[PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
From: Christophe Leroy
call_do_irq() and call_do_softirq() are simple enough to be
worth inlining.
Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It
also allows GCC to keep the saved ksp_limit in an nonvolatile reg.
This is inspired from S390 arch. Several other arches do more or
less the same. The way sparc arch does seems odd thought.
Signed-off-by: Christophe Leroy
Signed-off-by: Michael Ellerman
---
v2: no change.
v3: no change.
v4:
- comment reminding the purpose of the inline asm block.
- added r2 as clobbered reg
v5:
- Limiting the change to PPC32 for now.
- removed r2 from the clobbered regs list (on PPC32 r2 points to current all
the time)
- Removed patch 1 and merged ksp_limit handling in here.
v6:
- Rebase on top of merge-test (ca6e327fefb2).
- Remove the ksp_limit stuff as it's doesn't exist anymore.
v7:
mpe:
- Enable for 64-bit too. This all in-kernel code calling in-kernel
code, and must use the kernel TOC.
- Use named parameters for the inline asm.
- Reformat inline asm.
- Mark as always_inline.
- Drop unused ret from call_do_softirq(), add r3 as clobbered.
---
arch/powerpc/include/asm/irq.h | 2 --
arch/powerpc/kernel/irq.c | 41 ++
arch/powerpc/kernel/misc_32.S | 25 -
arch/powerpc/kernel/misc_64.S | 22 --
4 files changed, 41 insertions(+), 49 deletions(-)
diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index f3f264e441a7..b2bd58830430 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -53,8 +53,6 @@ extern void *mcheckirq_ctx[NR_CPUS];
extern void *hardirq_ctx[NR_CPUS];
extern void *softirq_ctx[NR_CPUS];
-void call_do_softirq(void *sp);
-void call_do_irq(struct pt_regs *regs, void *sp);
extern void do_IRQ(struct pt_regs *regs);
extern void __init init_IRQ(void);
extern void __do_irq(struct pt_regs *regs);
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 5b72abbff96c..260effc0a435 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -667,6 +667,47 @@ static inline void check_stack_overflow(void)
}
}
+static __always_inline void call_do_softirq(const void *sp)
+{
+ /* Temporarily switch r1 to sp, call __do_softirq() then restore r1. */
+ asm volatile (
+PPC_STLU " %%r1, %[offset](%[sp]) ;"
+ "mr %%r1, %[sp] ;"
+ "bl %[callee] ;"
+PPC_LL " %%r1, 0(%%r1) ;"
+: // Outputs
+: // Inputs
+ [sp] "b" (sp), [offset] "i" (THREAD_SIZE -
STACK_FRAME_OVERHEAD),
+ [callee] "i" (__do_softirq)
+: // Clobbers
+ "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
+ "cr7", "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
+ "r11", "r12"
+ );
+}
+
+static __always_inline void call_do_irq(struct pt_regs *regs, void *sp)
+{
+ register unsigned long r3 asm("r3") = (unsigned long)regs;
+
+ /* Temporarily switch r1 to sp, call __do_irq() then restore r1. */
+ asm volatile (
+PPC_STLU " %%r1, %[offset](%[sp]) ;"
+ "mr %%r1, %[sp] ;"
+ "bl %[callee] ;"
+PPC_LL " %%r1, 0(%%r1) ;"
+: // Outputs
+ "+r" (r3)
+: // Inputs
+ [sp] "b" (sp), [offset] "i" (THREAD_SIZE -
STACK_FRAME_OVERHEAD),
+ [callee] "i" (__do_irq)
+: // Clobbers
+ "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
+ "cr7", "r0", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
+ "r11", "r12"
+ );
+}
+
void __do_irq(struct pt_regs *regs)
{
unsigned int irq;
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index acc410043b96..6a076bef2932 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -27,31 +27,6 @@
.text
-_GLOBAL(call_do_softirq)
- mflrr0
- stw r0,4(r1)
- stwur1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)
- mr r1,r3
- bl __do_softirq
- lwz r1,0(r1)
- lwz r0,4(r1)
- mtlrr0
- blr
-
-/*
- * void call_do_irq(struct pt_regs *regs, void *sp);
- */
-_GLOBAL(call_do_irq)
- mflrr0
- stw r0,4(r1)
- stwur1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r4)
- mr r1,r4
- bl __do_irq
- lwz r1,0(r1)
- lwz r0,4(r1)
- mtlrr0
- blr
-
/*
* This returns the high 64 bits of the product of two 64-bit numbers.
