Re: [PATCH] KVM: Avoid using vmx instruction directly

Arnd Bergmann
2006-11-09T13:29:41Z

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)'?

Arnd <><

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