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Date: Tue, 10 Aug 2021 16:33:08 +0800
From: Xiongwei Song <sxwjean@...il.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Xiongwei Song <sxwjean@...com>,
PowerPC <linuxppc-dev@...ts.ozlabs.org>, oleg@...hat.com,
Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>, npiggin@...il.com,
ravi.bangoria@...ux.ibm.com, aneesh.kumar@...ux.ibm.com,
efremov@...ux.com,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] powerpc: Optimize register usage for esr register
On Sat, Aug 7, 2021 at 2:57 PM Christophe Leroy
<christophe.leroy@...roup.eu> wrote:
>
>
>
> Le 07/08/2021 à 03:02, sxwjean@...com a écrit :
> > From: Xiongwei Song <sxwjean@...il.com>
> >
> > Create an anonymous union for dsisr and esr regsiters, we can reference
> > esr to get the exception detail when CONFIG_4xx=y or CONFIG_BOOKE=y.
> > Otherwise, reference dsisr. This makes code more clear.
> >
> > Signed-off-by: Xiongwei Song <sxwjean@...il.com>
> > ---
> > arch/powerpc/include/asm/ptrace.h | 5 ++++-
> > arch/powerpc/kernel/process.c | 2 +-
> > arch/powerpc/kernel/ptrace/ptrace.c | 2 ++
> > arch/powerpc/kernel/traps.c | 2 +-
> > arch/powerpc/platforms/44x/machine_check.c | 4 ++--
> > arch/powerpc/platforms/4xx/machine_check.c | 2 +-
> > 6 files changed, 11 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
> > index 3e5d470a6155..c252d04b1206 100644
> > --- a/arch/powerpc/include/asm/ptrace.h
> > +++ b/arch/powerpc/include/asm/ptrace.h
> > @@ -44,7 +44,10 @@ struct pt_regs
> > #endif
> > unsigned long trap;
> > unsigned long dar;
> > - unsigned long dsisr;
> > + union {
> > + unsigned long dsisr;
> > + unsigned long esr;
> > + };
> > unsigned long result;
> > };
> > };
> > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> > index 185beb290580..f74af8f9133c 100644
> > --- a/arch/powerpc/kernel/process.c
> > +++ b/arch/powerpc/kernel/process.c
> > @@ -1499,7 +1499,7 @@ static void __show_regs(struct pt_regs *regs)
> > trap == INTERRUPT_DATA_STORAGE ||
> > trap == INTERRUPT_ALIGNMENT) {
> > if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE))
> > - pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->dsisr);
> > + pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->esr);
> > else
> > pr_cont("DAR: "REG" DSISR: %08lx ", regs->dar, regs->dsisr);
> > }
> > diff --git a/arch/powerpc/kernel/ptrace/ptrace.c b/arch/powerpc/kernel/ptrace/ptrace.c
> > index 0a0a33eb0d28..a222fd4d6334 100644
> > --- a/arch/powerpc/kernel/ptrace/ptrace.c
> > +++ b/arch/powerpc/kernel/ptrace/ptrace.c
> > @@ -375,6 +375,8 @@ void __init pt_regs_check(void)
> > offsetof(struct user_pt_regs, dar));
> > BUILD_BUG_ON(offsetof(struct pt_regs, dsisr) !=
> > offsetof(struct user_pt_regs, dsisr));
> > + BUILD_BUG_ON(offsetof(struct pt_regs, esr) !=
> > + offsetof(struct user_pt_regs, dsisr));
>
> esr and dsisr are the same, so checking the same thing a second time is pointless.
Hmm...it's better to check if the changes on pt_regs structure is
expected I think.
Regards,
Xiongwei
>
> > BUILD_BUG_ON(offsetof(struct pt_regs, result) !=
> > offsetof(struct user_pt_regs, result));
> >
> > diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> > index dfbce527c98e..2164f5705a0b 100644
> > --- a/arch/powerpc/kernel/traps.c
> > +++ b/arch/powerpc/kernel/traps.c
> > @@ -562,7 +562,7 @@ static inline int check_io_access(struct pt_regs *regs)
> > #ifdef CONFIG_PPC_ADV_DEBUG_REGS
> > /* On 4xx, the reason for the machine check or program exception
> > is in the ESR. */
> > -#define get_reason(regs) ((regs)->dsisr)
> > +#define get_reason(regs) ((regs)->esr)
> > #define REASON_FP ESR_FP
> > #define REASON_ILLEGAL (ESR_PIL | ESR_PUO)
> > #define REASON_PRIVILEGED ESR_PPR
> > diff --git a/arch/powerpc/platforms/44x/machine_check.c b/arch/powerpc/platforms/44x/machine_check.c
> > index a5c898bb9bab..5d19daacd78a 100644
> > --- a/arch/powerpc/platforms/44x/machine_check.c
> > +++ b/arch/powerpc/platforms/44x/machine_check.c
> > @@ -11,7 +11,7 @@
> >
> > int machine_check_440A(struct pt_regs *regs)
> > {
> > - unsigned long reason = regs->dsisr;
> > + unsigned long reason = regs->esr;
> >
> > printk("Machine check in kernel mode.\n");
> > if (reason & ESR_IMCP){
> > @@ -48,7 +48,7 @@ int machine_check_440A(struct pt_regs *regs)
> > #ifdef CONFIG_PPC_47x
> > int machine_check_47x(struct pt_regs *regs)
> > {
> > - unsigned long reason = regs->dsisr;
> > + unsigned long reason = regs->esr;
> > u32 mcsr;
> >
> > printk(KERN_ERR "Machine check in kernel mode.\n");
> > diff --git a/arch/powerpc/platforms/4xx/machine_check.c b/arch/powerpc/platforms/4xx/machine_check.c
> > index a71c29892a91..a905da1d6f41 100644
> > --- a/arch/powerpc/platforms/4xx/machine_check.c
> > +++ b/arch/powerpc/platforms/4xx/machine_check.c
> > @@ -10,7 +10,7 @@
> >
> > int machine_check_4xx(struct pt_regs *regs)
> > {
> > - unsigned long reason = regs->dsisr;
> > + unsigned long reason = regs->esr;
> >
> > if (reason & ESR_IMCP) {
> > printk("Instruction");
> >
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