KVM: SVM: Let gcc to choose which registers to save (x86_64)
This patch lets GCC to determine which registers to save when we
switch to/from a VCPU in the case of AMD x86_64.
* Original code saves following registers:
rbx, rcx, rdx, rsi, rdi, rbp,
r8, r9, r10, r11, r12, r13, r14, r15
* Patched code:
- informs GCC that we modify following registers
using the clobber description:
rbx, rcx, rdx, rsi, rdi
r8, r9, r10, r11, r12, r13, r14, r15
- rbp is saved (pop/push) because GCC seems to ignore its use in the clobber
description.
Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
index beb1e68..debd091 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -1499,10 +1499,7 @@
asm volatile (
#ifdef CONFIG_X86_64
- "push %%rbx; push %%rcx; push %%rdx;"
- "push %%rsi; push %%rdi; push %%rbp;"
- "push %%r8; push %%r9; push %%r10; push %%r11;"
- "push %%r12; push %%r13; push %%r14; push %%r15;"
+ "push %%rbp; \n\t"
#else
"push %%ebx; push %%ecx; push %%edx;"
"push %%esi; push %%edi; push %%ebp;"
@@ -1567,10 +1564,7 @@
"mov %%r14, %c[r14](%[svm]) \n\t"
"mov %%r15, %c[r15](%[svm]) \n\t"
- "pop %%r15; pop %%r14; pop %%r13; pop %%r12;"
- "pop %%r11; pop %%r10; pop %%r9; pop %%r8;"
- "pop %%rbp; pop %%rdi; pop %%rsi;"
- "pop %%rdx; pop %%rcx; pop %%rbx; \n\t"
+ "pop %%rbp; \n\t"
#else
"mov %%ebx, %c[rbx](%[svm]) \n\t"
"mov %%ecx, %c[rcx](%[svm]) \n\t"
@@ -1601,7 +1595,12 @@
[r14]"i"(offsetof(struct vcpu_svm, vcpu.regs[VCPU_REGS_R14])),
[r15]"i"(offsetof(struct vcpu_svm, vcpu.regs[VCPU_REGS_R15]))
#endif
- : "cc", "memory");
+ : "cc", "memory"
+#ifdef CONFIG_X86_64
+ , "rbx", "rcx", "rdx", "rsi", "rdi"
+ , "r8", "r9", "r10", "r11" , "r12", "r13", "r14", "r15"
+#endif
+ );
if ((svm->vmcb->save.dr7 & 0xff))
load_db_regs(svm->host_db_regs);