Re: [Xen-devel] [PATCH] Fix Vista screen clear on AMD

[Ben Guthro <bguthro@xxxxxxxxxxxxxxx>]

hmm,

Its certainly possiible that I ported this incorrectly to unstable. I have attached the original patch that applies to 3.1.1 for your review. As for the details on why this patch was written this way - I will let the original author field that (Gary)

If this is not necessary anymore, as you said below - perhaps this code should be removed entirely?

Ben

Tim Deegan wrote:

Hi Ben, Gary,

At 17:07 -0400 on 24 Oct (1193245642), Ben Guthro wrote:
  

Patch to fix horribly slow screen clear during Vista 32 installation
on AMD.
    

Can you explain what the patch does?  It seems to extend the need for
extra update_cr3() calls to the 64bit hypervisor case and then cause it
never to happen at all.

  

diff -r 64544443e6d6 xen/arch/x86/mm/shadow/common.c
--- a/xen/arch/x86/mm/shadow/common.c	Wed Oct 10 11:10:36 2007 -0400
+++ b/xen/arch/x86/mm/shadow/common.c	Wed Oct 10 12:50:46 2007 -0400
@@ -36,6 +36,7 @@
 #include <asm/current.h>
 #include <asm/flushtlb.h>
 #include <asm/shadow.h>
+#include <asm/paging.h>
    

Inside shadow code, it's best to use the shadow_* versions of things.
The paging_* ones will just check for being in shadow mode, which we
know is true.

  

 #include "private.h"
 
 
@@ -2725,17 +2726,18 @@ shadow_write_p2m_entry(struct vcpu *v, u
     safe_write_pte(p, new);
 
     /* install P2M in monitors for PAE Xen */
-#if CONFIG_PAGING_LEVELS == 3
+#if CONFIG_PAGING_LEVELS >= 3
     if ( level == 3 ) {
         struct vcpu *v;
+#if CONFIG_PAGING_LEVELS == 3
         /* We have written to the p2m l3: need to sync the per-vcpu
          * copies of it in the monitor tables */
         p2m_install_entry_in_monitors(d, (l3_pgentry_t *)p);
+#endif
         /* Also, any vcpus running on shadows of the p2m need to 
          * reload their CR3s so the change propagates to the shadow */
         for_each_vcpu(d, v) {
-            if ( pagetable_get_pfn(v->arch.guest_table) 
-                 == pagetable_get_pfn(d->arch.phys_table) 
+            if ( likely(!paging_mode_translate(d))
    

This test will never be true; if you aren't in paging_mode_translate()
you won't be writing p2m entries in the first place.

That said, I think it's probably right to just get rid of the call
entirely, since we don't shadow the p2m any more. 

Cheers,

Tim.

  

diff -r 16bf26cdf06b xen/arch/x86/mm/shadow/common.c
--- a/xen/arch/x86/mm/shadow/common.c   Tue Jul 24 16:49:50 2007 -0400
+++ b/xen/arch/x86/mm/shadow/common.c   Tue Jul 24 16:49:53 2007 -0400
@@ -2891,17 +2891,18 @@ shadow_write_p2m_entry(struct vcpu *v, u
         (void)sh_validate_guest_entry(d->vcpu[0], table_mfn, p, sizeof(*p));
 
     /* install P2M in monitors for PAE Xen */
-#if CONFIG_PAGING_LEVELS == 3
+#if CONFIG_PAGING_LEVELS >= 3
     if ( level == 3 ) {
         struct vcpu *v;
+#if CONFIG_PAGING_LEVELS == 3
         /* We have written to the p2m l3: need to sync the per-vcpu
          * copies of it in the monitor tables */
         p2m_install_entry_in_monitors(d, (l3_pgentry_t *)p);
+#endif
         /* Also, any vcpus running on shadows of the p2m need to 
          * reload their CR3s so the change propagates to the shadow */
         for_each_vcpu(d, v) {
-            if ( pagetable_get_pfn(v->arch.guest_table) 
-                 == pagetable_get_pfn(d->arch.phys_table) 
+            if ( ! v->arch.paging.translate_enabled
                  && v->arch.paging.mode != NULL )
                 v->arch.paging.mode->update_cr3(v, 0);
         }

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