[PATCH v2 0/5] x86: Cleanups around slow_down_io()

[PATCH v2 0/5] x86: Cleanups around slow_down_io()

[Juergen Gross]

While looking at paravirt cleanups I stumbled over slow_down_io() and
the related REALLY_SLOW_IO define.

Do several cleanups, resulting in a deletion of REALLY_SLOW_IO and the
io_delay() paravirt function hook.

Patch 4 is removing the config options for selecting the default delay
mechanism and sets the default to "no delay". This is in preparation of
removing the io_delay() functionality completely, as suggested by Ingo
Molnar.

Patch 5 is adding an additional config option allowing to avoid
building io_delay.c (default is still to build it).

Changes in V2:
- patches 2 and 3 of V1 have been applied
- new patches 4 and 5

Juergen Gross (5):
  x86/paravirt: Replace io_delay() hook with a bool
  block/floppy: Don't use REALLY_SLOW_IO for delays
  x86/io: Remove REALLY_SLOW_IO handling
  x86/io_delay: Switch io_delay() default mechanism to "none"
  x86/io_delay: Add config option for controlling build of io_delay.

 arch/x86/Kconfig                      |  8 +++
 arch/x86/Kconfig.debug                | 30 ----------
 arch/x86/include/asm/floppy.h         | 31 ++++++++--
 arch/x86/include/asm/io.h             | 17 +++---
 arch/x86/include/asm/paravirt.h       | 11 +---
 arch/x86/include/asm/paravirt_types.h |  3 +-
 arch/x86/kernel/Makefile              |  3 +-
 arch/x86/kernel/cpu/vmware.c          |  2 +-
 arch/x86/kernel/io_delay.c            | 81 +--------------------------
 arch/x86/kernel/kvm.c                 |  8 +--
 arch/x86/kernel/paravirt.c            |  3 +-
 arch/x86/kernel/setup.c               |  4 +-
 arch/x86/xen/enlighten_pv.c           |  6 +-
 drivers/block/floppy.c                |  2 -
 14 files changed, 55 insertions(+), 154 deletions(-)

-- 
2.51.0

[PATCH v2 1/5] x86/paravirt: Replace io_delay() hook with a bool

[Juergen Gross]

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.

This enables to replace the hook with a bool indicating whether
native_io_delay() should be called.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/include/asm/io.h             |  7 +++++--
 arch/x86/include/asm/paravirt.h       | 11 +----------
 arch/x86/include/asm/paravirt_types.h |  3 +--
 arch/x86/kernel/cpu/vmware.c          |  2 +-
 arch/x86/kernel/kvm.c                 |  8 +-------
 arch/x86/kernel/paravirt.c            |  3 +--
 arch/x86/xen/enlighten_pv.c           |  6 +-----
 7 files changed, 11 insertions(+), 29 deletions(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index ca309a3227c7..0448575569b9 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -245,9 +245,14 @@ extern void io_delay_init(void);
 #if defined(CONFIG_PARAVIRT)
 #include <asm/paravirt.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();
@@ -256,8 +261,6 @@ static inline void slow_down_io(void)
 #endif
 }
 
-#endif
-
 #define BUILDIO(bwl, type)						\
 static inline void out##bwl##_p(type value, u16 port)			\
 {									\
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index b5e59a7ba0d0..0ab798d234cc 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -53,16 +53,7 @@ static inline u64 paravirt_steal_clock(int cpu)
 void __init paravirt_set_cap(void);
 #endif
 
-/* The paravirtualized I/O functions */
-static inline void slow_down_io(void)
-{
-	PVOP_VCALL0(cpu.io_delay);
-#ifdef REALLY_SLOW_IO
-	PVOP_VCALL0(cpu.io_delay);
-	PVOP_VCALL0(cpu.io_delay);
-	PVOP_VCALL0(cpu.io_delay);
-#endif
-}
+#define call_io_delay() pv_info.io_delay
 
 void native_flush_tlb_local(void);
 void native_flush_tlb_global(void);
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 3502939415ad..b4c15856eab5 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -36,6 +36,7 @@ struct pv_info {
 #ifdef CONFIG_PARAVIRT_XXL
 	u16 extra_user_64bit_cs;  /* __USER_CS if none */
 #endif
+	bool io_delay;
 
 	const char *name;
 };
@@ -51,8 +52,6 @@ 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);
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index cb3f900c46fc..47db25d63c8d 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -338,7 +338,7 @@ 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;
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index df78ddee0abb..24e403cdce69 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -74,12 +74,6 @@ 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)
@@ -313,7 +307,7 @@ 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;
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index ab3e172dcc69..8ee952e7e7d4 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -113,6 +113,7 @@ struct pv_info pv_info = {
 #ifdef CONFIG_PARAVIRT_XXL
 	.extra_user_64bit_cs = __USER_CS,
 #endif
+	.io_delay = true,
 };
 
