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Re: [Xen-devel] [PATCH 3/3] xen/x86: ioapic: Simplify ioapic_init()



Hi Wei,

On 29/03/2020 15:35, Wei Liu wrote:
On Fri, Mar 27, 2020 at 07:05:46PM +0000, Julien Grall wrote:
From: Julien Grall <jgrall@xxxxxxxxxx>

Since commit 9facd54a45 "x86/ioapic: Add register level checks to detect
bogus io-apic entries", Xen is able to cope with IO APICs not mapped in
the fixmap.

Therefore the whole logic to allocate a fake page for some IO APICs is
unnecessary.

With the logic removed, the code can be simplified a lot as we don't
need to go through all the IO APIC if SMP has not been detected or a
bogus zero IO-APIC address has been detected.

To avoid another level of tabulation, the simplification is now moved in
its own function.

Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
---
  xen/arch/x86/io_apic.c | 63 ++++++++++++++++++++----------------------
  1 file changed, 30 insertions(+), 33 deletions(-)

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index 9a11ee8342..3d52e4daf1 100644
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -2537,34 +2537,25 @@ static __init bool bad_ioapic_register(unsigned int idx)
      return false;
  }
-void __init init_ioapic(void)
+static void __init init_ioapic_mappings(void)
  {
-    unsigned long ioapic_phys;
      unsigned int i, idx = FIX_IO_APIC_BASE_0;
-    union IO_APIC_reg_01 reg_01;
- if ( smp_found_config )
-        nr_irqs_gsi = 0;
      for ( i = 0; i < nr_ioapics; i++ )
      {
-        if ( smp_found_config )
-        {
-            ioapic_phys = mp_ioapics[i].mpc_apicaddr;
-            if ( !ioapic_phys )
-            {
-                printk(KERN_ERR "WARNING: bogus zero IO-APIC address "
-                       "found in MPTABLE, disabling IO/APIC support!\n");
-                smp_found_config = false;
-                skip_ioapic_setup = true;
-                goto fake_ioapic_page;
-            }
-        }
-        else
+        union IO_APIC_reg_01 reg_01;
+        unsigned long ioapic_phys = mp_ioapics[i].mpc_apicaddr;
+
+        ioapic_phys = mp_ioapics[i].mpc_apicaddr;

ioapic_phys is set a second time here. See the line before.

Good spot! I will drop the line.

Cheers,

--
Julien Grall



 


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