[ANNOUNCE] v6.3.3-rt15
From: Sebastian Andrzej Siewior
Date: Fri May 19 2023 - 14:49:12 EST
Dear RT folks!
I'm pleased to announce the v6.3.3-rt15 patch set.
Changes since v6.3.3-rt14:
- Pavel Pisa reported a problem on Xilinx Zynq (ARM). While looking at
the backtrace, bad VFP handling was identified which was introduced
in v6.3 cycle. A few patches were backported and extended to
address the the VFP problem.
Known issues
None
The delta patch against v6.3.3-rt14 is appended below and can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.3/incr/patch-6.3.3-rt14-rt15.patch.xz
You can get this release via the git tree at:
git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v6.3.3-rt15
The RT patch against v6.3.3 can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.3/older/patch-6.3.3-rt15.patch.xz
The split quilt queue is available at:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.3/older/patches-6.3.3-rt15.tar.xz
Sebastian
diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 06b48ce23e1ca..505a306e0271a 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -244,19 +244,6 @@ THUMB( fpreg .req r7 )
.endm
#endif
- .macro local_bh_disable, ti, tmp
- ldr \tmp, [\ti, #TI_PREEMPT]
- add \tmp, \tmp, #SOFTIRQ_DISABLE_OFFSET
- str \tmp, [\ti, #TI_PREEMPT]
- .endm
-
- .macro local_bh_enable_ti, ti, tmp
- get_thread_info \ti
- ldr \tmp, [\ti, #TI_PREEMPT]
- sub \tmp, \tmp, #SOFTIRQ_DISABLE_OFFSET
- str \tmp, [\ti, #TI_PREEMPT]
- .endm
-
#define USERL(l, x...) \
9999: x; \
.pushsection __ex_table,"a"; \
diff --git a/arch/arm/vfp/entry.S b/arch/arm/vfp/entry.S
index 6dabb47617781..62206ef250371 100644
--- a/arch/arm/vfp/entry.S
+++ b/arch/arm/vfp/entry.S
@@ -23,15 +23,9 @@
@
ENTRY(do_vfp)
mov r1, r10
- mov r3, r9
- ldr r4, .LCvfp
- ldr pc, [r4] @ call VFP entry point
+ str lr, [sp, #-8]!
+ add r3, sp, #4
+ str r9, [r3]
+ bl vfp_entry
+ ldr pc, [sp], #8
ENDPROC(do_vfp)
-
-ENTRY(vfp_null_entry)
- ret lr
-ENDPROC(vfp_null_entry)
-
- .align 2
-.LCvfp:
- .word vfp_vector
diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index 60acd42e05786..860512042bc21 100644
--- a/arch/arm/vfp/vfphw.S
+++ b/arch/arm/vfp/vfphw.S
@@ -75,8 +75,6 @@
@ lr = unrecognised instruction return address
@ IRQs enabled.
ENTRY(vfp_support_entry)
- local_bh_disable r1, r4
-
ldr r11, [r1, #TI_CPU] @ CPU number
add r10, r1, #TI_VFPSTATE @ r10 = workspace
@@ -174,14 +172,15 @@ ENTRY(vfp_support_entry)
@ out before setting an FPEXC that
@ stops us reading stuff
VFPFMXR FPEXC, r1 @ Restore FPEXC last
+ mov sp, r3 @ we think we have handled things
+ pop {lr}
sub r2, r2, #4 @ Retry current instruction - if Thumb
str r2, [sp, #S_PC] @ mode it's two 16-bit instructions,
@ else it's one 32-bit instruction, so
@ always subtract 4 from the following
@ instruction address.
- local_bh_enable_ti r10, r4
- ret r3 @ we think we have handled things
+ b vfp_exit @ tail call
look_for_VFP_exceptions:
@ Check for synchronous or asynchronous exception
@@ -204,13 +203,13 @@ ENTRY(vfp_support_entry)
@ not recognised by VFP
DBGSTR "not VFP"
- local_bh_enable_ti r10, r4
- ret lr
+ b vfp_exit @ tail call
process_exception:
DBGSTR "bounce"
+ mov sp, r3 @ setup for a return to the user code.
+ pop {lr}
mov r2, sp @ nothing stacked - regdump is at TOS
- mov lr, r3 @ setup for a return to the user code.
@ Now call the C code to package up the bounce to the support code
@ r0 holds the trigger instruction
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 01bc48d738478..a2745d17e9c71 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -32,10 +32,9 @@
/*
* Our undef handlers (in entry.S)
*/
-asmlinkage void vfp_support_entry(void);
-asmlinkage void vfp_null_entry(void);
+asmlinkage void vfp_support_entry(u32, void *, u32, u32);
-asmlinkage void (*vfp_vector)(void) = vfp_null_entry;
+static bool have_vfp __ro_after_init;
/*
* Dual-use variable.
@@ -55,6 +54,34 @@ static unsigned int __initdata VFP_arch;
*/
union vfp_state *vfp_current_hw_state[NR_CPUS];
+/*
+ * Claim ownership of the VFP unit.
+ *
+ * The caller may change VFP registers until vfp_unlock() is called.
+ *
+ * local_bh_disable() is used to disable preemption and to disable VFP
+ * processing in softirq context. On PREEMPT_RT kernels local_bh_disable() is
+ * not sufficient because it only serializes soft interrupt related sections
+ * via a local lock, but stays preemptible. Disabling preemption is the right
+ * choice here as bottom half processing is always in thread context on RT
+ * kernels so it implicitly prevents bottom half processing as well.
