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Message-ID: <2592439.mvXUDI8C0e@kreacher>
Date: Mon, 24 May 2021 16:51:33 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Len Brown <lenb@...nel.org>,
Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
Sean Christopherson <seanjc@...gle.com>,
Andi Kleen <ak@...ux.intel.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/1] x86/acpi, x86/boot: Add multiprocessor wake-up support
On Monday, May 24, 2021 8:02:21 AM CEST Kuppuswamy Sathyanarayanan wrote:
> As per ACPI specification r6.4, sec 5.2.12.19, a new sub
> structure – multiprocessor wake-up structure - is added to the
> ACPI Multiple APIC Description Table (MADT) to describe the
> information of the mailbox. If a platform firmware produces the
> multiprocessor wake-up structure, then OS may use this new
> mailbox-based mechanism to wake up the APs.
>
> Add ACPI MADT wake table parsing support for x86 platform and if
> MADT wake table is present, update apic->wakeup_secondary_cpu with
> new API which uses MADT wake mailbox to wake-up CPU.
>
> Co-developed-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> Reviewed-by: Andi Kleen <ak@...ux.intel.com>
It would help if you CCed this to linux-acpi@...r.kernel.org.
> ---
>
> Changes since v4:
> * Used smp_store_release() in place of WRITE_ONCE().
> * Addressed some checkpatch warnings.
>
> Changes since v3:
> * Removed acpi_mp_wake_mailbox_init() and moved init code to
> acpi_wakeup_cpu().
> * Removed redundant NULL pointer check for acpi_mp_wake_mailbox.
> * Added comments/debug prints as per Rafael's suggestion.
> * Removed MADT/SVKL ACPI patches from this patchset. It will be
> merged via ACPICA submission.
>
> arch/x86/include/asm/apic.h | 3 ++
> arch/x86/kernel/acpi/boot.c | 96 +++++++++++++++++++++++++++++++++++++
> arch/x86/kernel/apic/apic.c | 8 ++++
> 3 files changed, 107 insertions(+)
>
> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
> index 412b51e059c8..3e94e1f402ea 100644
> --- a/arch/x86/include/asm/apic.h
> +++ b/arch/x86/include/asm/apic.h
> @@ -487,6 +487,9 @@ static inline unsigned int read_apic_id(void)
> return apic->get_apic_id(reg);
> }
>
> +typedef int (*wakeup_cpu_handler)(int apicid, unsigned long start_eip);
> +extern void acpi_wake_cpu_handler_update(wakeup_cpu_handler handler);
> +
> extern int default_apic_id_valid(u32 apicid);
> extern int default_acpi_madt_oem_check(char *, char *);
> extern void default_setup_apic_routing(void);
> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> index 14cd3186dc77..c51134eb55d0 100644
> --- a/arch/x86/kernel/acpi/boot.c
> +++ b/arch/x86/kernel/acpi/boot.c
> @@ -65,6 +65,10 @@ int acpi_fix_pin2_polarity __initdata;
> static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
> #endif
>
> +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
> /*
> * Locks related to IOAPIC hotplug
> @@ -329,6 +333,68 @@ acpi_parse_lapic_nmi(union acpi_subtable_headers * header, const unsigned long e
> return 0;
> }
>
> +static int acpi_wakeup_cpu(int apicid, unsigned long start_ip)
> +{
> + u8 timeout = 0xFF;
> +
> + /* Remap mailbox memory only for the first call to acpi_wakeup_cpu() */
> + if (physids_empty(apic_id_wakemap)) {
> + acpi_mp_wake_mailbox = memremap(acpi_mp_wake_mailbox_paddr,
> + sizeof(*acpi_mp_wake_mailbox),
> + MEMREMAP_WB);
> + }
> +
> + /*
> + * According to the ACPI specification r6.4, sec 5.2.12.19, the
> + * mailbox-based wakeup mechanism cannot be used more than once
> + * for the same CPU, so skip sending wake commands to already
> + * awake CPU.
> + */
> + if (physid_isset(apicid, apic_id_wakemap)) {
> + pr_err("CPU already awake (APIC ID %x), skipping wakeup\n",
> + apicid);
> + return -EINVAL;
> + }
> +
> + /*
> + * Mailbox memory is shared between firmware and OS. Firmware will
> + * listen on mailbox command address, and once it receives the wakeup
> + * command, CPU associated with the given apicid will be booted. So,
> + * the value of apic_id and wakeup_vector has to be set before updating
> + * the wakeup command. So use smp_store_release to let the compiler know
> + * about it and preserve the order of writes.
> + */
> + smp_store_release(&acpi_mp_wake_mailbox->apic_id, apicid);
> + smp_store_release(&acpi_mp_wake_mailbox->wakeup_vector, start_ip);
> + smp_store_release(&acpi_mp_wake_mailbox->command,
> + ACPI_MP_WAKE_COMMAND_WAKEUP);
> +
> + /*
> + * After writing wakeup command, wait for maximum timeout of 0xFF
> + * for firmware to reset the command address back zero to indicate
> + * the successful reception of command.
> + * NOTE: 255 as timeout value is decided based on our experiments.
> + *
> + * XXX: Change the timeout once ACPI specification comes up with
> + * standard maximum timeout value.
> + */
> + while (READ_ONCE(acpi_mp_wake_mailbox->command) && timeout--)
> + cpu_relax();
> +
> + 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;
> +}
> +
> #endif /*CONFIG_X86_LOCAL_APIC */
>
> #ifdef CONFIG_X86_IO_APIC
> @@ -1086,6 +1152,30 @@ static int __init acpi_parse_madt_lapic_entries(void)
> }
> return 0;
> }
> +
> +static int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
> + const unsigned long end)
> +{
> + struct acpi_madt_multiproc_wakeup *mp_wake;
> +
> + if (acpi_mp_wake_mailbox)
> + return -EINVAL;
> +
> + if (!IS_ENABLED(CONFIG_SMP))
> + return -ENODEV;
> +
> + mp_wake = (struct acpi_madt_multiproc_wakeup *)header;
> + if (BAD_MADT_ENTRY(mp_wake, end))
> + return -EINVAL;
> +
> + acpi_table_print_madt_entry(&header->common);
> +
> + acpi_mp_wake_mailbox_paddr = mp_wake->base_address;
> +
> + acpi_wake_cpu_handler_update(acpi_wakeup_cpu);
> +
> + return 0;
> +}
> #endif /* CONFIG_X86_LOCAL_APIC */
>
> #ifdef CONFIG_X86_IO_APIC
> @@ -1284,6 +1374,12 @@ static void __init acpi_process_madt(void)
>
> smp_found_config = 1;
> }
> +
> + /*
> + * Parse MADT MP Wake entry.
> + */
> + acpi_table_parse_madt(ACPI_MADT_TYPE_MULTIPROC_WAKEUP,
> + acpi_parse_mp_wake, 1);
> }
> if (error == -EINVAL) {
> /*
> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> index 4f26700f314d..f1b90a4b89e8 100644
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -2554,6 +2554,14 @@ u32 x86_msi_msg_get_destid(struct msi_msg *msg, bool extid)
> }
> EXPORT_SYMBOL_GPL(x86_msi_msg_get_destid);
>
> +void __init acpi_wake_cpu_handler_update(wakeup_cpu_handler handler)
> +{
> + struct apic **drv;
> +
> + for (drv = __apicdrivers; drv < __apicdrivers_end; drv++)
> + (*drv)->wakeup_secondary_cpu = handler;
> +}
> +
> /*
> * Override the generic EOI implementation with an optimized version.
> * Only called during early boot when only one CPU is active and with
>
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