mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-08-05 16:54:27 +00:00
43cb39ad26
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>
80 lines
2.3 KiB
C
80 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* NOOP APIC driver.
|
|
*
|
|
* Does almost nothing and should be substituted by a real apic driver via
|
|
* probe routine.
|
|
*
|
|
* Though in case if apic is disabled (for some reason) we try
|
|
* to not uglify the caller's code and allow to call (some) apic routines
|
|
* like self-ipi, etc...
|
|
*
|
|
* FIXME: Remove this gunk. The above argument which was intentionally left
|
|
* in place is silly to begin with because none of the callbacks except for
|
|
* APIC::read/write() have a WARN_ON_ONCE() in them. Sigh...
|
|
*/
|
|
#include <linux/cpumask.h>
|
|
#include <linux/thread_info.h>
|
|
|
|
#include <asm/apic.h>
|
|
|
|
#include "local.h"
|
|
|
|
static void noop_send_IPI(int cpu, int vector) { }
|
|
static void noop_send_IPI_mask(const struct cpumask *cpumask, int vector) { }
|
|
static void noop_send_IPI_mask_allbutself(const struct cpumask *cpumask, int vector) { }
|
|
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,
|
|
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) { }
|
|
|
|
static u32 noop_apic_read(u32 reg)
|
|
{
|
|
WARN_ON_ONCE(boot_cpu_has(X86_FEATURE_APIC) && !apic_is_disabled);
|
|
return 0;
|
|
}
|
|
|
|
static void noop_apic_write(u32 reg, u32 val)
|
|
{
|
|
WARN_ON_ONCE(boot_cpu_has(X86_FEATURE_APIC) && !apic_is_disabled);
|
|
}
|
|
|
|
struct apic apic_noop __ro_after_init = {
|
|
.name = "noop",
|
|
|
|
.dest_mode_logical = true,
|
|
|
|
.disable_esr = 0,
|
|
|
|
.cpu_present_to_apicid = default_cpu_present_to_apicid,
|
|
|
|
.max_apic_id = 0xFE,
|
|
.get_apic_id = noop_get_apic_id,
|
|
|
|
.calc_dest_apicid = apic_flat_calc_apicid,
|
|
|
|
.send_IPI = noop_send_IPI,
|
|
.send_IPI_mask = noop_send_IPI_mask,
|
|
.send_IPI_mask_allbutself = noop_send_IPI_mask_allbutself,
|
|
.send_IPI_allbutself = noop_send_IPI_allbutself,
|
|
.send_IPI_all = noop_send_IPI_all,
|
|
.send_IPI_self = noop_send_IPI_self,
|
|
|
|
.wakeup_secondary_cpu = noop_wakeup_secondary_cpu,
|
|
|
|
.read = noop_apic_read,
|
|
.write = noop_apic_write,
|
|
.eoi = noop_apic_eoi,
|
|
.icr_read = noop_apic_icr_read,
|
|
.icr_write = noop_apic_icr_write,
|
|
};
|