... which is more consise than the opencoded form.
Also, for production VMs, ~100% of emulations are simple MOVs, so it is likely
that there are no segments to write back.
Furthermore, now that find_{first,next}_bit() are no longer in use, the
seg_reg_{accessed,dirty} fields aren't forced to be unsigned long, although
they do need to remain unsigned int because of __set_bit() elsewhere.
No practical change.
Signed-off-by: Andrew Cooper <[email protected]>
---
CC: Jan Beulich <[email protected]>
CC: Roger Pau Monné <[email protected]>
Pulling current out into curr is good for code generation. When using current
in the loop, GCC can't retain the calculation across the call to
hvm_set_segment_register() and is forced to re-read from the cpu_info block.
However, if curr is initialised, it's calculated even in the likely path...
---
xen/arch/x86/hvm/emulate.c | 20 ++++++++++----------
xen/arch/x86/include/asm/hvm/emulate.h | 4 ++--
2 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index feb4792cc567..732bdbab25b0 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -2908,18 +2908,18 @@ void hvm_emulate_init_per_insn(
void hvm_emulate_writeback(
struct hvm_emulate_ctxt *hvmemul_ctxt)
{
- enum x86_segment seg;
+ struct vcpu *curr;
+ unsigned int dirty = hvmemul_ctxt->seg_reg_dirty;
- seg = find_first_bit(&hvmemul_ctxt->seg_reg_dirty,
- ARRAY_SIZE(hvmemul_ctxt->seg_reg));
+ if ( likely(!dirty) )
+ return;
- while ( seg < ARRAY_SIZE(hvmemul_ctxt->seg_reg) )
- {
- hvm_set_segment_register(current, seg, &hvmemul_ctxt->seg_reg[seg]);
- seg = find_next_bit(&hvmemul_ctxt->seg_reg_dirty,
- ARRAY_SIZE(hvmemul_ctxt->seg_reg),
- seg+1);
- }
+ curr = current;
+
+ for_each_set_bit ( seg, dirty )
+ hvm_set_segment_register(curr, seg, &hvmemul_ctxt->seg_reg[seg]);
+
+ hvmemul_ctxt->seg_reg_dirty = 0;
}
/*
diff --git a/xen/arch/x86/include/asm/hvm/emulate.h
b/xen/arch/x86/include/asm/hvm/emulate.h
index 29d679442e10..972cdf1fa0cf 100644
--- a/xen/arch/x86/include/asm/hvm/emulate.h
+++ b/xen/arch/x86/include/asm/hvm/emulate.h
@@ -36,8 +36,8 @@ struct hvm_emulate_ctxt {
unsigned int insn_buf_bytes;
struct segment_register seg_reg[10];
- unsigned long seg_reg_accessed;
- unsigned long seg_reg_dirty;
+ unsigned int seg_reg_accessed;
+ unsigned int seg_reg_dirty;
/*
* MFNs behind temporary mappings in the write callback. The length is
--
2.39.2
