Messages in this thread | | | From | "Huang, Kai" <> | Subject | Re: [PATCHv2 11/13] x86/acpi: Do not attempt to bring up secondary CPUs in kexec case | Date | Tue, 24 Oct 2023 10:14:51 +0000 |
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On Fri, 2023-10-20 at 18:12 +0300, Kirill A. Shutemov wrote: > ACPI MADT doesn't allow to offline CPU after it got woke up. It limits > kexec: the second kernel won't be able to use more than one CPU. > > Now acpi_mp_wake_mailbox_paddr already has the mailbox address. > The acpi_wakeup_cpu() will use it to bring up secondary cpus. > > Zero out mailbox address in the ACPI MADT wakeup structure to indicate > that the mailbox is not usable. This prevents the kexec()-ed kernel > from reading a vaild mailbox, which in turn makes the kexec()-ed kernel > only be able to use the boot CPU. > > This is Linux-specific protocol and not reflected in ACPI spec. > > Booting the second kernel with signle CPU is enough to cover the most > common case for kexec -- kdump. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
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