KVM: VMX: Let gcc to choose which registers to save (i386)
This patch lets GCC to determine which registers to save when we
switch to/from a VCPU in the case of intel i386.
* Original code saves following registers:
eax, ebx, ecx, edx, edi, esi, ebp (using popa)
* Patched code:
- informs GCC that we modify following registers
using the clobber description:
ebx, edi, rsi
- doesn't save eax because it is an output operand (vmx->fail)
- cannot put ecx in clobber description because it is an input operand,
but as we modify it and we want to keep its value (vcpu), we must
save it (pop/push)
- ebp is saved (pop/push) because GCC seems to ignore its use the clobber
description.
- edx is saved (pop/push) because it is reserved by GCC (REGPARM) and
cannot be put in the clobber description.
- line "mov (%%esp), %3 \n\t" has been removed because %3
is ecx and ecx is restored just after.
Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>
1 file changed