From c20363006af64cf397519da5e984b18e6bdffd82 Mon Sep 17 00:00:00 2001 From: Laurent Vivier Date: Thu, 25 Oct 2007 14:18:52 +0200 Subject: [PATCH] KVM: VMX: 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 intel x86_64. * Original code saves following registers: rax, 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, rdi, rsi, r8, r9, r10, r11, r12, r13, r14, r15 - doesn't save rax because it is an output operand (vmx->fail) - cannot put rcx 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) - rbp is saved (pop/push) because GCC seems to ignore its use in the clobber description. - rdx is saved (pop/push) because it is reserved by GCC (REGPARM) and cannot be put in the clobber description. - line "mov (%%rsp), %3 \n\t" has been removed because %3 is rcx and rcx is restored just after. - line ASM_VMX_VMWRITE_RSP_RDX() is moved out of the ifdef/else/endif Signed-off-by: Laurent Vivier Signed-off-by: Avi Kivity --- drivers/kvm/vmx.c | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c index 46b29184a4..56c9bcc828 100644 --- a/drivers/kvm/vmx.c +++ b/drivers/kvm/vmx.c @@ -2265,16 +2265,12 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) asm( /* Store host registers */ #ifdef CONFIG_X86_64 - "push %%rax; push %%rbx; 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 %%rdx; push %%rbp;" "push %%rcx \n\t" - ASM_VMX_VMWRITE_RSP_RDX "\n\t" #else "pusha; push %%ecx \n\t" - ASM_VMX_VMWRITE_RSP_RDX "\n\t" #endif + ASM_VMX_VMWRITE_RSP_RDX "\n\t" /* Check if vmlaunch of vmresume is needed */ "cmp $0, %1 \n\t" /* Load guest registers. Don't clobber flags. */ @@ -2333,12 +2329,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) "mov %%r15, %c[r15](%3) \n\t" "mov %%cr2, %%rax \n\t" "mov %%rax, %c[cr2](%3) \n\t" - "mov (%%rsp), %3 \n\t" - "pop %%rcx; 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 %%rbx; pop %%rax \n\t" + "pop %%rcx; pop %%rbp; pop %%rdx \n\t" #else "xchg %3, (%%esp) \n\t" "mov %%eax, %c[rax](%3) \n\t" @@ -2376,7 +2368,12 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) [r15]"i"(offsetof(struct kvm_vcpu, regs[VCPU_REGS_R15])), #endif [cr2]"i"(offsetof(struct kvm_vcpu, cr2)) - : "cc", "memory"); + : "cc", "memory" +#ifdef CONFIG_X86_64 + , "rbx", "rdi", "rsi" + , "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15" +#endif + ); vcpu->interrupt_window_open = (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & 3) == 0; -- 2.39.5