[PATCH hyperv-next v3] arch/x86: Provide the CPU number in the wakeup AP callback
From: Roman Kisel
Date: Wed Apr 30 2025 - 16:48:34 EST
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@xxxxxxxxxxx>
Signed-off-by: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
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-romank@xxxxxxxxxxxxxxxxxxx/
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-romank@xxxxxxxxxxxxxxxxxxx/
- 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-romank@xxxxxxxxxxxxxxxxxxx/
---
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