Re: [patch V2 50/58] x86/apic: Provide common init infrastructure

[Juergen Gross <jgross@suse.com>]

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On 24.07.23 15:35, Thomas Gleixner wrote:
> In preparation for converting the hotpath APIC callbacks to static keys,
> provide common initialization inforastructure.
> 
> Lift apic_install_drivers() from probe_64.c and convert all places which
> switch the apic instance by storing the pointer to use apic_install_driver()
> as a first step.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>   arch/x86/include/asm/apic.h         |    2 +
>   arch/x86/kernel/apic/Makefile       |    2 -
>   arch/x86/kernel/apic/apic.c         |   31 -----------------------
>   arch/x86/kernel/apic/apic_flat_64.c |    6 ----
>   arch/x86/kernel/apic/bigsmp_32.c    |    6 +---
>   arch/x86/kernel/apic/init.c         |   47 ++++++++++++++++++++++++++++++++++++
>   arch/x86/kernel/apic/probe_32.c     |    5 +--
>   arch/x86/kernel/apic/probe_64.c     |   13 ---------
>   arch/x86/xen/apic.c                 |   10 ++-----
>   9 files changed, 59 insertions(+), 63 deletions(-)
> 
> --- a/arch/x86/include/asm/apic.h
> +++ b/arch/x86/include/asm/apic.h
> @@ -344,6 +344,8 @@ extern int lapic_can_unplug_cpu(void);
>   
>   #ifdef CONFIG_X86_LOCAL_APIC
>   
> +void __init apic_install_driver(struct apic *driver);
> +
>   static inline u32 apic_read(u32 reg)
>   {
>   	return apic->read(reg);
> --- a/arch/x86/kernel/apic/Makefile
> +++ b/arch/x86/kernel/apic/Makefile
> @@ -7,7 +7,7 @@
>   # In particualr, smp_apic_timer_interrupt() is called in random places.
>   KCOV_INSTRUMENT		:= n
>   
> -obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o apic_common.o apic_noop.o ipi.o vector.o
> +obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o apic_common.o apic_noop.o ipi.o vector.o init.o
>   obj-y				+= hw_nmi.o
>   
>   obj-$(CONFIG_X86_IO_APIC)	+= io_apic.o
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -236,8 +236,7 @@ static int modern_apic(void)
>    */
>   static void __init apic_disable(void)
>   {
> -	pr_info("APIC: switched to apic NOOP\n");
> -	apic = &apic_noop;
> +	apic_install_driver(&apic_noop);
>   }
>   
>   void native_apic_icr_write(u32 low, u32 id)
> @@ -2486,34 +2485,6 @@ u32 x86_msi_msg_get_destid(struct msi_ms
>   }
>   EXPORT_SYMBOL_GPL(x86_msi_msg_get_destid);
>   
> -#ifdef CONFIG_X86_64
> -void __init acpi_wake_cpu_handler_update(wakeup_cpu_handler handler)
> -{
> -	struct apic **drv;
> -
> -	for (drv = __apicdrivers; drv < __apicdrivers_end; drv++)
> -		(*drv)->wakeup_secondary_cpu_64 = handler;
> -}
> -#endif
> -
> -/*
> - * Override the generic EOI implementation with an optimized version.
> - * Only called during early boot when only one CPU is active and with
> - * interrupts disabled, so we know this does not race with actual APIC driver
> - * use.
> - */
> -void __init apic_set_eoi_cb(void (*eoi)(void))
> -{
> -	struct apic **drv;
> -
> -	for (drv = __apicdrivers; drv < __apicdrivers_end; drv++) {
> -		/* Should happen once for each apic */
> -		WARN_ON((*drv)->eoi == eoi);
> -		(*drv)->native_eoi = (*drv)->eoi;
> -		(*drv)->eoi = eoi;
> -	}
> -}
> -
>   static void __init apic_bsp_up_setup(void)
>   {
>   #ifdef CONFIG_X86_64
> --- a/arch/x86/kernel/apic/apic_flat_64.c
> +++ b/arch/x86/kernel/apic/apic_flat_64.c
> @@ -143,11 +143,7 @@ static int physflat_acpi_madt_oem_check(
>   
>   static int physflat_probe(void)
>   {
> -	if (apic == &apic_physflat || num_possible_cpus() > 8 ||
> -	    jailhouse_paravirt())
> -		return 1;
> -
> -	return 0;
> +	return apic == &apic_physflat || num_possible_cpus() > 8 || jailhouse_paravirt();
>   }
>   
>   static struct apic apic_physflat __ro_after_init = {