 /* 64-bit pagetable entries */
@@ -120,8 +121,6 @@ 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,
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 4806cc28d7ca..a43b525f25cd 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1046,10 +1046,6 @@ 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)
@@ -1209,6 +1205,7 @@ 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",
 };
 
@@ -1253,7 +1250,6 @@ static const typeof(pv_ops) xen_cpu_ops __initconst = {
 		.invalidate_io_bitmap = xen_invalidate_io_bitmap,
 		.update_io_bitmap = xen_update_io_bitmap,
 #endif
-		.io_delay = xen_io_delay,
 
 		.start_context_switch = xen_start_context_switch,
 		.end_context_switch = xen_end_context_switch,
-- 
2.51.0

[PATCH v2 2/5] block/floppy: Don't use REALLY_SLOW_IO for delays

[Juergen Gross]

Instead of defining REALLY_SLOW_IO before including io.h, add the
required additional calls of native_io_delay() to the related functions
in arch/x86/include/asm/floppy.h.

This will remove the last place where REALLY_SLOW_IO is being defined.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/include/asm/floppy.h | 27 ++++++++++++++++++++++-----
 drivers/block/floppy.c        |  2 --
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/floppy.h b/arch/x86/include/asm/floppy.h
index e7a244051c62..8d1e86687b98 100644
--- a/arch/x86/include/asm/floppy.h
+++ b/arch/x86/include/asm/floppy.h
@@ -29,9 +29,6 @@
 #define CSW fd_routine[can_use_virtual_dma & 1]
 
 
-#define fd_inb(base, reg)		inb_p((base) + (reg))
-#define fd_outb(value, base, reg)	outb_p(value, (base) + (reg))
-
 #define fd_request_dma()	CSW._request_dma(FLOPPY_DMA, "floppy")
 #define fd_free_dma()		CSW._free_dma(FLOPPY_DMA)
 #define fd_enable_irq()		enable_irq(FLOPPY_IRQ)
@@ -49,6 +46,26 @@ static char *virtual_dma_addr;
 static int virtual_dma_mode;
 static int doing_pdma;
 
+static inline u8 fd_inb(u16 base, u16 reg)
+{
+	u8 ret = inb_p(base + reg);
+
+	native_io_delay();
+	native_io_delay();
+	native_io_delay();
+
+	return ret;
+}
+
+static inline void fd_outb(u8 value, u16 base, u16 reg)
+{
+	outb_p(value, base + reg);
+
+	native_io_delay();
+	native_io_delay();
+	native_io_delay();
+}
+
 static irqreturn_t floppy_hardint(int irq, void *dev_id)
 {
 	unsigned char st;
@@ -79,9 +96,9 @@ static irqreturn_t floppy_hardint(int irq, void *dev_id)
 			if (st != (STATUS_DMA | STATUS_READY))
 				break;
 			if (virtual_dma_mode)
-				outb_p(*lptr, virtual_dma_port + FD_DATA);
+				fd_outb(*lptr, virtual_dma_port, FD_DATA);
 			else
-				*lptr = inb_p(virtual_dma_port + FD_DATA);
+				*lptr = fd_inb(virtual_dma_port, FD_DATA);
 		}
 		virtual_dma_count = lcount;
 		virtual_dma_addr = lptr;
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index c28786e0fe1c..4422bc57a4f2 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -145,8 +145,6 @@
  * Better audit of register_blkdev.
  */
 
-#define REALLY_SLOW_IO
-
 #define DEBUGT 2
 
 #define DPRINT(format, args...) \
-- 
2.51.0

[PATCH v2 3/5] x86/io: Remove REALLY_SLOW_IO handling

[Juergen Gross]

As there is no user of REALLY_SLOW_IO left, remove the related handling
from arch/x86/include/asm/io.h.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/include/asm/io.h | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 0448575569b9..c4ddaaa1b81c 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -254,11 +254,6 @@ static inline void slow_down_io(void)
 		return;
 
 	native_io_delay();
-#ifdef REALLY_SLOW_IO
-	native_io_delay();
-	native_io_delay();
-	native_io_delay();
-#endif
 }
 
 #define BUILDIO(bwl, type)						\
-- 
2.51.0

[PATCH v2 4/5] x86/io_delay: Switch io_delay() default mechanism to "none"

[Juergen Gross]

The habit to delay some port operations via io_delay() is probably a
no longer needed relict from i386 times.

