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    Subject[PATCH 14/26] x86/acpi, x86/boot: Add multiprocessor wake-up support
    Date
    From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

    TDX cannot use INIT/SIPI protocol to bring up secondary CPUs because it
    requires assistance from untrusted VMM.

    For platforms that do not support SIPI/INIT, ACPI defines a wakeup
    model (using mailbox) via MADT multiprocessor wakeup structure. More
    details about it can be found in ACPI specification v6.4, the section
    titled "Multiprocessor Wakeup Structure". If a platform firmware
    produces the multiprocessor wakeup structure, then OS may use this
    new mailbox-based mechanism to wake up the APs.

    Add ACPI MADT wake structure parsing support for x86 platform and if
    MADT wake table is present, update apic->wakeup_secondary_cpu_64 with
    new API which uses MADT wake mailbox to wake-up CPU.

    Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
    Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
    Reviewed-by: Andi Kleen <ak@linux.intel.com>
    Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    ---
    arch/x86/include/asm/apic.h | 5 ++
    arch/x86/kernel/acpi/boot.c | 114 ++++++++++++++++++++++++++++++++++++
    arch/x86/kernel/apic/apic.c | 10 ++++
    3 files changed, 129 insertions(+)

    diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
    index 35006e151774..bd8ae0a7010a 100644
    --- a/arch/x86/include/asm/apic.h
    +++ b/arch/x86/include/asm/apic.h
    @@ -490,6 +490,11 @@ static inline unsigned int read_apic_id(void)
    return apic->get_apic_id(reg);
    }

    +#ifdef CONFIG_X86_64
    +typedef int (*wakeup_cpu_handler)(int apicid, unsigned long start_eip);
    +extern void acpi_wake_cpu_handler_update(wakeup_cpu_handler handler);
    +#endif
    +
    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 5b6d1a95776f..af204a217575 100644
    --- a/arch/x86/kernel/acpi/boot.c
    +++ b/arch/x86/kernel/acpi/boot.c
    @@ -65,6 +65,15 @@ static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
    static bool acpi_support_online_capable;
    #endif

    +#ifdef CONFIG_X86_64
    +/* Physical address of the Multiprocessor Wakeup Structure mailbox */
    +static u64 acpi_mp_wake_mailbox_paddr;
    +/* Virtual address of the Multiprocessor Wakeup Structure mailbox */
    +static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox;
    +/* Lock to protect mailbox (acpi_mp_wake_mailbox) from parallel access */
    +static DEFINE_SPINLOCK(mailbox_lock);
    +#endif
    +
    #ifdef CONFIG_X86_IO_APIC
    /*
    * Locks related to IOAPIC hotplug
    @@ -336,6 +345,80 @@ acpi_parse_lapic_nmi(union acpi_subtable_headers * header, const unsigned long e
    return 0;
    }

    +#ifdef CONFIG_X86_64
    +/* Virtual address of the Multiprocessor Wakeup Structure mailbox */
    +static int acpi_wakeup_cpu(int apicid, unsigned long start_ip)
    +{
    + static physid_mask_t apic_id_wakemap = PHYSID_MASK_NONE;
    + unsigned long flags;
    + u8 timeout;
    +
    + /* 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, section titled
    + * "Multiprocessor Wakeup Structure" the mailbox-based wakeup
    + * mechanism cannot be used more than once for the same CPU.
    + * Skip wakeups if they are attempted more than once.
    + */
    + if (physid_isset(apicid, apic_id_wakemap)) {
    + pr_err("CPU already awake (APIC ID %x), skipping wakeup\n",
    + apicid);
    + return -EINVAL;
    + }
    +
    + spin_lock_irqsave(&mailbox_lock, flags);
    +
    + /*
    + * 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.
    + *
    + * The value of apic_id and wakeup_vector has to be set before updating
    + * the wakeup command. To let compiler preserve order of writes, use
    + * smp_store_release.
    + */
    + 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 the 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: 0xFF as timeout value is decided based on our experiments.
    + *
    + * XXX: Change the timeout once ACPI specification comes up with
    + * standard maximum timeout value.
    + */
    + timeout = 0xFF;
    + while (READ_ONCE(acpi_mp_wake_mailbox->command) && --timeout)
    + cpu_relax();
    +
    + /* If timed out (timeout == 0), return error */
    + if (!timeout) {
    + spin_unlock_irqrestore(&mailbox_lock, flags);
    + return -EIO;
    + }
    +
    + /*
    + * 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);
    +
    + spin_unlock_irqrestore(&mailbox_lock, flags);
    +
    + return 0;
    +}
    +#endif
    #endif /*CONFIG_X86_LOCAL_APIC */

    #ifdef CONFIG_X86_IO_APIC
    @@ -1083,6 +1166,29 @@ static int __init acpi_parse_madt_lapic_entries(void)
    }
    return 0;
    }
    +
    +#ifdef CONFIG_X86_64
    +static int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
    + const unsigned long end)
    +{
    + struct acpi_madt_multiproc_wakeup *mp_wake;
    +
    + 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_64 */
    #endif /* CONFIG_X86_LOCAL_APIC */

    #ifdef CONFIG_X86_IO_APIC
    @@ -1278,6 +1384,14 @@ static void __init acpi_process_madt(void)

    smp_found_config = 1;
    }
    +
    +#ifdef CONFIG_X86_64
    + /*
    + * Parse MADT MP Wake entry.
    + */
    + acpi_table_parse_madt(ACPI_MADT_TYPE_MULTIPROC_WAKEUP,
    + acpi_parse_mp_wake, 1);
    +#endif
    }
    if (error == -EINVAL) {
    /*
    diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
    index b70344bf6600..3c8f2c797a98 100644
    --- a/arch/x86/kernel/apic/apic.c
    +++ b/arch/x86/kernel/apic/apic.c
    @@ -2551,6 +2551,16 @@ u32 x86_msi_msg_get_destid(struct msi_msg *msg, bool extid)
    }
    EXPORT_SYMBOL_GPL(x86_msi_msg_get_destid);

    +#ifdef CONFIG_X86_64
    +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_64 = handler;
    +}
    +#endif
    +
    /*
    * Override the generic EOI implementation with an optimized version.
    * Only called during early boot when only one CPU is active and with
    --
    2.32.0
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