On 08/08/2010 05:27 AM, Mohammed Gamal wrote:
This adds unary mul, imul, div, and idiv instructions (group 3 r/m 4-7).
Signed-off-by: Mohammed Gamal<m.gamal005@xxxxxxxxx>
---
arch/x86/kvm/emulate.c | 41 ++++++++++++++++++++++++++++++++++++++++-
1 files changed, 40 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 7d78832..6d1ec53 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -315,6 +315,31 @@ struct group_dual {
} \
} while (0)
+#define __emulate_1op_src(_op, _src, _ax, _dx, _eflags, _suffix) \
Not just 1op - add rax_rdx to the name to indicate these are implicit
operands.
+ do { \
+ unsigned long _tmp; \
+ \
+ __asm__ __volatile__ ( \
+ _PRE_EFLAGS("0", "4", "1") \
+ _op _suffix " %5; " \
+ _POST_EFLAGS("0", "4", "1") \
+ : "=m" (_eflags), "=&r" (_tmp), \
+ "=a" (_ax), "=d" (_dx) \
+ : "i" (EFLAGS_MASK), "m" ((_src).val), \
+ "a" (_ax), "d" (_dx)); \
+ } while (0)
The byte form of the instruction doesn't update dx, and the word form
doesn't update edx[16:31]. So the "=a" and "=d" operands need to be
"+a" and "+d" so the compiler loads them before the operation is started.
Please add a test to the effect, for example start with eax=0x12345678,
and multiply (byte size) 0x80 by 0x40, and observe that the upper 16
bits of eax are preserved (and that rdx is not modified).
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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