[Xen-devel] [PATCH 1/5] x86/traps: Drop paging_mode_external() handling from the PV pagefault path

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

PV guests necessarily can't be external, as Xen must steal address space from
them.  Pagefaults for HVM guests are handled by {vmx,svm}_vmexit_handler() and
don't enter the PV fixup_page_fault() path.

This paging_fault() callsite is therefore dead code, so drop it.

Clarify the comment at the other paging_fault() callsite to indicate that it
covers the logdirty case only.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
---
 xen/arch/x86/traps.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 013e633..b20faa4 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1799,15 +1799,6 @@ static int fixup_page_fault(unsigned long addr, struct 
cpu_user_regs *regs)
     if ( in_irq() || !(regs->eflags & X86_EFLAGS_IF) )
         return 0;
 
-    /* Faults from external-mode guests are handled by shadow/hap */
-    if ( paging_mode_external(d) && guest_mode(regs) )
-    {
-        int ret = paging_fault(addr, regs);
-        if ( ret == EXCRET_fault_fixed )
-            trace_trap_two_addr(TRC_PV_PAGING_FIXUP, regs->eip, addr);
-        return ret;
-    }
-
     if ( !(regs->error_code & PFEC_page_present) &&
           (pagefault_by_memadd(addr, regs)) )
         return handle_memadd_fault(addr, regs);
@@ -1838,8 +1829,11 @@ static int fixup_page_fault(unsigned long addr, struct 
cpu_user_regs *regs)
             return EXCRET_fault_fixed;
     }
 
-    /* For non-external shadowed guests, we fix up both their own 
-     * pagefaults and Xen's, since they share the pagetables. */
+    /*
+     * For non-external shadowed guests (i.e. PV guests with logdirty
+     * active), we fix up both their own pagefaults and Xen's, since
+     * they share the pagetables.
+     */
     if ( paging_mode_enabled(d) && !paging_mode_external(d) )
     {
         int ret = paging_fault(addr, regs);
-- 
2.1.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel