答复: [Xen-devel] Why using hypercall_page ?

["Li Yaqiong" <liyaq04@xxxxxxxxxx>]

As you know, the old Intel/AMD x86 cpus use INT to invoke kernel's
service. But the newer CPUs introduce two instruction pairs:
syscall/sysret, syscenter/sysexit. So, because the hypercall page is
filled by Xen, it can hide the difference of this two types. Guest OS
only take one uniform format to invoke a hypercall.
I gusee this is the reason.

-Techie

-----邮件原件-----
发件人: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] 代表 Wu Bingzheng
发送时间: 2008年10月23日 9:18
收件人: xen-devel@xxxxxxxxxxxxxxxxxxx
主题: [Xen-devel] Why using hypercall_page ?

Hello,

I am studing Xen hypercall now. I found that hypercall is invoked via
hypercall_page, which is only filled with (in
no-hypervisor-kernel-mode ):

mov $i, %eax
int $0x82
ret

Why not invoked the hypercall directly by "int $0x82" ? What's the
advantage of using hypercall_page?

Thanks,
Wu


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