Switch the default to no longer do delays for port operations. In case
this is breaking some still supported hardware, the default can still
be overwritten via boot parameter.

Remove the Kconfig options to select the default io_delay() mechanism.
This makes io_delay_init() a nop, so it can be removed together with
dmi_io_delay_0xed_port() and the associatedr
io_delay_0xed_port_dmi_table().

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- new patch (kind of suggested by Ingo Molnar)
---
 arch/x86/Kconfig.debug     | 30 --------------
 arch/x86/include/asm/io.h  |  1 -
 arch/x86/kernel/io_delay.c | 81 +-------------------------------------
 arch/x86/kernel/setup.c    |  2 -
 4 files changed, 1 insertion(+), 113 deletions(-)

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index c95c3aaadf97..56888156a64b 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -120,36 +120,6 @@ config X86_DECODER_SELFTEST
 	  decoder code.
 	  If unsure, say "N".
 
-choice
-	prompt "IO delay type"
-	default IO_DELAY_0X80
-
-config IO_DELAY_0X80
-	bool "port 0x80 based port-IO delay [recommended]"
-	help
-	  This is the traditional Linux IO delay used for in/out_p.
-	  It is the most tested hence safest selection here.
-
-config IO_DELAY_0XED
-	bool "port 0xed based port-IO delay"
-	help
-	  Use port 0xed as the IO delay. This frees up port 0x80 which is
-	  often used as a hardware-debug port.
-
-config IO_DELAY_UDELAY
-	bool "udelay based port-IO delay"
-	help
-	  Use udelay(2) as the IO delay method. This provides the delay
-	  while not having any side-effect on the IO port space.
-
-config IO_DELAY_NONE
-	bool "no port-IO delay"
-	help
-	  No port-IO delay. Will break on old boxes that require port-IO
-	  delay for certain operations. Should work on most new machines.
-
-endchoice
-
 config DEBUG_BOOT_PARAMS
 	bool "Debug boot parameters"
 	depends on DEBUG_KERNEL
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index c4ddaaa1b81c..9c4178f2d094 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -240,7 +240,6 @@ static inline void __iowrite32_copy(void __iomem *to, const void *from,
 extern void native_io_delay(void);
 
 extern int io_delay_type;
-extern void io_delay_init(void);
 
 #if defined(CONFIG_PARAVIRT)
 #include <asm/paravirt.h>
diff --git a/arch/x86/kernel/io_delay.c b/arch/x86/kernel/io_delay.c
index fdb6506ceaaa..458e2fd9279b 100644
--- a/arch/x86/kernel/io_delay.c
+++ b/arch/x86/kernel/io_delay.c
@@ -9,8 +9,6 @@
 #include <linux/kernel.h>
 #include <linux/export.h>
 #include <linux/delay.h>
-#include <linux/init.h>
-#include <linux/dmi.h>
 #include <linux/io.h>
 
 #define IO_DELAY_TYPE_0X80	0
@@ -18,19 +16,7 @@
 #define IO_DELAY_TYPE_UDELAY	2
 #define IO_DELAY_TYPE_NONE	3
 
-#if defined(CONFIG_IO_DELAY_0X80)
-#define DEFAULT_IO_DELAY_TYPE	IO_DELAY_TYPE_0X80
-#elif defined(CONFIG_IO_DELAY_0XED)
-#define DEFAULT_IO_DELAY_TYPE	IO_DELAY_TYPE_0XED
-#elif defined(CONFIG_IO_DELAY_UDELAY)
-#define DEFAULT_IO_DELAY_TYPE	IO_DELAY_TYPE_UDELAY
-#elif defined(CONFIG_IO_DELAY_NONE)
-#define DEFAULT_IO_DELAY_TYPE	IO_DELAY_TYPE_NONE
-#endif
-
-int io_delay_type __read_mostly = DEFAULT_IO_DELAY_TYPE;
-
-static int __initdata io_delay_override;
+int io_delay_type __read_mostly = IO_DELAY_TYPE_NONE;
 
 /*
  * Paravirt wants native_io_delay to be a constant.
@@ -61,70 +47,6 @@ void native_io_delay(void)
 }
 EXPORT_SYMBOL(native_io_delay);
 