*/
diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index 070465825c21..4b761a18a74
Re: [PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
Le 20/03/2021 à 13:22, Michael Ellerman a écrit :
From: Christophe Leroy
call_do_irq() and call_do_softirq() are simple enough to be
worth inlining.
Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It
also allows GCC to keep the saved ksp_limit in an nonvolatile reg.
We don't have the ksp_limit anymore, I forgot to remove the above text.
This is inspired from S390 arch. Several other arches do more or
less the same. The way sparc arch does seems odd thought.
Signed-off-by: Christophe Leroy
Signed-off-by: Michael Ellerman
---
v2: no change.
v3: no change.
v4:
- comment reminding the purpose of the inline asm block.
- added r2 as clobbered reg
v5:
- Limiting the change to PPC32 for now.
- removed r2 from the clobbered regs list (on PPC32 r2 points to current all
the time)
- Removed patch 1 and merged ksp_limit handling in here.
v6:
- Rebase on top of merge-test (ca6e327fefb2).
- Remove the ksp_limit stuff as it's doesn't exist anymore.
v7:
mpe:
- Enable for 64-bit too. This all in-kernel code calling in-kernel
code, and must use the kernel TOC.
Great.
- Use named parameters for the inline asm.
Hmm. It is the first time we use named parameters in powerpc assembly, isn't it
?
I saw when investigating userspace access that x86 is using named parameters
widely.
Wondering, how would the below look like with named parameters (from
__put_user_asm2_goto) ?
stw%X1 %L0, %L1
- Reformat inline asm.
- Mark as always_inline.
- Drop unused ret from call_do_softirq(), add r3 as clobbered.
---
arch/powerpc/include/asm/irq.h | 2 --
arch/powerpc/kernel/irq.c | 41 ++
arch/powerpc/kernel/misc_32.S | 25 -
arch/powerpc/kernel/misc_64.S | 22 --
4 files changed, 41 insertions(+), 49 deletions(-)
diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index f3f264e441a7..b2bd58830430 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -53,8 +53,6 @@ extern void *mcheckirq_ctx[NR_CPUS];
extern void *hardirq_ctx[NR_CPUS];
extern void *softirq_ctx[NR_CPUS];
-void call_do_softirq(void *sp);
-void call_do_irq(struct pt_regs *regs, void *sp);
extern void do_IRQ(struct pt_regs *regs);
extern void __init init_IRQ(void);
extern void __do_irq(struct pt_regs *regs);
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 5b72abbff96c..260effc0a435 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -667,6 +667,47 @@ static inline void check_stack_overflow(void)
}
}
+static __always_inline void call_do_softirq(const void *sp)
+{
+ /* Temporarily switch r1 to sp, call __do_softirq() then restore r1. */
+ asm volatile (
+PPC_STLU "%%r1, %[offset](%[sp]) ;"
+ "mr%%r1, %[sp] ;"
+ "bl%[callee] ;"
+PPC_LL " %%r1, 0(%%r1) ;"
+: // Outputs
+: // Inputs
+ [sp] "b" (sp), [offset] "i" (THREAD_SIZE -
STACK_FRAME_OVERHEAD),
+ [callee] "i" (__do_softirq)
+: // Clobbers
+ "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
+ "cr7", "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
+ "r11", "r12"
+ );
+}
+
+static __always_inline void call_do_irq(struct pt_regs *regs, void *sp)
+{
+ register unsigned long r3 asm("r3") = (unsigned long)regs;
+
+ /* Temporarily switch r1 to sp, call __do_irq() then restore r1. */
+ asm volatile (
+PPC_STLU "%%r1, %[offset](%[sp]) ;"
+ "mr%%r1, %[sp] ;"
+ "bl%[callee] ;"
+PPC_LL " %%r1, 0(%%r1) ;"
+: // Outputs
+ "+r" (r3)
+: // Inputs
+ [sp] "b" (sp), [offset] "i" (THREAD_SIZE -
STACK_FRAME_OVERHEAD),
+ [callee] "i" (__do_irq)
+: // Clobbers
+ "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
+ "cr7", "r0", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
+ "r11", "r12"
+ );
+}
+
void __do_irq(struct pt_regs *regs)
{
unsigned int irq;
