXT_TRACKING
+	l32i		abi_tmp0, a1, PT_PS
+	bbci.l		abi_tmp0, PS_UM_BIT, 1f
+	abi_call	context_tracking_user_exit
+1:
 #endif
 
 	/* Go to second-level dispatcher. Set up parameters to pass to the
@@ -540,6 +546,9 @@ common_exception_return:
 	j		.Lrestore_state
 
 .Lexit_tif_loop_user:
+#ifdef CONFIG_CONTEXT_TRACKING
+	abi_call	context_tracking_user_enter
+#endif
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
 	_bbci.l		abi_saved0, TIF_DB_DISABLED, 1f
 	abi_call	restore_dbreak
-- 
2.30.2

[PATCH 5/5] xtensa: enable HAVE_VIRT_CPU_ACCOUNTING_GEN

[Max Filippov]

There's no direct cputime_t manipulation in the xtensa arch code, so
generic virt CPU accounting may be enabled.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 Documentation/features/time/virt-cpuacct/arch-support.txt | 2 +-
 arch/xtensa/Kconfig                                       | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/features/time/virt-cpuacct/arch-support.txt b/Documentation/features/time/virt-cpuacct/arch-support.txt
index 5163a60a1c1e..c905aa3c1d81 100644
--- a/Documentation/features/time/virt-cpuacct/arch-support.txt
+++ b/Documentation/features/time/virt-cpuacct/arch-support.txt
@@ -27,5 +27,5 @@
     |       sparc: |  ok  |
     |          um: | TODO |
     |         x86: |  ok  |
-    |      xtensa: | TODO |
+    |      xtensa: |  ok  |
     -----------------------
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 6134808a633d..797355c142b3 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -43,6 +43,7 @@ config XTENSA
 	select HAVE_PERF_EVENTS
 	select HAVE_STACKPROTECTOR
 	select HAVE_SYSCALL_TRACEPOINTS
+	select HAVE_VIRT_CPU_ACCOUNTING_GEN
 	select IRQ_DOMAIN
 	select MODULES_USE_ELF_RELA
 	select PERF_USE_VMALLOC
-- 
2.30.2