[Xen-changelog] [xen staging] x86/boot: Drop vestigial support for pre-SIPI APICs

[patchbot@xxxxxxx]

commit 63dc4209d2420f68ef5783f8405ee7884072fcc0
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Jun 12 11:28:05 2019 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Jun 12 15:54:29 2019 +0100

    x86/boot: Drop vestigial support for pre-SIPI APICs
    
    The current code in do_boot_cpu() makes a CMOS write (even in the case of an
    FADT reduced hardware configuration) and two writes into the BDA for the
    start_eip segment and offset.
    
    BDA 0x67 and 0x69 hail from the days of the DOS and the 286, when IBM put
    together the fast way to return from Protected Mode back to Real Mode (via a
    deliberate triple fault).  This vector, when set, redirects the early boot
    logic back into OS control.
    
    It is also used by early MP systems, before the Startup IPI message became
    standard, which in practice was before Local APICs became integrated into 
CPU
    cores.
    
    Support for non-integrated APICs was dropped in c/s 7b0007af "xen/x86: 
Remove
    APIC_INTEGRATED() checks" because there are no 64-bit capable systems 
without
    them.  Therefore, drop smpboot_{setup,restore}_warm_reset_vector().
    
    Dropping smpboot_setup_warm_reset_vector() also lets us drop
    TRAMPOLINE_{HIGH,LOW}, which lets us drop mach_wakecpu.h entirely.  The 
final
    function in smpboot_hooks.h is smpboot_setup_io_apic() and has a single
    caller, so expand it inline and delete smpboot_hooks.h as well.
    
    This removes all reliance on CMOS and the BDA from the AP boot path, which 
is
    especially of interest on reduced_hardware boots and EFI systems.
    
    This was discovered while investigating Xen's use of the BDA during kexec.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/smpboot.c                           | 11 +-----
 xen/include/asm-x86/mach-default/mach_wakecpu.h  | 12 ------
 xen/include/asm-x86/mach-default/smpboot_hooks.h | 47 ------------------------
 3 files changed, 2 insertions(+), 68 deletions(-)

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 274865a705..730fe141fa 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -46,8 +46,6 @@
 #include <asm/time.h>
 #include <asm/tboot.h>
 #include <mach_apic.h>
-#include <mach_wakecpu.h>
-#include <smpboot_hooks.h>
 
 #define setup_trampoline()    (bootsym_phys(trampoline_realmode_entry))
 
@@ -565,10 +563,6 @@ static int do_boot_cpu(int apicid, int cpu)
 
     set_cpu_state(CPU_STATE_INIT);
 
-    Dprintk("Setting warm reset code and vector.\n");
-
-    smpboot_setup_warm_reset_vector(start_eip);
-
     /* Starting actual IPI sequence... */
     if ( !tboot_in_measured_env() || tboot_wake_ap(apicid, start_eip) )
         boot_error = wakeup_secondary_cpu(apicid, start_eip);
@@ -623,8 +617,6 @@ static int do_boot_cpu(int apicid, int cpu)
     bootsym(trampoline_cpu_started) = 0;
     smp_mb();
 
-    smpboot_restore_warm_reset_vector();
-
     return rc;
 }
 
@@ -1162,7 +1154,8 @@ void __init smp_prepare_cpus(void)
     connect_bsp_APIC();
     setup_local_APIC();
 
-    smpboot_setup_io_apic();
+    if ( !skip_ioapic_setup && nr_ioapics )
+        setup_IO_APIC();
 
     setup_boot_APIC_clock();
 }
diff --git a/xen/include/asm-x86/mach-default/mach_wakecpu.h 
b/xen/include/asm-x86/mach-default/mach_wakecpu.h
deleted file mode 100644
index 32555e1022..0000000000
--- a/xen/include/asm-x86/mach-default/mach_wakecpu.h
+++ /dev/null
@@ -1,12 +0,0 @@
-#ifndef __ASM_MACH_WAKECPU_H
-#define __ASM_MACH_WAKECPU_H
-
-/* 
- * This file copes with machines that wakeup secondary CPUs by the
- * INIT, INIT, STARTUP sequence.
- */
-
-#define TRAMPOLINE_LOW maddr_to_virt(0x467)
-#define TRAMPOLINE_HIGH maddr_to_virt(0x469)
-
-#endif /* __ASM_MACH_WAKECPU_H */
diff --git a/xen/include/asm-x86/mach-default/smpboot_hooks.h 
b/xen/include/asm-x86/mach-default/smpboot_hooks.h
deleted file mode 100644
index 14e1ee52a3..0000000000
--- a/xen/include/asm-x86/mach-default/smpboot_hooks.h
+++ /dev/null
@@ -1,47 +0,0 @@
-/* two abstractions specific to kernel/smpboot.c, mainly to cater to visws
- * which needs to alter them. */
-
-static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)
-{
-       unsigned long flags;
-
-       spin_lock_irqsave(&rtc_lock, flags);
-       CMOS_WRITE(0xa, 0xf);
-       spin_unlock_irqrestore(&rtc_lock, flags);
-       flush_tlb_local();
-       Dprintk("1.\n");
-       *((volatile unsigned short *) TRAMPOLINE_HIGH) = start_eip >> 4;
-       Dprintk("2.\n");
-       *((volatile unsigned short *) TRAMPOLINE_LOW) = start_eip & 0xf;
-       Dprintk("3.\n");
-}
-
-static inline void smpboot_restore_warm_reset_vector(void)
-{
-       unsigned long flags;
-
-       /*
-        * Install writable page 0 entry to set BIOS data area.
-        */
-       flush_tlb_local();
-
-       /*
-        * Paranoid:  Set warm reset code and vector here back
-        * to default values.
-        */
-       spin_lock_irqsave(&rtc_lock, flags);
-       CMOS_WRITE(0, 0xf);
-       spin_unlock_irqrestore(&rtc_lock, flags);
-
-       *((volatile int *) maddr_to_virt(0x467)) = 0;
-}
-
-static inline void smpboot_setup_io_apic(void)
-{
-       /*
-        * Here we can be sure that there is an IO-APIC in the system. Let's
-        * go and set it up:
-        */
-       if (!skip_ioapic_setup && nr_ioapics)
-               setup_IO_APIC();
-}
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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