-static int __init dmi_io_delay_0xed_port(const struct dmi_system_id *id)
-{
-	if (io_delay_type == IO_DELAY_TYPE_0X80) {
-		pr_notice("%s: using 0xed I/O delay port\n", id->ident);
-		io_delay_type = IO_DELAY_TYPE_0XED;
-	}
-
-	return 0;
-}
-
-/*
- * Quirk table for systems that misbehave (lock up, etc.) if port
- * 0x80 is used:
- */
-static const struct dmi_system_id io_delay_0xed_port_dmi_table[] __initconst = {
-	{
-		.callback	= dmi_io_delay_0xed_port,
-		.ident		= "Compaq Presario V6000",
-		.matches	= {
-			DMI_MATCH(DMI_BOARD_VENDOR,	"Quanta"),
-			DMI_MATCH(DMI_BOARD_NAME,	"30B7")
-		}
-	},
-	{
-		.callback	= dmi_io_delay_0xed_port,
-		.ident		= "HP Pavilion dv9000z",
-		.matches	= {
-			DMI_MATCH(DMI_BOARD_VENDOR,	"Quanta"),
-			DMI_MATCH(DMI_BOARD_NAME,	"30B9")
-		}
-	},
-	{
-		.callback	= dmi_io_delay_0xed_port,
-		.ident		= "HP Pavilion dv6000",
-		.matches	= {
-			DMI_MATCH(DMI_BOARD_VENDOR,	"Quanta"),
-			DMI_MATCH(DMI_BOARD_NAME,	"30B8")
-		}
-	},
-	{
-		.callback	= dmi_io_delay_0xed_port,
-		.ident		= "HP Pavilion tx1000",
-		.matches	= {
-			DMI_MATCH(DMI_BOARD_VENDOR,	"Quanta"),
-			DMI_MATCH(DMI_BOARD_NAME,	"30BF")
-		}
-	},
-	{
-		.callback	= dmi_io_delay_0xed_port,
-		.ident		= "Presario F700",
-		.matches	= {
-			DMI_MATCH(DMI_BOARD_VENDOR,	"Quanta"),
-			DMI_MATCH(DMI_BOARD_NAME,	"30D3")
-		}
-	},
-	{ }
-};
-
-void __init io_delay_init(void)
-{
-	if (!io_delay_override)
-		dmi_check_system(io_delay_0xed_port_dmi_table);
-}
-
 static int __init io_delay_param(char *s)
 {
 	if (!s)
@@ -141,7 +63,6 @@ static int __init io_delay_param(char *s)
 	else
 		return -EINVAL;
 
-	io_delay_override = 1;
 	return 0;
 }
 
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 1b2edd07a3e1..8ef29c1ebb8d 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1176,8 +1176,6 @@ void __init setup_arch(char **cmdline_p)
 
 	vsmp_init();
 
-	io_delay_init();
-
 	early_platform_quirks();
 
 	/* Some platforms need the APIC registered for NUMA configuration */
-- 
2.51.0

[PATCH v2 5/5] x86/io_delay: Add config option for controlling build of io_delay.

[Juergen Gross]

Prepare phasing out support of io_delay() by adding a config option
(default on for now) controlling the build of io_delay.c.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- new patch (kind of suggested by Ingo Molnar)
---
 arch/x86/Kconfig              | 8 ++++++++
 arch/x86/include/asm/floppy.h | 4 ++++
 arch/x86/include/asm/io.h     | 6 ++++++
 arch/x86/kernel/Makefile      | 3 ++-
 arch/x86/kernel/setup.c       | 2 ++
 5 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 80527299f859..ae6da2bd6e44 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -3175,6 +3175,14 @@ config HAVE_ATOMIC_IOMAP
 	def_bool y
 	depends on X86_32
 
+config IO_DELAY
+	bool "Support delay of I/O-port activities"
+	default y
+	help
+	  Include code allowing to delay I/O-port activities. This might be
+	  needed on some rather old hardware. The delay mechanism will still
+	  require to be selected via the "io_delay" boot parameter.
+
 source "arch/x86/kvm/Kconfig"
 
 source "arch/x86/Kconfig.cpufeatures"
diff --git a/arch/x86/include/asm/floppy.h b/arch/x86/include/asm/floppy.h
index 8d1e86687b98..d7df95255761 100644
--- a/arch/x86/include/asm/floppy.h
+++ b/arch/x86/include/asm/floppy.h
@@ -50,9 +50,11 @@ static inline u8 fd_inb(u16 base, u16 reg)
 {
 	u8 ret = inb_p(base + reg);
 
+#ifdef CONFIG_IO_DELAY
 	native_io_delay();
 	native_io_delay();
 	native_io_delay();
+#endif
 
 	return ret;
 }
@@ -61,9 +63,11 @@ static inline void fd_outb(u8 value, u16 base, u16 reg)
 {
 	outb_p(value, base + reg);
 