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index acc410043b96..6a076bef2932 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -27,31 +27,6 @@
.text
-_GLOBAL(call_do_softirq)
- mflrr0
- stw r0,4(r1)
- stwur1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)
- mr r1,r3
- bl __do_softirq
- lwz r1,0(r1)
- lwz r0,4(r1)
- mtlrr0
- blr
-
-/*
- * void call_do_irq(struct pt_regs *re
Re: [PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
Christophe Leroy writes: > Le 20/03/2021 à 13:22, Michael Ellerman a écrit : >> From: Christophe Leroy >> >> call_do_irq() and call_do_softirq() are simple enough to be >> worth inlining. >> >> Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It >> also allows GCC to keep the saved ksp_limit in an nonvolatile reg. > > We don't have the ksp_limit anymore, I forgot to remove the above text. No worries, I'll edit it when I apply it. >> This is inspired from S390 arch. Several other arches do more or >> less the same. The way sparc arch does seems odd thought. >> >> Signed-off-by: Christophe Leroy >> Signed-off-by: Michael Ellerman >> --- >> >> v2: no change. >> v3: no change. >> v4: >> - comment reminding the purpose of the inline asm block. >> - added r2 as clobbered reg >> v5: >> - Limiting the change to PPC32 for now. >> - removed r2 from the clobbered regs list (on PPC32 r2 points to current all >> the time) >> - Removed patch 1 and merged ksp_limit handling in here. >> v6: >> - Rebase on top of merge-test (ca6e327fefb2). >> - Remove the ksp_limit stuff as it's doesn't exist anymore. >> >> v7: >> mpe: >> - Enable for 64-bit too. This all in-kernel code calling in-kernel >>code, and must use the kernel TOC. > > Great. > >> - Use named parameters for the inline asm. > > Hmm. It is the first time we use named parameters in powerpc assembly, isn't > it ? Not quite the first. See load_unaligned_zeropad(). And also my soon to be merged code in: http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20210211135130.3474832-5-...@ellerman.id.au/ > I saw when investigating userspace access that x86 is using named parameters > widely. Yeah I'd like us to use it more, I think it helps readability a lot. > Wondering, how would the below look like with named parameters (from > __put_user_asm2_goto) ? > > stw%X1 %L0, %L1 Not sure, possibly that's too complicated for it :) cheers
Re: [PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
On Wed, Mar 24, 2021 at 11:26:01PM +1100, Michael Ellerman wrote:
> Christophe Leroy writes:
> > Hmm. It is the first time we use named parameters in powerpc assembly,
> > isn't it ?
> Yeah I'd like us to use it more, I think it helps readability a lot.
..in some cases. Not in most cases :-(
> > Wondering, how would the below look like with named parameters (from
> > __put_user_asm2_goto) ?
> >
> > stw%X1 %L0, %L1
>
> Not sure, possibly that's too complicated for it :)
asm("stw%X[name1] %L[name0],%L[name1]" :: [name0]"r"(x), [name1]"m"(p));
Yes, it is not more readable *at all*.
Segher
Re: [PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
On Sat, 20 Mar 2021 23:22:27 +1100, Michael Ellerman wrote: > call_do_irq() and call_do_softirq() are simple enough to be > worth inlining. > > Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It > also allows GCC to keep the saved ksp_limit in an nonvolatile reg. > > This is inspired from S390 arch. Several other arches do more or > less the same. The way sparc arch does seems odd thought. Applied to powerpc/next. [1/1] powerpc/irq: Inline call_do_irq() and call_do_softirq() https://git.kernel.org/powerpc/c/48cf12d88969bd4238b8769767eb476970319d93 cheers
Re: [PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
On Sat, Mar 20, 2021 at 11:22:27PM +1100, Michael Ellerman wrote:
> From: Christophe Leroy
>
> call_do_irq() and call_do_softirq() are simple enough to be
> worth inlining.
