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linux/arch/x86/entry/entry_fred.c
Jacob Pan 1b03d82ba1 x86/irq: Install posted MSI notification handler 
All MSI vectors are multiplexed into a single notification vector when
posted MSI is enabled. It is the responsibility of the notification vector
handler to demultiplex MSI vectors. In the handler the MSI vector handlers
are dispatched without IDT delivery for each pending MSI interrupt.

For example, the interrupt flow will change as follows:
(3 MSIs of different vectors arrive in a a high frequency burst)

BEFORE:
interrupt(MSI)
    irq_enter()
    handler() /* EOI */
    irq_exit()
        process_softirq()
interrupt(MSI)
    irq_enter()
    handler() /* EOI */
    irq_exit()
        process_softirq()
interrupt(MSI)
    irq_enter()
    handler() /* EOI */
    irq_exit()
        process_softirq()

AFTER:
interrupt /* Posted MSI notification vector */
    irq_enter()
	atomic_xchg(PIR)
	handler()
	handler()
	handler()
	pi_clear_on()
    apic_eoi()
    irq_exit()
        process_softirq()

Except for the leading MSI, CPU notifications are skipped/coalesced.

For MSIs which arrive at a low frequency, the demultiplexing loop does not
wait for more interrupts to coalesce. Therefore, there's no additional
latency other than the processing time.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240423174114.526704-9-jacob.jun.pan@linux.intel.com
2024-04-30 00:54:42 +02:00

