Re: [kvm-devel] [PATCH] KVM: Avoid using vmx instruction directly

[Avi Kivity]

Arnd Bergmann wrote:
> On Thursday 09 November 2006 12:08, Avi Kivity wrote:
>   
> > Index: linux-2.6/drivers/kvm/kvm_main.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/kvm/kvm_main.c
> > +++ linux-2.6/drivers/kvm/kvm_main.c
> > @@ -369,8 +369,8 @@ static void vmcs_clear(struct vmcs *vmcs
> >         u64 phys_addr = __pa(vmcs);
> >         u8 error;
> >  
> > -       asm volatile ("vmclear %1; setna %0"
> > -                      : "=m"(error) : "m"(phys_addr) : "cc", "memory" );
> > +       asm volatile (ASM_VMX_VMCLEAR_RAX "; setna %0"
> > +                      : "=g"(error) : "a"(&phys_addr) : "cc", "memory" );
> >         if (error)
> >                 printk(KERN_ERR "kvm: vmclear fail: %p/%llx\n",
> >                        vmcs, phys_addr);
> >     
>
> I'm not an expert on inline assembly, but don't you need an extra
> '"m" (phys_addr)' to make sure that gcc actually puts the variable
> on the stack instead of passing a NULL pointer as '"a"(&phys_addr)'?
>
>   

Taking a variable's address should force its contents into memory (like 
calling an uninlined function with &var).


--
error compiling committee.c: too many arguments to function

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