>
> Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It
> also allows GCC to keep the saved ksp_limit in an nonvolatile reg.
>
> This is inspired from S390 arch. Several other arches do more or
> less the same. The way sparc arch does seems odd thought.
>
> Signed-off-by: Christophe Leroy
> Signed-off-by: Michael Ellerman
> ---
>
> v2: no change.
> v3: no change.
> v4:
> - comment reminding the purpose of the inline asm block.
> - added r2 as clobbered reg
> v5:
> - Limiting the change to PPC32 for now.
> - removed r2 from the clobbered regs list (on PPC32 r2 points to current all
> the time)
> - Removed patch 1 and merged ksp_limit handling in here.
> v6:
> - Rebase on top of merge-test (ca6e327fefb2).
> - Remove the ksp_limit stuff as it's doesn't exist anymore.
>
> v7:
> mpe:
> - Enable for 64-bit too. This all in-kernel code calling in-kernel
> code, and must use the kernel TOC.
> - Use named parameters for the inline asm.
> - Reformat inline asm.
> - Mark as always_inline.
> - Drop unused ret from call_do_softirq(), add r3 as clobbered.
> ---
> arch/powerpc/include/asm/irq.h | 2 --
> arch/powerpc/kernel/irq.c | 41 ++
> arch/powerpc/kernel/misc_32.S | 25 -
> arch/powerpc/kernel/misc_64.S | 22 --
> 4 files changed, 41 insertions(+), 49 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
> index f3f264e441a7..b2bd58830430 100644
> --- a/arch/powerpc/include/asm/irq.h
> +++ b/arch/powerpc/include/asm/irq.h
> @@ -53,8 +53,6 @@ extern void *mcheckirq_ctx[NR_CPUS];
> extern void *hardirq_ctx[NR_CPUS];
> extern void *softirq_ctx[NR_CPUS];
>
> -void call_do_softirq(void *sp);
> -void call_do_irq(struct pt_regs *regs, void *sp);
> extern void do_IRQ(struct pt_regs *regs);
> extern void __init init_IRQ(void);
> extern void __do_irq(struct pt_regs *regs);
> diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
> index 5b72abbff96c..260effc0a435 100644
> --- a/arch/powerpc/kernel/irq.c
> +++ b/arch/powerpc/kernel/irq.c
> @@ -667,6 +667,47 @@ static inline void check_stack_overflow(void)
> }
> }
>
> +static __always_inline void call_do_softirq(const void *sp)
> +{
> + /* Temporarily switch r1 to sp, call __do_softirq() then restore r1. */
> + asm volatile (
> + PPC_STLU " %%r1, %[offset](%[sp]) ;"
> + "mr %%r1, %[sp] ;"
> + "bl %[callee] ;"
> + PPC_LL " %%r1, 0(%%r1) ;"
> + : // Outputs
> + : // Inputs
> +[sp] "b" (sp), [offset] "i" (THREAD_SIZE -
> STACK_FRAME_OVERHEAD),
> +[callee] "i" (__do_softirq)
> + : // Clobbers
> +"lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
> +"cr7", "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
> +"r11", "r12"
> + );
> +}
> +
> +static __always_inline void call_do_irq(struct pt_regs *regs, void *sp)
> +{
> + register unsigned long r3 asm("r3") = (unsigned long)regs;
> +
> + /* Temporarily switch r1 to sp, call __do_irq() then restore r1. */
> + asm volatile (
> + PPC_STLU " %%r1, %[offset](%[sp]) ;"
> + "mr %%r1, %[sp] ;"
> + "bl %[callee] ;"
> + PPC_LL " %%r1, 0(%%r1) ;"
> + : // Outputs
> +"+r" (r3)
> + : // Inputs
> +[sp] "b" (sp), [offset] "i" (THREAD_SIZE -
> STACK_FRAME_OVERHEAD),
> +[callee] "i" (__do_irq)
> + : // Clobbers
> +"lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
> +"cr7", "r0", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
> +"r11", "r12"
> + );
> +}
> +
> void __do_irq(struct pt_regs *regs)
> {
> unsigned int irq;
> diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
> index acc410043b96..6a076bef2932 100644
> --- a/arch/powerpc/kernel/misc_32.S
> +++ b/arch/powerpc/kernel/misc_32.S
> @@ -27,31 +27,6 @@
>
> .text
>
> -_GLOBAL(call_do_softirq)
> - mflrr0
> - stw r0,4(r1)
> - stwur1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)
> - mr r1,r3
> - bl __do_softirq
> - lwz r1,0(r1)
> - lwz r0,4(r1)
> - mtlrr0
> - blr
> -
> -/*
> - * void call_do_irq(struct pt_regs *regs, void *sp);
> - */
> -_GLOBAL(call_do_irq)
> - mflrr0
> - stw r0,4(r1)
> - stwur1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r4)
> - mr r1,r4
> - bl __do_irq
> - lwz r1,0(r1)
Re: [PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
Le 26/04/2021 à 20:50, Nathan Chancellor a écrit :
On Sat, Mar 20, 2021 at 11:22:27PM +1100, Michael Ellerman wrote:
From: Christophe Leroy
call_do_irq() and call_do_softirq() are simple enough to be
worth inlining.
Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It
also allows GCC to keep the saved ksp_limit in an nonvolatile reg.
This is inspired from S390 arch. Several other arches do more or
less the same. The way sparc arch does seems odd thought.
Signed-off-by: Christophe Leroy
Signed-off-by: Michael Ellerman
This change caused our ppc44x_defconfig builds to hang when powering
down in QEMU:
https://github.com/ClangBuiltLinux/continuous-integration2/runs/2304364629?check_suite_focus=true#logs
This is probably something with clang given that GCC 10.3.0 works fine
but due to the nature of the change, I have no idea how to tell what is
going wrong. I tried to do some rudimentary debugging with gdb but that
did not really get me anywhere.
The kernel was built with just 'CC=clang' and it is reproducible with
all versions of clang that the kernel supports.
The QEMU invocation is visible at the link above, it is done with our
boot-qemu.sh in this repo, which also houses the rootfs:
https://github.com/ClangBuiltLinux/boot-utils
Happy to provide any other information or debug/test as directed!
With GCC:
03f0 :
3f0: 94 21 ff f0 stwur1,-16(r1)
3f4: 7c 08 02 a6 mflrr0
3f8: 3d 20 00 00 lis r9,0
3fa: R_PPC_ADDR16_HA.data..read_mostly+0x4
3fc: 93 e1 00 0c stw r31,12(r1)
400: 90 01 00 14 stw r0,20(r1)
404: 83 e9 00 00 lwz r31,0(r9)
406: R_PPC_ADDR16_LO.data..read_mostly+0x4
408: 94 3f 1f f0 stwur1,8176(r31)
40c: 7f e1 fb 78 mr r1,r31
410: 48 00 00 01 bl 410
410: R_PPC_REL24__do_softirq
414: 80 21 00 00 lwz r1,0(r1)
418: 80 01 00 14 lwz r0,20(r1)
41c: 83 e1 00 0c lwz r31,12(r1)
420: 38 21 00 10 addir1,r1,16
424: 7c 08 03 a6 mtlrr0
428: 4e 80 00 20 blr
With CLANG:
03e8 :
3e8: 94 21 ff f0 stwur1,-16(r1)
3ec: 93 c1 00 08 stw r30,8(r1)
3f0: 3c 60 00 00 lis r3,0
3f2: R_PPC_ADDR16_HAsoftirq_ctx
3f4: 83 c3 00 00 lwz r30,0(r3)
3f6: R_PPC_ADDR16_LOsoftirq_ctx
3f8: 94 3e 1f f0 stwur1,8176(r30)
3fc: 7f c1 f3 78 mr r1,r30
400: 48 00 00 01 bl 400
400: R_PPC_REL24__do_softirq
404: 80 21 00 00 lwz r1,0(r1)
408: 83 c1 00 08 lwz r30,8(r1)
40c: 38 21 00 10 addir1,r1,16
410: 4e 80 00 20 blr
As you can see, CLANG doesn't save/restore 'lr' allthought 'lr' is explicitely listed in the
registers clobbered by the inline assembly:
>> +static __always_inline void call_do_softirq(const void *sp)
>> +{
>> + /* Temporarily switch r1 to sp, call __do_softirq() then restore r1.
