linux-kernel - Re: [PATCH 4/8] riscv: Introduce support for hardware break/watchpoints

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Message-ID: <20250822174715.1269138-5-jesse@rivosinc.com>
Date: Tue,  2 Sep 2025 13:13:12 +0800
From: Qingfang Deng <dqfext@...il.com>
To: Jesse Taube <jesse@...osinc.com>,
	linux-riscv@...ts.infradead.org,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alex@...ti.fr>,
	Oleg Nesterov <oleg@...hat.com>,
	Kees Cook <kees@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang Kan" <kan.liang@...ux.intel.com>,
	Shuah Khan <shuah@...nel.org>,
	Himanshu Chauhan <hchauhan@...tanamicro.com>,
	Charlie Jenkins <charlie@...osinc.com>,
	Samuel Holland <samuel.holland@...ive.com>,
	Conor Dooley <conor.dooley@...rochip.com>,
	Deepak Gupta <debug@...osinc.com>,
	Andrew Jones <ajones@...tanamicro.com>,
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	Anup Patel <apatel@...tanamicro.com>,
	Mayuresh Chitale <mchitale@...tanamicro.com>,
	Evan Green <evan@...osinc.com>,
	WangYuli <wangyuli@...ontech.com>,
	Huacai Chen <chenhuacai@...nel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Luis Chamberlain <mcgrof@...nel.org>,
	"Mike Rapoport (Microsoft)" <rppt@...nel.org>,
	Nam Cao <namcao@...utronix.de>,
	Yunhui Cui <cuiyunhui@...edance.com>,
	Joel Granados <joel.granados@...nel.org>,
	Clément Léger <cleger@...osinc.com>,
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	Nylon Chen <nylon.chen@...ive.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	Joey Gouly <joey.gouly@....com>,
	Ravi Bangoria <ravi.bangoria@....com>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-perf-users@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	Joel Stanley <joel@....id.au>
Subject: Re: [PATCH 4/8] riscv: Introduce support for hardware break/watchpoints

Hi Jesse and Charlie,

On Fri, 22 Aug 2025 10:47:11 -0700, Jesse Taube <jesse@...osinc.com> wrote:
> +static int arch_smp_setup_sbi_shmem(unsigned int cpu)
> +{
> +	union sbi_dbtr_shmem_entry *dbtr_shmem;
> +	unsigned long shmem_pa;
> +	struct sbiret ret;
> +	int rc;
> +
> +	dbtr_shmem = per_cpu_ptr(&sbi_dbtr_shmem, cpu);
> +	if (!dbtr_shmem) {
> +		pr_err("Invalid per-cpu shared memory for debug triggers\n");
> +		return -ENODEV;
> +	}
> +
> +	shmem_pa = virt_to_phys(dbtr_shmem);
> +
> +	ret = sbi_ecall(SBI_EXT_DBTR, SBI_EXT_DBTR_SETUP_SHMEM,
> +			SBI_SHMEM_LO(shmem_pa), SBI_SHMEM_HI(shmem_pa), 0, 0, 0, 0);
> +	if (ret.error) {
> +		pr_warn("%s: failed to setup shared memory. error: %ld\n", __func__, ret.error);
> +		return sbi_err_map_linux_errno(ret.error);
> +	}
> +
> +	pr_debug("CPU %d: HW Breakpoint shared memory registered.\n", cpu);
> +
> +	return rc;

rc is uninitialized.
You may remove the variable and just return 0 here.

> +}

Regards,
Qingfang