linux-kernel - Re: [PATCH v5 4/8] powerpc/watchpoint: Move DAWR detection logic outside of hw

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Message-ID: <0a73280b-c231-a7bb-18d9-abf2a37ba24b@csgroup.eu>
Date:   Tue, 25 Aug 2020 11:30:15 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>, mpe@...erman.id.au,
        christophe.leroy@....fr
Cc:     mikey@...ling.org, paulus@...ba.org,
        naveen.n.rao@...ux.vnet.ibm.com, pedromfc@...ux.ibm.com,
        rogealve@...ux.ibm.com, jniethe5@...il.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 4/8] powerpc/watchpoint: Move DAWR detection logic
 outside of hw_breakpoint.c



Le 25/08/2020 à 06:36, Ravi Bangoria a écrit :
> Power10 hw has multiple DAWRs but hw doesn't tell which DAWR caused
> the exception. So we have a sw logic to detect that in hw_breakpoint.c.
> But hw_breakpoint.c gets compiled only with CONFIG_HAVE_HW_BREAKPOINT=Y.
> Move DAWR detection logic outside of hw_breakpoint.c so that it can be
> reused when CONFIG_HAVE_HW_BREAKPOINT is not set.
> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
> ---
>   arch/powerpc/include/asm/hw_breakpoint.h      |   8 +
>   arch/powerpc/kernel/Makefile                  |   3 +-
>   arch/powerpc/kernel/hw_breakpoint.c           | 159 +----------------
>   .../kernel/hw_breakpoint_constraints.c        | 162 ++++++++++++++++++
>   4 files changed, 174 insertions(+), 158 deletions(-)
>   create mode 100644 arch/powerpc/kernel/hw_breakpoint_constraints.c
> 

[...]

> diff --git a/arch/powerpc/kernel/hw_breakpoint_constraints.c b/arch/powerpc/kernel/hw_breakpoint_constraints.c
> new file mode 100644
> index 000000000000..867ee4aa026a
> --- /dev/null
> +++ b/arch/powerpc/kernel/hw_breakpoint_constraints.c
> @@ -0,0 +1,162 @@

[...]

> +
> +static int cache_op_size(void)
> +{
> +#ifdef __powerpc64__
> +	return ppc64_caches.l1d.block_size;
> +#else
> +	return L1_CACHE_BYTES;
> +#endif
> +}

You've got l1_dcache_bytes() in arch/powerpc/include/asm/cache.h to do that.

> +
> +void wp_get_instr_detail(struct pt_regs *regs, struct ppc_inst *instr,
> +			 int *type, int *size, unsigned long *ea)
> +{
> +	struct instruction_op op;
> +
> +	if (__get_user_instr_inatomic(*instr, (void __user *)regs->nip))
> +		return;
> +
> +	analyse_instr(&op, regs, *instr);
> +	*type = GETTYPE(op.type);
> +	*ea = op.ea;
> +#ifdef __powerpc64__
> +	if (!(regs->msr & MSR_64BIT))
> +		*ea &= 0xffffffffUL;
> +#endif

This #ifdef is unneeded, it should build fine on a 32 bits too.

> +
> +	*size = GETSIZE(op.type);
> +	if (*type == CACHEOP) {
> +		*size = cache_op_size();
> +		*ea &= ~(*size - 1);
> +	} else if (*type == LOAD_VMX || *type == STORE_VMX) {
> +		*ea &= ~(*size - 1);
> +	}
> +}
> 

Christophe