From: Roman Kisel <rom...@linux.microsoft.com> Sent: Wednesday, April 30, 2025 1:47 PM > > When starting APs, confidential guests and paravisor guests > need to know the CPU number, and the pattern of using the linear > search has emerged in several places. With N processors that leads > to the O(N^2) time complexity. > > Provide the CPU number in the AP wake up callback so that one can > get the CPU number in constant time. > > Suggested-by: Michael Kelley <mhkli...@outlook.com> > Signed-off-by: Roman Kisel <rom...@linux.microsoft.com> > Reviewed-by: Tom Lendacky <thomas.lenda...@amd.com>
LGTM. Reviewed-by: Michael Kelley <mhkli...@outlook.com> > --- > The diff in ivm.c might catch your eye but that code mixes up the > APIC ID and the CPU number anyway. That is fixed in another patch: > https://lore.kernel.org/linux-hyperv/20250428182705.132755-1-rom...@linux.microsoft.com/ > independently of this one (being an optimization). > I separated the two as this one might be more disputatious due to > the change in the API (although it is a tiny one and comes with > the benefits). > > [V3] > - Fixed the cpu nummber to be unsigned int within the patch and > in the do_boot_cpu() function. > ** Thank you, Thomas! ** > > [V2] > > https://lore.kernel.org/linux-hyperv/20250430161413.276759-1-rom...@linux.microsoft.com/ > - Remove the struct used in v1 in favor of passing the CPU number > directly to the callback not to increase complexity. > ** Thank you, Michael! ** > [V1] > > https://lore.kernel.org/linux-hyperv/20250428225948.810147-1-rom...@linux.microsoft.com/ > --- > arch/x86/coco/sev/core.c | 13 ++----------- > arch/x86/hyperv/hv_vtl.c | 12 ++---------- > arch/x86/hyperv/ivm.c | 2 +- > arch/x86/include/asm/apic.h | 8 ++++---- > arch/x86/include/asm/mshyperv.h | 5 +++-- > arch/x86/kernel/acpi/madt_wakeup.c | 2 +- > arch/x86/kernel/apic/apic_noop.c | 8 +++++++- > arch/x86/kernel/apic/x2apic_uv_x.c | 2 +- > arch/x86/kernel/smpboot.c | 10 +++++----- > 9 files changed, 26 insertions(+), 36 deletions(-) > > diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c > index 82492efc5d94..8b6d310b61b9 100644 > --- a/arch/x86/coco/sev/core.c > +++ b/arch/x86/coco/sev/core.c > @@ -1179,7 +1179,7 @@ static void snp_cleanup_vmsa(struct sev_es_save_area > *vmsa, int apic_id) > free_page((unsigned long)vmsa); > } > > -static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip) > +static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip, > unsigned int cpu) > { > struct sev_es_save_area *cur_vmsa, *vmsa; > struct ghcb_state state; > @@ -1187,7 +1187,7 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned > long start_ip) > unsigned long flags; > struct ghcb *ghcb; > u8 sipi_vector; > - int cpu, ret; > + int ret; > u64 cr4; > > /* > @@ -1208,15 +1208,6 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, > unsigned long start_ip) > > /* Override start_ip with known protected guest start IP */ > start_ip = real_mode_header->sev_es_trampoline_start; > - > - /* Find the logical CPU for the APIC ID */ > - for_each_present_cpu(cpu) { > - if (arch_match_cpu_phys_id(cpu, apic_id)) > - break; > - } > - if (cpu >= nr_cpu_ids) > - return -EINVAL; > - > cur_vmsa = per_cpu(sev_vmsa, cpu); > > /* > diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c > index 582fe820e29c..4d6e0e198041 100644 > --- a/arch/x86/hyperv/hv_vtl.c > +++ b/arch/x86/hyperv/hv_vtl.c > @@ -237,17 +237,9 @@ static