*/
>> + asm volatile (
>> + PPC_STLU "%%r1, %[offset](%[sp]) ;"
>> + "mr%%r1, %[sp] ;"
>> + "bl%[callee] ;"
>> + PPC_LL " %%r1, 0(%%r1) ;"
>> + : // Outputs
>> + : // Inputs
>> + [sp] "b" (sp), [offset] "i" (THREAD_SIZE -
STACK_FRAME_OVERHEAD),
>> + [callee] "i" (__do_softirq)
>> + : // Clobbers
>> + "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
>> + "cr7", "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9",
"r10",
>> + "r11", "r12"
>> + );
Re: [PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
On Mon, Apr 26, 2021 at 11:39 PM Christophe Leroy
wrote:
>
>
>
> Le 26/04/2021 à 20:50, Nathan Chancellor a écrit :
> > On Sat, Mar 20, 2021 at 11:22:27PM +1100, Michael Ellerman wrote:
> >> From: Christophe Leroy
> >>
> >> call_do_irq() and call_do_softirq() are simple enough to be
> >> worth inlining.
> >>
> >> Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It
> >> also allows GCC to keep the saved ksp_limit in an nonvolatile reg.
> >>
> >> This is inspired from S390 arch. Several other arches do more or
> >> less the same. The way sparc arch does seems odd thought.
> >>
> >> Signed-off-by: Christophe Leroy
> >> Signed-off-by: Michael Ellerman
> >>
> >
> > This change caused our ppc44x_defconfig builds to hang when powering
> > down in QEMU:
> >
> > https://github.com/ClangBuiltLinux/continuous-integration2/runs/2304364629?check_suite_focus=true#logs
> >
> > This is probably something with clang given that GCC 10.3.0 works fine
> > but due to the nature of the change, I have no idea how to tell what is
> > going wrong. I tried to do some rudimentary debugging with gdb but that
> > did not really get me anywhere.
> >
> > The kernel was built with just 'CC=clang' and it is reproducible with
> > all versions of clang that the kernel supports.
> >
> > The QEMU invocation is visible at the link above, it is done with our
> > boot-qemu.sh in this repo, which also houses the rootfs:
> >
> > https://github.com/ClangBuiltLinux/boot-utils
> >
> > Happy to provide any other information or debug/test as directed!
> >
>
> With GCC:
>
> 03f0 :
> 3f0: 94 21 ff f0 stwur1,-16(r1)
> 3f4: 7c 08 02 a6 mflrr0
> 3f8: 3d 20 00 00 lis r9,0
> 3fa: R_PPC_ADDR16_HA.data..read_mostly+0x4
> 3fc: 93 e1 00 0c stw r31,12(r1)
> 400: 90 01 00 14 stw r0,20(r1)
> 404: 83 e9 00 00 lwz r31,0(r9)
> 406: R_PPC_ADDR16_LO.data..read_mostly+0x4
> 408: 94 3f 1f f0 stwur1,8176(r31)
> 40c: 7f e1 fb 78 mr r1,r31
> 410: 48 00 00 01 bl 410
> 410: R_PPC_REL24__do_softirq
> 414: 80 21 00 00 lwz r1,0(r1)
> 418: 80 01 00 14 lwz r0,20(r1)
> 41c: 83 e1 00 0c lwz r31,12(r1)
> 420: 38 21 00 10 addir1,r1,16
> 424: 7c 08 03 a6 mtlrr0
> 428: 4e 80 00 20 blr
>
>
> With CLANG:
>
> 03e8 :
> 3e8: 94 21 ff f0 stwur1,-16(r1)
> 3ec: 93 c1 00 08 stw r30,8(r1)
> 3f0: 3c 60 00 00 lis r3,0
> 3f2: R_PPC_ADDR16_HAsoftirq_ctx
> 3f4: 83 c3 00 00 lwz r30,0(r3)
> 3f6: R_PPC_ADDR16_LOsoftirq_ctx
> 3f8: 94 3e 1f f0 stwur1,8176(r30)
> 3fc: 7f c1 f3 78 mr r1,r30
> 400: 48 00 00 01 bl 400
> 400: R_PPC_REL24__do_softirq
> 404: 80 21 00 00 lwz r1,0(r1)
> 408: 83 c1 00 08 lwz r30,8(r1)
> 40c: 38 21 00 10 addir1,r1,16
> 410: 4e 80 00 20 blr
>
>
> As you can see, CLANG doesn't save/restore 'lr' allthought 'lr' is
> explicitely listed in the
> registers clobbered by the inline assembly:
Ah, thanks for debugging this. Will follow up in
https://bugs.llvm.org/show_bug.cgi?id=50147.
