# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1202920551 0
# Node ID ec1fa84147ad8c72018f976c953341a5fb657eac
# Parent 4c64376d439d3237e81f56b0fdfac7fe6601ec82
vmx realmode: __hvm_copy() should not hvm_get_segment_register() when
we are emulating. Firstly it is bogus, since VMCS segment state is
stale in this context. Secondly, real mode and real->protected
contexts are rather unlikely tohappen with SS.DPL == 3.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
xen/arch/x86/hvm/hvm.c | 23 +++++++++++++++++------
1 files changed, 17 insertions(+), 6 deletions(-)
diff -r 4c64376d439d -r ec1fa84147ad xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c Wed Feb 13 16:28:38 2008 +0000
+++ b/xen/arch/x86/hvm/hvm.c Wed Feb 13 16:35:51 2008 +0000
@@ -1386,6 +1386,7 @@ static enum hvm_copy_result __hvm_copy(
static enum hvm_copy_result __hvm_copy(
void *buf, paddr_t addr, int size, int dir, int virt, int fetch)
{
+ struct vcpu *curr = current;
unsigned long gfn, mfn;
p2m_type_t p2mt;
char *p;
@@ -1394,12 +1395,22 @@ static enum hvm_copy_result __hvm_copy(
if ( virt )
{
- struct segment_register sreg;
- hvm_get_segment_register(current, x86_seg_ss, &sreg);
- if ( sreg.attr.fields.dpl == 3 )
- pfec |= PFEC_user_mode;
+ /*
+ * We cannot use hvm_get_segment_register() while executing in
+ * vmx_realmode() as segment register state is cached. Furthermore,
+ * VMREADs on every data access hurts emulation performance.
+ */
+ if ( !curr->arch.hvm_vmx.vmxemul )
+ {
+ struct segment_register sreg;
+ hvm_get_segment_register(curr, x86_seg_ss, &sreg);
+ if ( sreg.attr.fields.dpl == 3 )
+ pfec |= PFEC_user_mode;
+ }
+
if ( dir )
pfec |= PFEC_write_access;
+
if ( fetch )
pfec |= PFEC_insn_fetch;
}
@@ -1411,7 +1422,7 @@ static enum hvm_copy_result __hvm_copy(
if ( virt )
{
- gfn = paging_gva_to_gfn(current, addr, &pfec);
+ gfn = paging_gva_to_gfn(curr, addr, &pfec);
if ( gfn == INVALID_GFN )
{
if ( virt == 2 ) /* 2 means generate a fault */
@@ -1435,7 +1446,7 @@ static enum hvm_copy_result __hvm_copy(
if ( dir )
{
memcpy(p, buf, count); /* dir == TRUE: *to* guest */
- paging_mark_dirty(current->domain, mfn);
+ paging_mark_dirty(curr->domain, mfn);
}
else
memcpy(buf, p, count); /* dir == FALSE: *from guest */
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