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* The FRED specific kernel/user entry functions which are invoked from
* assembly code and dispatch to the associated handlers.
*/
#include <linux/kernel.h>
#include <linux/kdebug.h>
#include <linux/nospec.h>
#include <asm/desc.h>
#include <asm/fred.h>
#include <asm/idtentry.h>
#include <asm/syscall.h>
#include <asm/trapnr.h>
#include <asm/traps.h>
/* FRED EVENT_TYPE_OTHER vector numbers */
#define FRED_SYSCALL 1
#define FRED_SYSENTER 2
static noinstr void fred_bad_type(struct pt_regs *regs, unsigned long error_code)
{
irqentry_state_t irq_state = irqentry_nmi_enter(regs);
instrumentation_begin();
/* Panic on events from a high stack level */
if (regs->fred_cs.sl > 0) {
pr_emerg("PANIC: invalid or fatal FRED event; event type %u "
"vector %u error 0x%lx aux 0x%lx at %04x:%016lx\n",
regs->fred_ss.type, regs->fred_ss.vector, error_code,
fred_event_data(regs), regs->cs, regs->ip);
die("invalid or fatal FRED event", regs, error_code);
panic("invalid or fatal FRED event");
} else {
unsigned long flags = oops_begin();
int sig = SIGKILL;
pr_alert("BUG: invalid or fatal FRED event; event type %u "
"vector %u error 0x%lx aux 0x%lx at %04x:%016lx\n",
regs->fred_ss.type, regs->fred_ss.vector, error_code,
fred_event_data(regs), regs->cs, regs->ip);
if (__die("Invalid or fatal FRED event", regs, error_code))
sig = 0;
oops_end(flags, regs, sig);
}
instrumentation_end();
irqentry_nmi_exit(regs, irq_state);
}
static noinstr void fred_intx(struct pt_regs *regs)
{
switch (regs->fred_ss.vector) {
/* Opcode 0xcd, 0x3, NOT INT3 (opcode 0xcc) */
case X86_TRAP_BP:
return exc_int3(regs);
/* Opcode 0xcd, 0x4, NOT INTO (opcode 0xce) */
case X86_TRAP_OF:
return exc_overflow(regs);
#ifdef CONFIG_IA32_EMULATION
/* INT80 */
case IA32_SYSCALL_VECTOR:
if (ia32_enabled())
return fred_int80_emulation(regs);
fallthrough;
#endif
default:
return exc_general_protection(regs, 0);
}
}
static __always_inline void fred_other(struct pt_regs *regs)
{
/* The compiler can fold these conditions into a single test */
if (likely(regs->fred_ss.vector == FRED_SYSCALL && regs->fred_ss.lm)) {
regs->orig_ax = regs->ax;
regs->ax = -ENOSYS;
do_syscall_64(regs, regs->orig_ax);
return;
} else if (ia32_enabled() &&
likely(regs->fred_ss.vector == FRED_SYSENTER && !regs->fred_ss.lm)) {
regs->orig_ax = regs->ax;
regs->ax = -ENOSYS;
do_fast_syscall_32(regs);
return;
} else {
exc_invalid_op(regs);
return;
}
}
#define SYSVEC(_vector, _function) [_vector - FIRST_SYSTEM_VECTOR] = fred_sysvec_##_function
static idtentry_t sysvec_table[NR_SYSTEM_VECTORS] __ro_after_init = {
SYSVEC(ERROR_APIC_VECTOR, error_interrupt),
SYSVEC(SPURIOUS_APIC_VECTOR, spurious_apic_interrupt),
SYSVEC(LOCAL_TIMER_VECTOR, apic_timer_interrupt),
SYSVEC(X86_PLATFORM_IPI_VECTOR, x86_platform_ipi),
SYSVEC(RESCHEDULE_VECTOR, reschedule_ipi),
SYSVEC(CALL_FUNCTION_SINGLE_VECTOR, call_function_single),
SYSVEC(CALL_FUNCTION_VECTOR, call_function),
SYSVEC(REBOOT_VECTOR, reboot),
SYSVEC(THRESHOLD_APIC_VECTOR, threshold),
SYSVEC(DEFERRED_ERROR_VECTOR, deferred_error),
SYSVEC(THERMAL_APIC_VECTOR, thermal),
SYSVEC(IRQ_WORK_VECTOR, irq_work),
SYSVEC(POSTED_INTR_VECTOR, kvm_posted_intr_ipi),
SYSVEC(POSTED_INTR_WAKEUP_VECTOR, kvm_posted_intr_wakeup_ipi),
SYSVEC(POSTED_INTR_NESTED_VECTOR, kvm_posted_intr_nested_ipi),
SYSVEC(POSTED_MSI_NOTIFICATION_VECTOR, posted_msi_notification),
};
static bool fred_setup_done __initdata;
void __init fred_install_sysvec(unsigned int sysvec, idtentry_t handler)
{
if (WARN_ON_ONCE(sysvec < FIRST_SYSTEM_VECTOR))
return;
if (WARN_ON_ONCE(fred_setup_done))
return;
if (!WARN_ON_ONCE(sysvec_table[sysvec - FIRST_SYSTEM_VECTOR]))
sysvec_table[sysvec - FIRST_SYSTEM_VECTOR] = handler;
}
static noinstr void fred_handle_spurious_interrupt(struct pt_regs *regs)
{
spurious_interrupt(regs, regs->fred_ss.vector);
}
void __init fred_complete_exception_setup(void)
{
unsigned int vector;
for (vector = 0; vector < FIRST_EXTERNAL_VECTOR; vector++)
set_bit(vector, system_vectors);
for (vector = 0; vector < NR_SYSTEM_VECTORS; vector++) {