+#ifdef CONFIG_IO_DELAY
 	native_io_delay();
 	native_io_delay();
 	native_io_delay();
+#endif
 }
 
 static irqreturn_t floppy_hardint(int irq, void *dev_id)
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 9c4178f2d094..c5d19665b746 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -237,6 +237,7 @@ static inline void __iowrite32_copy(void __iomem *to, const void *from,
 
 #endif /* __KERNEL__ */
 
+#ifdef CONFIG_IO_DELAY
 extern void native_io_delay(void);
 
 extern int io_delay_type;
@@ -254,6 +255,11 @@ static inline void slow_down_io(void)
 
 	native_io_delay();
 }
+#else
+static inline void slow_down_io(void)
+{
+}
+#endif
 
 #define BUILDIO(bwl, type)						\
 static inline void out##bwl##_p(type value, u16 port)			\
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index bc184dd38d99..f2bb6664b7ca 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -66,11 +66,12 @@ obj-$(CONFIG_X86_32)	+= sys_ia32.o
 obj-$(CONFIG_IA32_EMULATION)	+= sys_ia32.o signal_32.o
 obj-$(CONFIG_X86_64)	+= sys_x86_64.o
 obj-$(CONFIG_X86_ESPFIX64)	+= espfix_64.o
+obj-$(CONFIG_IO_DELAY)	+= io_delay.o
 obj-$(CONFIG_SYSFS)	+= ksysfs.o
 obj-y			+= bootflag.o e820.o
 obj-y			+= pci-dma.o quirks.o kdebugfs.o
 obj-y			+= alternative.o i8253.o hw_breakpoint.o
-obj-y			+= tsc.o tsc_msr.o io_delay.o rtc.o
+obj-y			+= tsc.o tsc_msr.o rtc.o
 obj-y			+= resource.o
 obj-y			+= irqflags.o
 obj-y			+= static_call.o
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 8ef29c1ebb8d..a3fa38a23807 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -183,6 +183,7 @@ static const struct ctl_table x86_sysctl_table[] = {
 		.mode		= 0444,
 		.proc_handler	= proc_dointvec,
 	},
+#ifdef CONFIG_IO_DELAY
 	{
 		.procname	= "io_delay_type",
 		.data		= &io_delay_type,
@@ -190,6 +191,7 @@ static const struct ctl_table x86_sysctl_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+#endif
 #if defined(CONFIG_ACPI_SLEEP)
 	{
 		.procname	= "acpi_video_flags",
-- 
2.51.0

Re: [PATCH v2 0/5] x86: Cleanups around slow_down_io()

[Juergen Gross]

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Gentle ping.

On 16.12.25 14:41, Juergen Gross wrote:
> While looking at paravirt cleanups I stumbled over slow_down_io() and
> the related REALLY_SLOW_IO define.
> 
> Do several cleanups, resulting in a deletion of REALLY_SLOW_IO and the
> io_delay() paravirt function hook.
> 
> Patch 4 is removing the config options for selecting the default delay
> mechanism and sets the default to "no delay". This is in preparation of
> removing the io_delay() functionality completely, as suggested by Ingo
> Molnar.
> 
> Patch 5 is adding an additional config option allowing to avoid
> building io_delay.c (default is still to build it).
> 
> Changes in V2:
> - patches 2 and 3 of V1 have been applied
> - new patches 4 and 5
> 
> Juergen Gross (5):
>    x86/paravirt: Replace io_delay() hook with a bool
>    block/floppy: Don't use REALLY_SLOW_IO for delays
>    x86/io: Remove REALLY_SLOW_IO handling
>    x86/io_delay: Switch io_delay() default mechanism to "none"
>    x86/io_delay: Add config option for controlling build of io_delay.
> 
>   arch/x86/Kconfig                      |  8 +++
>   arch/x86/Kconfig.debug                | 30 ----------
>   arch/x86/include/asm/floppy.h         | 31 ++++++++--
>   arch/x86/include/asm/io.h             | 17 +++---
>   arch/x86/include/asm/paravirt.h       | 11 +---
>   arch/x86/include/asm/paravirt_types.h |  3 +-
>   arch/x86/kernel/Makefile              |  3 +-
>   arch/x86/kernel/cpu/vmware.c          |  2 +-
>   arch/x86/kernel/io_delay.c            | 81 +--------------------------
>   arch/x86/kernel/kvm.c                 |  8 +--
>   arch/x86/kernel/paravirt.c            |  3 +-
>   arch/x86/kernel/setup.c               |  4 +-
>   arch/x86/xen/enlighten_pv.c           |  6 +-
>   drivers/block/floppy.c                |  2 -
>   14 files changed, 55 insertions(+), 154 deletions(-)
> 


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