+ */
+static void vfp_lock(void)
+{
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+ local_bh_disable();
+ else
+ preempt_disable();
+}
+
+static void vfp_unlock(void)
+{
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+ local_bh_enable();
+ else
+ preempt_enable();
+}
+
/*
* Is 'thread's most up to date state stored in this CPUs hardware?
* Must be called from non-preemptible context.
@@ -240,7 +267,7 @@ static void vfp_panic(char *reason, u32 inst)
/*
* Process bitmask of exception conditions.
*/
-static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_regs *regs)
+static int vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr)
{
int si_code = 0;
@@ -248,8 +275,7 @@ static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_
if (exceptions == VFP_EXCEPTION_ERROR) {
vfp_panic("unhandled bounce", inst);
- vfp_raise_sigfpe(FPE_FLTINV, regs);
- return;
+ return FPE_FLTINV;
}
/*
@@ -277,8 +303,7 @@ static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_
RAISE(FPSCR_OFC, FPSCR_OFE, FPE_FLTOVF);
RAISE(FPSCR_IOC, FPSCR_IOE, FPE_FLTINV);
- if (si_code)
- vfp_raise_sigfpe(si_code, regs);
+ return si_code;
}
/*
@@ -323,6 +348,8 @@ static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs)
void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
{
u32 fpscr, orig_fpscr, fpsid, exceptions;
+ int si_code2 = 0;
+ int si_code = 0;
pr_debug("VFP: bounce: trigger %08x fpexc %08x\n", trigger, fpexc);
@@ -370,7 +397,7 @@ void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
* unallocated VFP instruction but with FPSCR.IXE set and not
* on VFP subarch 1.
*/
- vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr, regs);
+ si_code = vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr);
goto exit;
}
@@ -395,7 +422,7 @@ void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
*/
exceptions = vfp_emulate_instruction(trigger, fpscr, regs);
if (exceptions)
- vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
+ si_code2 = vfp_raise_exceptions(exceptions, trigger, orig_fpscr);
/*
* If there isn't a second FP instruction, exit now. Note that
@@ -414,9 +441,14 @@ void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
emulate:
exceptions = vfp_emulate_instruction(trigger, orig_fpscr, regs);
if (exceptions)
- vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
+ si_code = vfp_raise_exceptions(exceptions, trigger, orig_fpscr);
+
exit:
- local_bh_enable();
+ vfp_unlock();
+ if (si_code2)
+ vfp_raise_sigfpe(si_code2, regs);
+ if (si_code)
+ vfp_raise_sigfpe(si_code, regs);
}
static void vfp_enable(void *unused)
@@ -515,11 +547,9 @@ static inline void vfp_pm_init(void) { }
*/
void vfp_sync_hwstate(struct thread_info *thread)
{
- unsigned int cpu = get_cpu();
+ vfp_lock();
- local_bh_disable();
-
- if (vfp_state_in_hw(cpu, thread)) {
+ if (vfp_state_in_hw(raw_smp_processor_id(), thread)) {
u32 fpexc = fmrx(FPEXC);
/*
@@ -530,8 +560,7 @@ void vfp_sync_hwstate(struct thread_info *thread)
fmxr(FPEXC, fpexc);
}
- local_bh_enable();
- put_cpu();
+ vfp_unlock();
}
/* Ensure that the thread reloads the hardware VFP state on the next use. */
@@ -645,6 +674,30 @@ static int vfp_starting_cpu(unsigned int unused)
return 0;
}
+/*
+ * Entered with:
+ *
+ * r0 = instruction opcode (32-bit ARM or two 16-bit Thumb)
+ * r1 = thread_info pointer
+ * r2 = PC value to resume execution after successful emulation
+ * r3 = normal "successful" return address
+ * lr = unrecognised instruction return address
+ */
+asmlinkage void vfp_entry(u32 trigger, struct thread_info *ti, u32 resume_pc,
+ u32 resume_return_address)
+{
+ if (unlikely(!have_vfp))
+ return;
+
+ vfp_lock();
+ vfp_support_entry(trigger, ti, resume_pc, resume_return_address);
+}
+
+asmlinkage void vfp_exit(void)
+{
+ vfp_unlock();
+}
+
#ifdef CONFIG_KERNEL_MODE_NEON
static int vfp_kmode_exception(struct pt_regs *regs, unsigned int instr)
@@ -720,7 +773,7 @@ void kernel_neon_begin(void)
unsigned int cpu;
u32 fpexc;
- local_bh_disable();
+ vfp_lock();
/*
* Kernel mode NEON is only allowed outside of hardirq context with
@@ -751,7 +804,7 @@ void kernel_neon_end(void)
{
/* Disable the NEON/VFP unit. */
fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
- local_bh_enable();
+ vfp_unlock();
}
EXPORT_SYMBOL(kernel_neon_end);
@@ -798,7 +851,6 @@ static int __init vfp_init(void)
vfpsid = fmrx(FPSID);
barrier();
unregister_undef_hook(&vfp_detect_hook);
- vfp_vector = vfp_null_entry;
pr_info("VFP support v0.3: ");
if (VFP_arch) {
@@ -883,7 +935,7 @@ static int __init vfp_init(void)
"arm/vfp:starting", vfp_starting_cpu,
vfp_dying_cpu);
- vfp_vector = vfp_support_entry;
+ have_vfp = true;
thread_register_notifier(&vfp_notifier_block);
vfp_pm_init();
diff --git a/localversion-rt b/localversion-rt
index 08b3e75841adc..18777ec0c27d4 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt14
+-rt15