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x86/paravirt: Replace io_delay() hook with a bool

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The io_delay() paravirt hook is in no way performance critical and all users
setting it to a different function than native_io_delay() are using an empty
function as replacement.

Allow replacing the hook with a bool indicating whether native_io_delay()
should be called.

  [ bp: Massage commit message. ]

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20260119182632.596369-3-jgross@suse.com
This commit is contained in:
Juergen Gross
2026-01-19 19:26:28 +01:00
committed by Ingo Molnar
parent 36c1eb9531
commit 9eece49856
8 changed files with 16 additions and 31 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
arch/x86/include/asm/io.h
View File

@@ -242,11 +242,16 @@ extern int io_delay_type;
extern void io_delay_init(void);
#if defined(CONFIG_PARAVIRT)
#include <asm/paravirt.h>
#include <asm/paravirt-base.h>
#else
#define call_io_delay() true
#endif
static inline void slow_down_io(void)
{
if (!call_io_delay())
return;
native_io_delay();
#ifdef REALLY_SLOW_IO
native_io_delay();
@@ -255,8 +260,6 @@ static inline void slow_down_io(void)
#endif
}
#endif
#define BUILDIO(bwl, type) \
static inline void out##bwl##_p(type value, u16 port) \
{ \

6
arch/x86/include/asm/paravirt-base.h
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@@ -15,6 +15,8 @@ struct pv_info {
#ifdef CONFIG_PARAVIRT_XXL
u16 extra_user_64bit_cs; /* __USER_CS if none */
#endif
bool io_delay;
const char *name;
};
@@ -26,6 +28,10 @@ u64 _paravirt_ident_64(u64);
#endif
#define paravirt_nop ((void *)nop_func)
#ifdef CONFIG_PARAVIRT
#define call_io_delay() pv_info.io_delay
#endif
#ifdef CONFIG_PARAVIRT_SPINLOCKS
void paravirt_set_cap(void);
#else

11
arch/x86/include/asm/paravirt.h
View File

@@ -19,17 +19,6 @@
#include <linux/cpumask.h>
#include <asm/frame.h>
/* The paravirtualized I/O functions */
static inline void slow_down_io(void)
{
PVOP_VCALL0(pv_ops, cpu.io_delay);
#ifdef REALLY_SLOW_IO
PVOP_VCALL0(pv_ops, cpu.io_delay);
PVOP_VCALL0(pv_ops, cpu.io_delay);
PVOP_VCALL0(pv_ops, cpu.io_delay);
#endif
}
void native_flush_tlb_local(void);
void native_flush_tlb_global(void);
void native_flush_tlb_one_user(unsigned long addr);

2
arch/x86/include/asm/paravirt_types.h
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@@ -30,8 +30,6 @@ struct pv_lazy_ops {
struct pv_cpu_ops {
/* hooks for various privileged instructions */
void (*io_delay)(void);
#ifdef CONFIG_PARAVIRT_XXL
unsigned long (*get_debugreg)(int regno);
void (*set_debugreg)(int regno, unsigned long value);

2
arch/x86/kernel/cpu/vmware.c
View File

@@ -339,7 +339,7 @@ arch_initcall(activate_jump_labels);
static void __init vmware_paravirt_ops_setup(void)
{
pv_info.name = "VMware hypervisor";
pv_ops.cpu.io_delay = paravirt_nop;
pv_info.io_delay = false;
if (vmware_tsc_khz == 0)
return;

8
arch/x86/kernel/kvm.c
View File

@@ -75,12 +75,6 @@ DEFINE_PER_CPU_DECRYPTED(struct kvm_steal_time, steal_time) __aligned(64) __visi
static int has_steal_clock = 0;
static int has_guest_poll = 0;
/*
* No need for any "IO delay" on KVM
*/
static void kvm_io_delay(void)
{
}
#define KVM_TASK_SLEEP_HASHBITS 8
#define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)
@@ -327,7 +321,7 @@ static void __init paravirt_ops_setup(void)
pv_info.name = "KVM";
if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
pv_ops.cpu.io_delay = kvm_io_delay;
pv_info.io_delay = false;
#ifdef CONFIG_X86_IO_APIC
no_timer_check = 1;

3
arch/x86/kernel/paravirt.c
View File

@@ -94,6 +94,7 @@ struct pv_info pv_info = {
#ifdef CONFIG_PARAVIRT_XXL
.extra_user_64bit_cs = __USER_CS,
#endif
.io_delay = true,
};
/* 64-bit pagetable entries */
@@ -101,8 +102,6 @@ struct pv_info pv_info = {
struct paravirt_patch_template pv_ops = {
/* Cpu ops. */
.cpu.io_delay = native_io_delay,
#ifdef CONFIG_PARAVIRT_XXL
.cpu.cpuid = native_cpuid,
.cpu.get_debugreg = pv_native_get_debugreg,

6
arch/x86/xen/enlighten_pv.c
View File

@@ -1045,10 +1045,6 @@ static void xen_update_io_bitmap(void)
}
#endif
static void xen_io_delay(void)
{
}
static DEFINE_PER_CPU(unsigned long, xen_cr0_value);
static unsigned long xen_read_cr0(void)
@@ -1208,6 +1204,7 @@ void __init xen_setup_vcpu_info_placement(void)
static const struct pv_info xen_info __initconst = {
.extra_user_64bit_cs = FLAT_USER_CS64,
.io_delay = false,
.name = "Xen",
};
@@ -1391,7 +1388,6 @@ asmlinkage __visible void __init xen_start_kernel(struct start_info *si)
pv_ops.cpu.invalidate_io_bitmap = xen_invalidate_io_bitmap;
pv_ops.cpu.update_io_bitmap = xen_update_io_bitmap;
#endif
pv_ops.cpu.io_delay = xen_io_delay;
pv_ops.cpu.start_context_switch = xen_start_context_switch;
pv_ops.cpu.end_context_switch = xen_end_context_switch;