From: "Rafael J. Wysocki" <rafael@kernel.org> To: "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com> Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Andi Kleen <ak@linux.intel.com>, Rafael J Wysocki <rjw@rjwysocki.net>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>, Peter Zijlstra <peterz@infradead.org>, Len Brown <lenb@kernel.org>, Robert Moore <robert.moore@intel.com>, Erik Kaneda <erik.kaneda@intel.com>, ACPI Devel Maling List <linux-acpi@vger.kernel.org>, "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" <devel@acpica.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, "the arch/x86 maintainers" <x86@kernel.org>, Sean Christopherson <sean.j.christopherson@intel.com> Subject: Re: [PATCH v3 3/3] x86/acpi, x86/boot: Add multiprocessor wake-up support Date: Tue, 11 May 2021 12:45:17 +0200 [thread overview] Message-ID: <CAJZ5v0hFfVCm25wUCetOm4YdZKwt5h2jknN9ad1nnpxuR16KkQ@mail.gmail.com> (raw) In-Reply-To: <bc14b461-6431-c5ce-7117-854af8454900@linux.intel.com> On Mon, May 10, 2021 at 11:15 PM Kuppuswamy, Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> wrote: > > > > On 5/10/21 10:24 AM, Rafael J. Wysocki wrote: > > The wakeup function can return an error when it is called for the > > second time on the same CPU. > > To do this, we can only maintain the wakeup status of the CPUs. Can > you check whether following physid_mask based status maintenance is > acceptable? It would work for me except for a couple of nits below. > --- a/arch/x86/kernel/acpi/boot.c > +++ b/arch/x86/kernel/acpi/boot.c > @@ -67,6 +67,7 @@ static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE; > > static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox; > static u64 acpi_mp_wake_mailbox_paddr; > +static physid_mask_t apic_id_wakemap = PHYSID_MASK_NONE; > > #ifdef CONFIG_X86_IO_APIC > /* > @@ -347,6 +348,13 @@ static int acpi_wakeup_cpu(int apicid, unsigned long start_ip) > > acpi_mp_wake_mailbox_init(); > > + /* Check if the given CPU (apicid) is already awake */ The reason why is that the wakeup mechanism used here is only usable once per CPU by the spec, so I would add this information to the comment. Maybe something like "According to the ACPI specification (ACPI 6.4, Section ...), the mailbox-based wakeup mechanism cannot be used more than once for the same CPU, so avoid doing that." > + if (physid_isset(apicid, apic_id_wakemap)) { > + pr_err("APIC ID %x is already awake, so failed to wakeup\n", > + apicid); And I would reword the message like this "CPU already awake (APIC ID %x), skipping wakeup\n". > + return -EINVAL; > + } > + > if (!acpi_mp_wake_mailbox) Note, though, that instead of having this additional flag, you may as well create a mask that is fully populated initially and clear the IDs of the woken-up CPUs in it. Then, you'd only need one check here instead of two. > return -EINVAL; > > @@ -374,8 +382,18 @@ static int acpi_wakeup_cpu(int apicid, unsigned long start_ip) > while (READ_ONCE(acpi_mp_wake_mailbox->command) && timeout--) > cpu_relax(); > > - /* If timedout, return error */ > - return timeout ? 0 : -EIO; > + if (timeout) { > + /* > + * If the CPU wakeup process is successful, store the > + * status in apic_id_wakemap to prevent re-wakeup > + * requests. > + */ > + physid_set(apicid, apic_id_wakemap); > + return 0; > + } > + > + /* If timed out (timeout == 0), return error */ > + return -EIO; > } > > > -- > Sathyanarayanan Kuppuswamy > Linux Kernel Developer
WARNING: multiple messages have this Message-ID (diff)
