arch/x86: Provide the CPU number in the wakeup AP callback

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 <mhklinux@outlook.com>
Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20250507182227.7421-3-romank@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20250507182227.7421-3-romank@linux.microsoft.com>

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index b0c1a7a574974a297b3078a9c9de942e1dc3434b..7780d55d18336c4faa3266401ed3bf96ec5d488b 100644 (file)
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -1177,7 +1177,7 @@ 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;
@@ -1185,7 +1185,7 @@ 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;
 
        /*
@@ -1206,15 +1206,6 @@ 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 2f32ac1ae40eab0d2f308196c94f94874a7ee59b..3d149a2ca4c87ce8ed41cb1b32279c7837869559 100644 (file)
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -211,17 +211,9 @@ free_lock:
        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_index, 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_index;
 
        pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid);
        vp_index = hv_apicid_to_vp_index(apicid);

diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 0cc239cdb4dad87cd6a518fcb19a19f0d8bf8d22..e21557b24d19279d28c3279e8e78faf8deb8c162 100644 (file)
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -289,7 +289,7 @@ static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa)
                free_page((unsigned long)vmsa);
 }
 
-int hv_snp_boot_ap(u32 apic_id, 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);
@@ -298,7 +298,7 @@ int hv_snp_boot_ap(u32 apic_id, unsigned long start_ip)
        u64 ret, retry = 5;
        struct hv_enable_vp_vtl *start_vp_input;
        unsigned long flags;
-       int cpu, vp_index;
+       int vp_index;
 
        if (!vmsa)
                return -ENOMEM;
@@ -308,17 +308,6 @@ int hv_snp_boot_ap(u32 apic_id, unsigned long start_ip)
        if (vp_index < 0 || vp_index > ms_hyperv.max_vp_index)
                return -EINVAL;
 
-       /*
-        * Find the Linux CPU number for addressing the per-CPU data, and it
-        * might not be the same as APIC ID.
-        */
-       for_each_present_cpu(cpu) {
-               if (arch_match_cpu_phys_id(cpu, apic_id))
-                       break;
-       }
-       if (cpu >= nr_cpu_ids)
-               return -EINVAL;
-
        native_store_gdt(&gdtr);
 
        vmsa->gdtr.base = gdtr.address;

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index c903d358405d389b808c6075cf6bfa6032710c2a..eaf43d44620357cc7d525cc033bfd5009544b264 100644 (file)
--- 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 0b9a3a307d06554452131709fbeb501cc08d09e5..5ec92e3e2e37655af0604cd6259f0fbf92c51c58 100644 (file)
--- 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 apic_id, 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 apic_id, 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 f36f28405dcc63abfef5ee089022c4ef159907d9..6d7603511f52c38b0290f600a94df046defb7a3a 100644 (file)
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -126,7 +126,7 @@ 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 b5bb7a2e8340b20db3a04e3f4e1684e6c4404b45..58abb941c45bec715cb4e0830e120f168f72ca66 100644 (file)
--- 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/apic_numachip.c b/arch/x86/kernel/apic/apic_numachip.c
index 16410f087b7af4f8390ee4973d9ee4bbd5679827..333536b89bde3dff9d25272049c9537a8d2cc501 100644 (file)
--- a/arch/x86/kernel/apic/apic_numachip.c
+++ b/arch/x86/kernel/apic/apic_numachip.c
@@ -56,7 +56,7 @@ static void numachip2_apic_icr_write(int apicid, unsigned int val)
        numachip2_write32_lcsr(NUMACHIP2_APIC_ICR, (apicid << 12) | val);
 }
 
-static int numachip_wakeup_secondary(u32 phys_apicid, unsigned long start_rip)
+static int numachip_wakeup_secondary(u32 phys_apicid, unsigned long start_rip, unsigned int cpu)
 {
        numachip_apic_icr_write(phys_apicid, APIC_DM_INIT);
        numachip_apic_icr_write(phys_apicid, APIC_DM_STARTUP |

diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index 7fef504ca508b7829b89a3ca2dad9be1e22860e9..15209f220e1fda33feaea789312e94747a01911d 100644 (file)
--- 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 d6cf1e23c2a32677a40db13b8d0166b705d0d83f..d52e9238e9fd135ecc52cca8ab28fcb3d9d7aad4 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -695,7 +695,7 @@ 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;
@@ -842,7 +842,7 @@ 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;
@@ -896,11 +896,11 @@ 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)