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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2dd89ebc548sm9967905ad.37.2026.09.16.04.24.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Sep 2026 04:24:11 -0700 (PDT) Message-ID: Date: Wed, 16 Sep 2026 21:24:05 +1000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm_mpam: resctrl: Catch and propagate error from get_cpu_cacheinfo_id() To: Ben Horgan , Andre Przywara , James Morse Cc: Reinette Chatre , Fenghua Yu , Tony Luck , Dave Martin , Yin Li , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260902143757.3469690-1-andre.przywara@arm.com> <2c682691-3037-4d62-a941-bc41baca35aa@arm.com> From: Gavin Shan In-Reply-To: <2c682691-3037-4d62-a941-bc41baca35aa@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: IA9vLnk3edHsmnadzYlMMDqjBsgp6TZqGbtzu5S-8qk_1789557853 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260916_042418_197937_D36F32FE X-CRM114-Status: GOOD ( 23.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 9/16/26 7:49 PM, Ben Horgan wrote: > Hi Andre, > > On 07/09/2026 13:59, Ben Horgan wrote: >> Hi Andre, >> >> On 02/09/2026 15:37, Andre Przywara wrote: >>> get_cpu_cacheinfo_id() can fail, in which case it returns a negative >>> error value. >>> >>> Check the returned value for this error condition, before passing the >>> value on to other code, which would hide the negative number in some high >>> value in the unsigned type. >>> >>> Fixes: 36528c7681b8 ("arm_mpam: resctrl: Add support for 'MB' resource") >>> Signed-off-by: Andre Przywara >> >> This looks good to me. Out of interest what led you to find this? >> >> Reviewed-by: Ben Horgan > > I seem to have been a bit hasty here. > > Sashiko points out at [1] that 0xFFFFFFFF is the only value we were previously considering invalid > and that the value coming from dt or acpi can provid other valid values that would after this patch > be considered invalid. > > [1] https://sashiko.dev/#/patchset/20260902143757.3469690-1-andre.przywara%40arm.com > I think Sashiko is correct that the check 'if (cache_id < 0) return -ENOENT' is incorrect because only -1 is a invalid ID. The correct check would be: u32 cache_id = get_cpu_cacheinfo_id(cpu, 3); if (cache_id = UINT_MAX) return -ENOENT; Or int cache_id = get_cpu_cacheinfo_id(cpu, 3); if (cache_id == -1) return -ENOENT; Thanks, Gavin > Thanks, > > Ben> >> Thanks, >> >> Ben >> >>> --- >>> drivers/resctrl/mpam_resctrl.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c >>> index 9d223057953ab..a5e661eff86d7 100644 >>> --- a/drivers/resctrl/mpam_resctrl.c >>> +++ b/drivers/resctrl/mpam_resctrl.c >>> @@ -786,7 +786,10 @@ static u32 get_mba_min(struct mpam_props *cprops) >>> /* Find the L3 cache that has affinity with this CPU */ >>> static int find_l3_equivalent_bitmask(int cpu, cpumask_var_t tmp_cpumask) >>> { >>> - u32 cache_id = get_cpu_cacheinfo_id(cpu, 3); >>> + int cache_id = get_cpu_cacheinfo_id(cpu, 3); >>> + >>> + if (cache_id < 0) >>> + return -ENOENT; >>> >>> lockdep_assert_cpus_held(); >>> >> >> > >