if (sysvec_table[vector])
set_bit(vector + FIRST_SYSTEM_VECTOR, system_vectors);
else
sysvec_table[vector] = fred_handle_spurious_interrupt;
}
fred_setup_done = true;
}
static noinstr void fred_extint(struct pt_regs *regs)
{
unsigned int vector = regs->fred_ss.vector;
unsigned int index = array_index_nospec(vector - FIRST_SYSTEM_VECTOR,
NR_SYSTEM_VECTORS);
if (WARN_ON_ONCE(vector < FIRST_EXTERNAL_VECTOR))
return;
if (likely(vector >= FIRST_SYSTEM_VECTOR)) {
irqentry_state_t state = irqentry_enter(regs);
instrumentation_begin();
sysvec_table[index](regs);
instrumentation_end();
irqentry_exit(regs, state);
} else {
common_interrupt(regs, vector);
}
}
static noinstr void fred_hwexc(struct pt_regs *regs, unsigned long error_code)
{
/* Optimize for #PF. That's the only exception which matters performance wise */
if (likely(regs->fred_ss.vector == X86_TRAP_PF))
return exc_page_fault(regs, error_code);
switch (regs->fred_ss.vector) {
case X86_TRAP_DE: return exc_divide_error(regs);
case X86_TRAP_DB: return fred_exc_debug(regs);
case X86_TRAP_BR: return exc_bounds(regs);
case X86_TRAP_UD: return exc_invalid_op(regs);
case X86_TRAP_NM: return exc_device_not_available(regs);
case X86_TRAP_DF: return exc_double_fault(regs, error_code);
case X86_TRAP_TS: return exc_invalid_tss(regs, error_code);
case X86_TRAP_NP: return exc_segment_not_present(regs, error_code);
case X86_TRAP_SS: return exc_stack_segment(regs, error_code);
case X86_TRAP_GP: return exc_general_protection(regs, error_code);
case X86_TRAP_MF: return exc_coprocessor_error(regs);
case X86_TRAP_AC: return exc_alignment_check(regs, error_code);
case X86_TRAP_XF: return exc_simd_coprocessor_error(regs);
#ifdef CONFIG_X86_MCE
case X86_TRAP_MC: return fred_exc_machine_check(regs);
#endif
#ifdef CONFIG_INTEL_TDX_GUEST
case X86_TRAP_VE: return exc_virtualization_exception(regs);
#endif
#ifdef CONFIG_X86_CET
case X86_TRAP_CP: return exc_control_protection(regs, error_code);
#endif
default: return fred_bad_type(regs, error_code);
}
}
static noinstr void fred_swexc(struct pt_regs *regs, unsigned long error_code)
{
switch (regs->fred_ss.vector) {
case X86_TRAP_BP: return exc_int3(regs);
case X86_TRAP_OF: return exc_overflow(regs);
default: return fred_bad_type(regs, error_code);
}
}
__visible noinstr void fred_entry_from_user(struct pt_regs *regs)
{
unsigned long error_code = regs->orig_ax;
/* Invalidate orig_ax so that syscall_get_nr() works correctly */
regs->orig_ax = -1;
switch (regs->fred_ss.type) {
case EVENT_TYPE_EXTINT:
return fred_extint(regs);
case EVENT_TYPE_NMI:
if (likely(regs->fred_ss.vector == X86_TRAP_NMI))
return fred_exc_nmi(regs);
break;
case EVENT_TYPE_HWEXC:
return fred_hwexc(regs, error_code);
case EVENT_TYPE_SWINT:
return fred_intx(regs);
case EVENT_TYPE_PRIV_SWEXC:
if (likely(regs->fred_ss.vector == X86_TRAP_DB))
return fred_exc_debug(regs);
break;
case EVENT_TYPE_SWEXC:
return fred_swexc(regs, error_code);
case EVENT_TYPE_OTHER:
return fred_other(regs);
default: break;
}
return fred_bad_type(regs, error_code);
}
__visible noinstr void fred_entry_from_kernel(struct pt_regs *regs)
{
unsigned long error_code = regs->orig_ax;
/* Invalidate orig_ax so that syscall_get_nr() works correctly */
regs->orig_ax = -1;
switch (regs->fred_ss.type) {
case EVENT_TYPE_EXTINT:
return fred_extint(regs);
case EVENT_TYPE_NMI:
if (likely(regs->fred_ss.vector == X86_TRAP_NMI))
return fred_exc_nmi(regs);
break;
case EVENT_TYPE_HWEXC:
return fred_hwexc(regs, error_code);
case EVENT_TYPE_PRIV_SWEXC:
if (likely(regs->fred_ss.vector == X86_TRAP_DB))
return fred_exc_debug(regs);
break;
case EVENT_TYPE_SWEXC:
return fred_swexc(regs, error_code);
default: break;
}
return fred_bad_type(regs, error_code);
}
#if IS_ENABLED(CONFIG_KVM_INTEL)
__visible noinstr void __fred_entry_from_kvm(struct pt_regs *regs)
{
switch (regs->fred_ss.type) {
case EVENT_TYPE_EXTINT:
return fred_extint(regs);
case EVENT_TYPE_NMI:
return fred_exc_nmi(regs);
default:
WARN_ON_ONCE(1);
}
}
#endif
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