Laurent Vivier wrote: > As x86_64 ABI defines some registers saved by the calling function, it is not > needed to save all registers in the called function when switching to VCPU. > (see http://www.x86-64.org/documentation/abi.pdf, chapter 3.2.1) > > The best way to do that is to inform GCC which registers we use and let > it to save only needed registers. > >
Strange, yesterday I started to do the same thing but dropped it after I got discouraged by reload errors from gcc. > diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c > index 2c6b64a..d6c91ac 100644 > --- a/drivers/kvm/vmx.c > +++ b/drivers/kvm/vmx.c > @@ -2243,16 +2243,12 @@ 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. */ > @@ -2311,12 +2307,8 @@ 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" > @@ -2354,7 +2346,12 @@ 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 > + ); > The comma after "memory" worries me. Can you compile-test on i386? Other than that the patch is very welcome -- the excessive register saving is very annoying to me. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
