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[31.30.173.16]) by smtp.gmail.com with ESMTPSA id h3-20020a5d5043000000b002c70ce264bfsm18081249wrt.76.2023.04.27.03.25.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Apr 2023 03:25:48 -0700 (PDT) Date: Thu, 27 Apr 2023 12:25:42 +0200 From: Andrew Jones To: Sunil V L Cc: Palmer Dabbelt , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-acpi@vger.kernel.org, linux-crypto@vger.kernel.org, platform-driver-x86@vger.kernel.org, llvm@lists.linux.dev, corbet@lwn.net, Paul Walmsley , aou@eecs.berkeley.edu, lenb@kernel.org, daniel.lezcano@linaro.org, tglx@linutronix.de, qianweili@huawei.com, wangzhou1@hisilicon.com, herbert@gondor.apana.org.au, Marc Zyngier , luzmaximilian@gmail.com, hdegoede@redhat.com, markgross@kernel.org, nathan@kernel.org, ndesaulniers@google.com, trix@redhat.com, rafael@kernel.org, davem@davemloft.net, rafael.j.wysocki@intel.com Subject: Re: [PATCH V4 08/23] RISC-V: ACPI: Cache and retrieve the RINTC structure Message-ID: References: <20230404182037.863533-9-sunilvl@ventanamicro.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: platform-driver-x86@vger.kernel.org On Thu, Apr 27, 2023 at 02:52:50PM +0530, Sunil V L wrote: > Hi Palmer, > > On Wed, Apr 26, 2023 at 11:45:00AM -0700, Palmer Dabbelt wrote: > > On Tue, 04 Apr 2023 11:20:22 PDT (-0700), sunilvl@ventanamicro.com wrote: > > > RINTC structures in the MADT provide mapping between the hartid > > > and the CPU. This is required many times even at run time like > > > cpuinfo. So, instead of parsing the ACPI table every time, cache > > > the RINTC structures and provide a function to get the correct > > > RINTC structure for a given cpu. > > > > > > Signed-off-by: Sunil V L > > > Acked-by: Rafael J. Wysocki > > > --- > > > arch/riscv/include/asm/acpi.h | 2 ++ > > > arch/riscv/kernel/acpi.c | 60 +++++++++++++++++++++++++++++++++++ > > > 2 files changed, 62 insertions(+) > > > > > > diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h > > > index 9be52b6ffae1..1606dce8992e 100644 > > > --- a/arch/riscv/include/asm/acpi.h > > > +++ b/arch/riscv/include/asm/acpi.h > > > @@ -59,6 +59,8 @@ static inline bool acpi_has_cpu_in_madt(void) > > > > > > static inline void arch_fix_phys_package_id(int num, u32 slot) { } > > > > > > +struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu); > > > +u32 get_acpi_id_for_cpu(int cpu); > > > #endif /* CONFIG_ACPI */ > > > > > > #endif /*_ASM_ACPI_H*/ > > > diff --git a/arch/riscv/kernel/acpi.c b/arch/riscv/kernel/acpi.c > > > index 81d448c41714..40ab55309c70 100644 > > > --- a/arch/riscv/kernel/acpi.c > > > +++ b/arch/riscv/kernel/acpi.c > > > @@ -24,6 +24,66 @@ EXPORT_SYMBOL(acpi_disabled); > > > int acpi_pci_disabled = 1; /* skip ACPI PCI scan and IRQ initialization */ > > > EXPORT_SYMBOL(acpi_pci_disabled); > > > > > > +static struct acpi_madt_rintc cpu_madt_rintc[NR_CPUS]; > > > + > > > +static int acpi_parse_madt_rintc(union acpi_subtable_headers *header, const unsigned long end) > > > +{ > > > + struct acpi_madt_rintc *rintc = (struct acpi_madt_rintc *)header; > > > + int cpuid; > > > + > > > + if (!(rintc->flags & ACPI_MADT_ENABLED)) > > > + return 0; > > > + > > > + cpuid = riscv_hartid_to_cpuid(rintc->hart_id); > > > > Unless I'm missing something, this races with CPUs coming online. Maybe > > that's a rare enough case we don't care, but I think we'd also just have > > simpler logic if we fixed it... > > > This depend only on cpuid_to_hartid_map filled up. I wish I could > initialize this RINTC mapping in setup_smp() itself like ARM64. But in > RISC-V, this file smpboot.c gets built only when CONFIG_SMP is enabled. > Hence, we need to initialize this array outside of setup_smp(). > > I can update the code to initialize this from setup_arch() immediately > after setup_smp() if ACPI is enabled. That should avoid the global > variable check also. Let me know if you prefer this. > > > > + /* > > > + * When CONFIG_SMP is disabled, mapping won't be created for > > > + * all cpus. > > > + * CPUs more than NR_CPUS, will be ignored. > > > + */ > > > + if (cpuid >= 0 && cpuid < NR_CPUS) > > > + cpu_madt_rintc[cpuid] = *rintc; > > > + > > > + return 0; > > > +} > > > + > > > +static int acpi_init_rintc_array(void) > > > +{ > > > + if (acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC, acpi_parse_madt_rintc, 0) > 0) > > > + return 0; > > > + > > > + return -ENODEV; > > > +} > > > + > > > +/* > > > + * Instead of parsing (and freeing) the ACPI table, cache > > > + * the RINTC structures since they are frequently used > > > + * like in cpuinfo. > > > + */ > > > +struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu) > > > +{ > > > + static bool rintc_init_done; > > > > ... basically just get rid of this global variable, and instead have a > > > > if (!&cpu_madt_rintc[cpu]) > > ... parse ... > > return &cpu_madt_rintc[cpu]; > > > > that'd probably let us get rid of a handful of these helpers too, as now > > it's just a call to the parsing bits. > > > I am afraid this (!&cpu_madt_rintc[cpu]) check won't work since we are > not caching the RINTC pointers but actual contents itself. So, the > address is always valid. However, as per Drew's earlier feedback I am > going to reduce one helper. I am planning to send the next version of > this patch once 6.4 rc1 is available since the ACPICA patches are merged > now. > > > > + > > > + if (!rintc_init_done) { > > > + if (acpi_init_rintc_array()) { > > > + pr_err("No valid RINTC entries exist\n"); > > > + return NULL; > > > + } > > > + > > > + rintc_init_done = true; > > > + } > > > + > > > + return &cpu_madt_rintc[cpu]; > > > +} > > > + > > > +u32 get_acpi_id_for_cpu(int cpu) > > > +{ > > > + struct acpi_madt_rintc *rintc = acpi_cpu_get_madt_rintc(cpu); > > > + > > > + BUG_ON(!rintc); > > > > We should have some better error reporting here. It looks like all the > > callerss of get_acpi_id_for_cpu() are tolerant of a nonsense ID being > > returned, so maybe we just pr_warn() something users can understand and then > > return -1 or something? > > > > RINTC is mandatory for ACPI systems. Also, all 32bit values are valid > for UID. So, there is no bogus value we can return. > > Actually, I just realized this check is redundant. It will never be NULL > since it is a static array. So, we can just get rid of the BUG. It can be NULL on the first call of acpi_cpu_get_madt_rintc(), which is a good time to BUG if there's isn't an RINTC. Thanks, drew