From: Rafael J. Wysocki <rafael at kernel.org> To: devel@acpica.org Subject: [Devel] Re: [PATCH v3 3/3] x86/acpi, x86/boot: Add multiprocessor wake-up support Date: Tue, 11 May 2021 12:45:17 +0200 [thread overview] Message-ID: <CAJZ5v0hFfVCm25wUCetOm4YdZKwt5h2jknN9ad1nnpxuR16KkQ@mail.gmail.com> (raw) In-Reply-To: bc14b461-6431-c5ce-7117-854af8454900@linux.intel.com [-- Attachment #1: Type: text/plain, Size: 2852 bytes --] On Mon, May 10, 2021 at 11:15 PM Kuppuswamy, Sathyanarayanan <sathyanarayanan.kuppuswamy(a)linux.intel.com> wrote: > > > > On 5/10/21 10:24 AM, Rafael J. Wysocki wrote: > > The wakeup function can return an error when it is called for the > > second time on the same CPU. > > To do this, we can only maintain the wakeup status of the CPUs. Can > you check whether following physid_mask based status maintenance is > acceptable? It would work for me except for a couple of nits below. > --- a/arch/x86/kernel/acpi/boot.c > +++ b/arch/x86/kernel/acpi/boot.c > @@ -67,6 +67,7 @@ static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE; > > static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox; > static u64 acpi_mp_wake_mailbox_paddr; > +static physid_mask_t apic_id_wakemap = PHYSID_MASK_NONE; > > #ifdef CONFIG_X86_IO_APIC > /* > @@ -347,6 +348,13 @@ static int acpi_wakeup_cpu(int apicid, unsigned long start_ip) > > acpi_mp_wake_mailbox_init(); > > + /* Check if the given CPU (apicid) is already awake */ The reason why is that the wakeup mechanism used here is only usable once per CPU by the spec, so I would add this information to the comment. Maybe something like "According to the ACPI specification (ACPI 6.4, Section ...), the mailbox-based wakeup mechanism cannot be used more than once for the same CPU, so avoid doing that." > + if (physid_isset(apicid, apic_id_wakemap)) { > + pr_err("APIC ID %x is already awake, so failed to wakeup\n", > + apicid); And I would reword the message like this "CPU already awake (APIC ID %x), skipping wakeup\n". > + return -EINVAL; > + } > + > if (!acpi_mp_wake_mailbox) Note, though, that instead of having this additional flag, you may as well create a mask that is fully populated initially and clear the IDs of the woken-up CPUs in it. Then, you'd only need one check here instead of two. > return -EINVAL; > > @@ -374,8 +382,18 @@ static int acpi_wakeup_cpu(int apicid, unsigned long start_ip) > while (READ_ONCE(acpi_mp_wake_mailbox->command) && timeout--) > cpu_relax(); > > - /* If timedout, return error */ > - return timeout ? 0 : -EIO; > + if (timeout) { > + /* > + * If the CPU wakeup process is successful, store the > + * status in apic_id_wakemap to prevent re-wakeup > + * requests. > + */ > + physid_set(apicid, apic_id_wakemap); > + return 0; > + } > + > + /* If timed out (timeout == 0), return error */ > + return -EIO; > } > > > -- > Sathyanarayanan Kuppuswamy > Linux Kernel Developer
next prev parent reply other threads:[~2021-05-11 10:45 UTC|newest] Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-26 2:39 [PATCH v3 0/3] Add multiprocessor wake-up support Kuppuswamy Sathyanarayanan 2021-04-26 2:39 ` [PATCH v3 1/3] ACPICA: ACPI 6.4: MADT: add Multiprocessor Wakeup Mailbox Structure Kuppuswamy Sathyanarayanan 2021-04-26 2:39 ` [PATCH v3 2/3] ACPI/table: Print MADT Wake table information Kuppuswamy Sathyanarayanan 2021-04-26 2:39 ` [PATCH v3 3/3] x86/acpi, x86/boot: Add multiprocessor wake-up support Kuppuswamy Sathyanarayanan 2021-05-10 16:32 ` Kuppuswamy, Sathyanarayanan 2021-05-10 16:55 ` Rafael J. Wysocki 2021-05-10 16:55 ` [Devel] " Rafael J. Wysocki 2021-05-10 17:10 ` Kuppuswamy, Sathyanarayanan 2021-05-10 17:22 ` Andi Kleen 2021-05-10 17:24 ` Rafael J. Wysocki 2021-05-10 17:24 ` [Devel] " Rafael J. Wysocki 2021-05-10 21:15 ` Kuppuswamy, Sathyanarayanan 2021-05-11 10:45 ` Rafael J. Wysocki [this message] 2021-05-11 10:45 ` [Devel] " Rafael J. Wysocki 2021-05-13 21:37 ` [PATCH v4 1/1] " Kuppuswamy Sathyanarayanan 2021-05-21 14:18 ` Kuppuswamy, Sathyanarayanan 2021-05-21 14:45 ` Peter Zijlstra 2021-05-21 15:14 ` Kuppuswamy, Sathyanarayanan 2021-05-24 6:02 ` [PATCH v5 " Kuppuswamy Sathyanarayanan 2021-05-24 6:40 ` Mika Penttilä 2021-05-24 13:42 ` Kuppuswamy, Sathyanarayanan 2021-05-24 14:51 ` Rafael J. Wysocki 2021-05-24 15:35 ` Kuppuswamy, Sathyanarayanan 2021-05-10 17:23 ` [PATCH v3 3/3] " Rafael J. Wysocki 2021-05-10 17:23 ` [Devel] " Rafael J. Wysocki
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