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

From: Avi Kivity
Date: Thu Nov 09 2006 - 08:36:54 EST


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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