>
> >> +static __always_inline void call_do_softirq(const void *sp)
> >> +{
> >> + /* Temporarily switch r1 to sp, call __do_softirq() then restore r1.
> */
> >> + asm volatile (
> >> +PPC_STLU " %%r1, %[offset](%[sp]) ;"
> >> + "mr %%r1, %[sp] ;"
> >> + "bl %[callee] ;"
> >> +PPC_LL " %%r1, 0(%%r1) ;"
> >> +: // Outputs
> >> +: // Inputs
> >> + [sp] "b" (sp), [offset] "i" (THREAD_SIZE -
> STACK_FRAME_OVERHEAD),
> >> + [callee] "i" (__do_softirq)
> >> +: // Clobbers
> >> + "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
> >> + "cr7", "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9",
> "r10",
> >> + "r11", "r12"
> >> + );
>
> --
> You received this message because you are subscribed to the Google Groups
> "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to clang-built-linux+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/clang-built-linux/de6fc09f-97f5-c934-6393-998ec766b48a%40csgroup.eu.
--
Thanks,
~Nick Desaulniers
Re: [PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
On Tue, Apr 27, 2021 at 1:42 PM Nick Desaulniers wrote: > > On Mon, Apr 26, 2021 at 11:39 PM Christophe Leroy > wrote: > > > > As you can see, CLANG doesn't save/restore 'lr' allthought 'lr' is > > explicitely listed in the > > registers clobbered by the inline assembly: > > Ah, thanks for debugging this. Will follow up in > https://bugs.llvm.org/show_bug.cgi?id=50147. Looks like there's a fix posted for LLVM in: https://reviews.llvm.org/D101657 Though trying to test it in QEMU, I'm hitting some assertion failure booting a kernel (even without that patch to LLVM): qemu-system-ppc: ../../hw/pci/pci.c:253: pci_bus_change_irq_level: Assertion `irq_num >= 0' failed. That's with QEMU emulator version 5.2.0 (Debian 1:5.2+dfsg-9) I didn't see anything in https://bugs.launchpad.net/qemu/ about it, but figured I'd share in case that assertion failure looked familiar to anyone. -- Thanks, ~Nick Desaulniers
Re: [PATCH v7] powerpc/irq: Inline call_do_irq() and call_do_softirq()
On Fri, Apr 30, 2021 at 2:33 PM Nick Desaulniers wrote: > > On Tue, Apr 27, 2021 at 1:42 PM Nick Desaulniers > wrote: > > > > On Mon, Apr 26, 2021 at 11:39 PM Christophe Leroy > > wrote: > > > > > > As you can see, CLANG doesn't save/restore 'lr' allthought 'lr' is > > > explicitely listed in the > > > registers clobbered by the inline assembly: > > > > Ah, thanks for debugging this. Will follow up in > > https://bugs.llvm.org/show_bug.cgi?id=50147. > > Looks like there's a fix posted for LLVM in: https://reviews.llvm.org/D101657 > > Though trying to test it in QEMU, I'm hitting some assertion failure > booting a kernel (even without that patch to LLVM): > qemu-system-ppc: ../../hw/pci/pci.c:253: pci_bus_change_irq_level: > Assertion `irq_num >= 0' failed. > That's with > QEMU emulator version 5.2.0 (Debian 1:5.2+dfsg-9) > > I didn't see anything in https://bugs.launchpad.net/qemu/ about it, > but figured I'd share in case that assertion failure looked familiar > to anyone. Nathan pointed out some previous reports; looks like others are hitting this, too: https://github.com/ClangBuiltLinux/linux/issues/1345#issuecomment-830451276 -- Thanks, ~Nick Desaulniers
