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> --- 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). [V2] - 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 | 4 ++-- arch/x86/kernel/acpi/madt_wakeup.c | 2 +- arch/x86/kernel/apic/apic_noop.c | 2 +- arch/x86/kernel/apic/x2apic_uv_x.c | 2 +- arch/x86/kernel/smpboot.c | 8 ++++---- 9 files changed, 18 insertions(+), 35 deletions(-) diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c index 82492efc5d94..e7b6dba30a0a 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, 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..5784b6c56ca4 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, 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..ba744dbc22bb 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, 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..a480f7626847 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, 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, 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, int cpu); + int (*wakeup_secondary_cpu_64)(u32 apicid, unsigned long start_eip, int cpu); }; /* diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h index 07aadf0e839f..abca9d8d4a82 100644 --- a/arch/x86/include/asm/mshyperv.h +++ b/arch/x86/include/asm/mshyperv.h @@ -268,11 +268,11 @@ 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, 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, 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..d95c806f0e93 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, 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..cab7cac16f53 100644 --- a/arch/x86/kernel/apic/apic_noop.c +++ b/arch/x86/kernel/apic/apic_noop.c @@ -27,7 +27,7 @@ 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, 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..f8000555127b 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, int cpu) { unsigned long val; int pnode; diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index c10850ae6f09..4b514e485f9c 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, int cpu) { unsigned long send_status = 0, accept_status = 0; int num_starts, j, maxlvt; @@ -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