int hv_vtl_apicid_to_vp_id(u32 apic_id) > return ret; > } > > -static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip) > +static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip, > unsigned int cpu) > { > - int vp_id, cpu; > - > - /* Find the logical CPU for the APIC ID */ > - for_each_present_cpu(cpu) { > - if (arch_match_cpu_phys_id(cpu, apicid)) > - break; > - } > - if (cpu >= nr_cpu_ids) > - return -EINVAL; > + int vp_id; > > pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid); > vp_id = hv_vtl_apicid_to_vp_id(apicid); > diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c > index c0039a90e9e0..6025da891a83 100644 > --- a/arch/x86/hyperv/ivm.c > +++ b/arch/x86/hyperv/ivm.c > @@ -288,7 +288,7 @@ static void snp_cleanup_vmsa(struct sev_es_save_area > *vmsa) > free_page((unsigned long)vmsa); > } > > -int hv_snp_boot_ap(u32 cpu, unsigned long start_ip) > +int hv_snp_boot_ap(u32 apic_id, unsigned long start_ip, unsigned int cpu) > { > struct sev_es_save_area *vmsa = (struct sev_es_save_area *) > __get_free_page(GFP_KERNEL | __GFP_ZERO); > diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h > index f21ff1932699..33f677e2db75 100644 > --- a/arch/x86/include/asm/apic.h > +++ b/arch/x86/include/asm/apic.h > @@ -313,9 +313,9 @@ struct apic { > u32 (*get_apic_id)(u32 id); > > /* wakeup_secondary_cpu */ > - int (*wakeup_secondary_cpu)(u32 apicid, unsigned long start_eip); > + int (*wakeup_secondary_cpu)(u32 apicid, unsigned long start_eip, > unsigned int cpu); > /* wakeup secondary CPU using 64-bit wakeup point */ > - int (*wakeup_secondary_cpu_64)(u32 apicid, unsigned long start_eip); > + int (*wakeup_secondary_cpu_64)(u32 apicid, unsigned long start_eip, > unsigned int cpu); > > char *name; > }; > @@ -333,8 +333,8 @@ struct apic_override { > void (*send_IPI_self)(int vector); > u64 (*icr_read)(void); > void (*icr_write)(u32 low, u32 high); > - int (*wakeup_secondary_cpu)(u32 apicid, unsigned long start_eip); > - int (*wakeup_secondary_cpu_64)(u32 apicid, unsigned long start_eip); > + int (*wakeup_secondary_cpu)(u32 apicid, unsigned long start_eip, > unsigned int cpu); > + int (*wakeup_secondary_cpu_64)(u32 apicid, unsigned long start_eip, > unsigned int cpu); > }; > > /* > diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h > index 07aadf0e839f..cab952f722e4 100644 > --- a/arch/x86/include/asm/mshyperv.h > +++ b/arch/x86/include/asm/mshyperv.h > @@ -268,11 +268,12 @@ int hv_unmap_ioapic_interrupt(int ioapic_id, struct > hv_interrupt_entry *entry); > #ifdef CONFIG_AMD_MEM_ENCRYPT > bool hv_ghcb_negotiate_protocol(void); > void __noreturn hv_ghcb_terminate(unsigned int set, unsigned int reason); > -int hv_snp_boot_ap(u32 cpu, unsigned long start_ip); > +int hv_snp_boot_ap(u32 apic_id, unsigned long start_ip, unsigned int cpu); > #else > static inline bool hv_ghcb_negotiate_protocol(void) { return false; } > static inline void hv_ghcb_terminate(unsigned int set, unsigned int reason) > {} > -static inline int hv_snp_boot_ap(u32 cpu, unsigned long start_ip) { return > 0; } > +static inline int hv_snp_boot_ap(u32 apic_id, unsigned long start_ip, > + unsigned int cpu) { return 0; } > #endif > > #if defined(CONFIG_AMD_MEM_ENCRYPT) || defined(CONFIG_INTEL_TDX_GUEST) > diff --git a/arch/x86/kernel/acpi/madt_wakeup.c > b/arch/x86/kernel/acpi/madt_wakeup.c > index d5ef6215583b..f48581888d53 100644 > --- a/arch/x86/kernel/acpi/madt_wakeup.c > +++ b/arch/x86/kernel/acpi/madt_wakeup.c > @@ -169,7 +169,7 @@ static int __init acpi_mp_setup_reset(u64 reset_vector) > return 0; > } > > -static int acpi_wakeup_cpu(u32 apicid, unsigned long start_ip) > +static int acpi_wakeup_cpu(u32 apicid, unsigned long start_ip, unsigned int > cpu) > { > if (!acpi_mp_wake_mailbox_paddr) { > pr_warn_once("No MADT mailbox: cannot bringup secondary CPUs. > Booting with kexec?\n"); > diff --git a/arch/x86/kernel/apic/apic_noop.c > b/arch/x86/kernel/apic/apic_noop.c > index b5bb7a2e8340..58abb941c45b 100644 > --- a/arch/x86/kernel/apic/apic_noop.c > +++ b/arch/x86/kernel/apic/apic_noop.c > @@ -27,7 +27,13 @@ static void noop_send_IPI_allbutself(int vector) { } > static void noop_send_IPI_all(int vector) { } > static void noop_send_IPI_self(int vector) { } > static void noop_apic_icr_write(u32 low, u32 id) { } > -static int noop_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip) { > return -1; } > + > +static int noop_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip, > + unsigned int cpu) > +{ > + return -1; > +} > + > static u64 noop_apic_icr_read(void) { return 0; } > static u32 noop_get_apic_id(u32 apicid) { return 0; } > static void noop_apic_eoi(void) { } > diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c > b/arch/x86/kernel/apic/x2apic_uv_x.c > index 7fef504ca508..15209f220e1f 100644 > --- a/arch/x86/kernel/apic/x2apic_uv_x.c > +++ b/arch/x86/kernel/apic/x2apic_uv_x.c > @@ -667,7 +667,7 @@ static __init void build_uv_gr_table(void) > } > } > > -static int uv_wakeup_secondary(u32 phys_apicid, unsigned long start_rip) > +static int uv_wakeup_secondary(u32 phys_apicid, unsigned long start_rip, > unsigned int cpu) > { > unsigned long val; > int pnode; > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index c10850ae6f09..b013296b100f 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -715,7 +715,7 @@ static void send_init_sequence(u32 phys_apicid) > /* > * Wake up AP by INIT, INIT, STARTUP sequence. > */ > -static int wakeup_secondary_cpu_via_init(u32 phys_apicid, unsigned long > start_eip) > +static int wakeup_secondary_cpu_via_init(u32 phys_apicid, unsigned long > start_eip, unsigned int cpu) > { > unsigned long send_status = 0, accept_status = 0; > int num_starts, j, maxlvt; > @@ -862,7 +862,7 @@ int common_cpu_up(unsigned int cpu, struct task_struct > *idle) > * Returns zero if startup was successfully sent, else error code from > * ->wakeup_secondary_cpu. > */ > -static int do_boot_cpu(u32 apicid, int cpu, struct task_struct *idle) > +static int do_boot_cpu(u32 apicid, unsigned int cpu, struct task_struct > *idle) > { > unsigned long start_ip = real_mode_header->trampoline_start; > int ret; > @@ -916,11 +916,11 @@ static int do_boot_cpu(u32 apicid, int cpu, struct > task_struct *idle) > * - Use an INIT boot APIC message > */ > if (apic->wakeup_secondary_cpu_64) > - ret = apic->wakeup_secondary_cpu_64(apicid, start_ip); > + ret = apic->wakeup_secondary_cpu_64(apicid, start_ip, cpu); > else if (apic->wakeup_secondary_cpu) > - ret = apic->wakeup_secondary_cpu(apicid, start_ip); > + ret = apic->wakeup_secondary_cpu(apicid, start_ip, cpu); > else > - ret = wakeup_secondary_cpu_via_init(apicid, start_ip); > + ret = wakeup_secondary_cpu_via_init(apicid, start_ip, cpu); > > /* If the wakeup mechanism failed, cleanup the warm reset vector */ > if (ret) > > base-commit: 628cc040b3a2980df6032766e8ef0688e981ab95 > -- > 2.43.0 >
