[Xen-devel] [PATCH v2 2/6] x86/xpti: don't flush TLB twice when switching to 64-bit pv context

[Juergen Gross <jgross@xxxxxxxx>]

When switching to a 64-bit pv context the TLB is flushed twice today:
the first time when switching to the new address space in
write_ptbase(), the second time when switching to guest mode in
restore_to_guest.

Avoid the first TLB flush in that case.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/mm.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index fdc1636817..cf512ee306 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -123,6 +123,7 @@
 #include <asm/io_apic.h>
 #include <asm/pci.h>
 #include <asm/guest.h>
+#include <asm/processor.h>
 
 #include <asm/hvm/grant_table.h>
 #include <asm/pv/grant_table.h>
@@ -509,9 +510,16 @@ void make_cr3(struct vcpu *v, mfn_t mfn)
 
 void write_ptbase(struct vcpu *v)
 {
-    get_cpu_info()->root_pgt_changed = this_cpu(root_pgt) && is_pv_vcpu(v) &&
-                                       !is_pv_32bit_vcpu(v);
-    write_cr3(v->arch.cr3);
+    if ( this_cpu(root_pgt) && is_pv_vcpu(v) && !is_pv_32bit_vcpu(v) )
+    {
+        get_cpu_info()->root_pgt_changed = true;
+        asm volatile ( "mov %0, %%cr3" : : "r" (v->arch.cr3) : "memory" );
+    }
+    else
+    {
+        get_cpu_info()->root_pgt_changed = false;
+        write_cr3(v->arch.cr3);
+    }
 }
 
 /*
-- 
2.13.6


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