# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Date 1172149429 0
# Node ID c0b1a3b54548d77aa0e0ff96a1fa778b3bc35855
# Parent 3f7e8c763b55b0a805928adcd43d7e2ea321b3e4
hvm: Turn stack-pointer comparison on shadow-emulate path into a
heuristic which we can allow to fail.
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
---
xen/arch/x86/mm/shadow/multi.c | 16 ++++++++++------
1 files changed, 10 insertions(+), 6 deletions(-)
diff -r 3f7e8c763b55 -r c0b1a3b54548 xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c Thu Feb 22 12:49:44 2007 +0000
+++ b/xen/arch/x86/mm/shadow/multi.c Thu Feb 22 13:03:49 2007 +0000
@@ -2909,7 +2909,7 @@ static int sh_page_fault(struct vcpu *v,
* stack is currently considered to be a page table, so we should
* unshadow the faulting page before exiting.
*/
- if ( hvm_injection_pending(v) )
+ if ( unlikely(hvm_injection_pending(v)) )
{
gdprintk(XENLOG_DEBUG, "write to pagetable during event "
"injection: cr2=%#lx, mfn=%#lx\n",
@@ -2925,16 +2925,20 @@ static int sh_page_fault(struct vcpu *v,
(unsigned long)regs->eip, (unsigned long)regs->esp);
/*
- * Check whether this looks like a stack operation.
- * If so, forcibly unshadow and return.
+ * Check whether this looks like a stack operation. If so, unshadow the
+ * faulting page. We can allow this to fail: if it does fail then we
+ * carry on and emulate, otherwise we bail immediately. Failure is
+ * tolerated because this is only a heuristic (e.g., stack segment base
+ * address is ignored).
*/
- if ( (va & PAGE_MASK) == (regs->esp & PAGE_MASK) )
+ if ( unlikely((va & PAGE_MASK) == (regs->esp & PAGE_MASK)) )
{
gdprintk(XENLOG_DEBUG, "guest stack is on a shadowed frame: "
"%%esp=%#lx, cr2=%#lx, mfn=%#lx\n",
(unsigned long)regs->esp, va, mfn_x(gmfn));
- sh_remove_shadows(v, gmfn, 0 /* thorough */, 1 /* must succeed */);
- goto done;
+ sh_remove_shadows(v, gmfn, 0 /* thorough */, 0 /* can fail */);
+ if ( !(mfn_to_page(gmfn)->count_info & PGC_page_table) )
+ goto done;
}
emul_ops = shadow_init_emulation(&emul_ctxt, regs);
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