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KVM: SVM: Let gcc to choose which registers to save (x86_64)

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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>
This commit is contained in:
Laurent Vivier 2007-10-25 14:18:53 +02:00 committed by Avi Kivity
parent ff593e5abe
commit 54a08c0449
1 changed files with 8 additions and 9 deletions
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17
drivers/kvm/svm.c
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@ -1499,10 +1499,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
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 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
"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 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
[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);