From: Arnd Bergmann <arnd@arndb.de>
To: kvm-devel@lists.sourceforge.net
Subject: Re: [kvm-devel] [PATCH] KVM: Avoid using vmx instruction directly
Date: Thu, 9 Nov 2006 14:29:41 +0100
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Cc: Avi Kivity <avi@qumranet.com>, akpm@osdl.org, linux-kernel@vger.kernel.org
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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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