> --- a/arch/x86/kernel/apic/bigsmp_32.c
> +++ b/arch/x86/kernel/apic/bigsmp_32.c
> @@ -119,10 +119,8 @@ bool __init apic_bigsmp_possible(bool cm
>   
>   void __init apic_bigsmp_force(void)
>   {
> -	if (apic != &apic_bigsmp) {
> -		apic = &apic_bigsmp;
> -		pr_info("Overriding APIC driver with bigsmp\n");
> -	}
> +	if (apic != &apic_bigsmp)
> +		apic_install_driver(&apic_bigsmp);
>   }
>   
>   apic_driver(apic_bigsmp);
> --- /dev/null
> +++ b/arch/x86/kernel/apic/init.c
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#define pr_fmt(fmt) "APIC: " fmt
> +
> +#include <asm/apic.h>
> +
> +#include "local.h"
> +
> +void __init apic_install_driver(struct apic *driver)
> +{
> +	if (apic == driver)
> +		return;
> +
> +	apic = driver;
> +
> +	if (IS_ENABLED(CONFIG_X86_X2APIC) && apic->x2apic_set_max_apicid)
> +		apic->max_apic_id = x2apic_max_apicid;
> +
> +	pr_info("Switched APIC routing to: %s\n", driver->name);
> +}
> +
> +#ifdef CONFIG_X86_64
> +void __init acpi_wake_cpu_handler_update(wakeup_cpu_handler handler)
> +{
> +	struct apic **drv;
> +
> +	for (drv = __apicdrivers; drv < __apicdrivers_end; drv++)
> +		(*drv)->wakeup_secondary_cpu_64 = handler;
> +}
> +#endif
> +
> +/*
> + * Override the generic EOI implementation with an optimized version.
> + * Only called during early boot when only one CPU is active and with
> + * interrupts disabled, so we know this does not race with actual APIC driver
> + * use.
> + */
> +void __init apic_set_eoi_cb(void (*eoi)(void))
> +{
> +	struct apic **drv;
> +
> +	for (drv = __apicdrivers; drv < __apicdrivers_end; drv++) {
> +		/* Should happen once for each apic */
> +		WARN_ON((*drv)->eoi == eoi);
> +		(*drv)->native_eoi = (*drv)->eoi;
> +		(*drv)->eoi = eoi;
> +	}
> +}
> --- a/arch/x86/kernel/apic/probe_32.c
> +++ b/arch/x86/kernel/apic/probe_32.c
> @@ -82,7 +82,7 @@ static int __init parse_apic(char *arg)
>   
>   	for (drv = __apicdrivers; drv < __apicdrivers_end; drv++) {
>   		if (!strcmp((*drv)->name, arg)) {
> -			apic = *drv;
> +			apic_install_driver(*drv);
>   			cmdline_apic = 1;
>   			return 0;
>   		}
> @@ -129,7 +129,7 @@ void __init x86_32_probe_apic(void)
>   
>   		for (drv = __apicdrivers; drv < __apicdrivers_end; drv++) {
>   			if ((*drv)->probe()) {
> -				apic = *drv;
> +				apic_install_driver(*drv);
>   				break;
>   			}
>   		}
> @@ -137,5 +137,4 @@ void __init x86_32_probe_apic(void)
>   		if (drv == __apicdrivers_end)
>   			panic("Didn't find an APIC driver");
>   	}
> -	printk(KERN_INFO "Using APIC driver %s\n", apic->name);
>   }
> --- a/arch/x86/kernel/apic/probe_64.c
> +++ b/arch/x86/kernel/apic/probe_64.c
> @@ -13,19 +13,6 @@
>   
>   #include "local.h"
>   
> -static __init void apic_install_driver(struct apic *driver)
> -{
> -	if (apic == driver)
> -		return;
> -
> -	apic = driver;
> -
> -	if (IS_ENABLED(CONFIG_X86_X2APIC) && apic->x2apic_set_max_apicid)
> -		apic->max_apic_id = x2apic_max_apicid;
> -
> -	pr_info("Switched APIC routing to %s:\n", apic->name);
> -}
> -
>   /* Select the appropriate APIC driver */
>   void __init x86_64_probe_apic(void)
>   {
> --- a/arch/x86/xen/apic.c
> +++ b/arch/x86/xen/apic.c
> @@ -160,20 +160,16 @@ static struct apic xen_pv_apic = {
>   
>   static void __init xen_apic_check(void)
>   {
> -	if (apic == &xen_pv_apic)
> -		return;
> -
> -	pr_info("Switched APIC routing from %s to %s.\n", apic->name,
> -		xen_pv_apic.name);
> -	apic = &xen_pv_apic;
> +	apic_install_driver(&xen_pv_apic);
>   }
> +
>   void __init xen_init_apic(void)
>   {
>   	x86_apic_ops.io_apic_read = xen_io_apic_read;
>   	/* On PV guests the APIC CPUID bit is disabled so none of the
>   	 * routines end up executing. */
>   	if (!xen_initial_domain())
> -		apic = &xen_pv_apic;
> +		apic_install_driver(&xen_pv_apic);

This is working, but it produces a WARN() splat when booting as an unprivileged
Xen PV guest from static_call patching (static_call_init() hasn't been called
yet).

The diff below on top is fixing the issue:

diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c
index 1838aefc632f..84f24268670b 100644
--- a/arch/x86/xen/apic.c
+++ b/arch/x86/xen/apic.c
@@ -163,14 +163,18 @@ static void __init xen_apic_check(void)
         apic_install_driver(&xen_pv_apic);
  }

+void __init xen_apic_install(void)
+{
+       /*
+        * On PV guests the APIC CPUID bit is disabled so none of the
+        * routines end up executing.
+        */
+       apic_install_driver(&xen_pv_apic);
+}
+
  void __init xen_init_apic(void)
  {
         x86_apic_ops.io_apic_read = xen_io_apic_read;
-       /* On PV guests the APIC CPUID bit is disabled so none of the
-        * routines end up executing. */
-       if (!xen_initial_domain())
-               apic_install_driver(&xen_pv_apic);
-
         x86_platform.apic_post_init = xen_apic_check;
  }
  apic_driver(xen_pv_apic);
diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
index c6b42c66c60c..ff2d0754ce62 100644
--- a/arch/x86/xen/smp_pv.c
+++ b/arch/x86/xen/smp_pv.c
@@ -188,6 +188,9 @@ static void __init _get_smp_config(unsigned int early)
  static void __init xen_pv_smp_prepare_boot_cpu(void)
  {
         BUG_ON(smp_processor_id() != 0);
+
+       xen_apic_install();
+
         native_smp_prepare_boot_cpu();

         if (!xen_feature(XENFEAT_writable_page_tables))
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 408a2aa66c69..217e4b625e4d 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -119,6 +119,7 @@ static inline void __init xen_init_vga(const struct 
dom0_vga_console_info *info,
  void xen_add_preferred_consoles(void);

  void __init xen_init_apic(void);
+void __init xen_apic_install(void);

  #ifdef CONFIG_XEN_EFI
  extern void xen_efi_init(struct boot_params *boot_params);


Juergen

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