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[Xen-devel] Re: [RFC, PATCH 10/24] i386 Vmi descriptor changes
- To: Andi Kleen <ak@xxxxxxx>
- From: Zachary Amsden <zach@xxxxxxxxxx>
- Date: Wed, 22 Mar 2006 16:00:43 -0800
- Cc: Andrew Morton <akpm@xxxxxxxx>, Joshua LeVasseur <jtl@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Pratap Subrahmanyam <pratap@xxxxxxxxxx>, Wim Coekaerts <wim.coekaerts@xxxxxxxxxx>, Chris Wright <chrisw@xxxxxxxx>, Jack Lo <jlo@xxxxxxxxxx>, Dan Hecht <dhecht@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxxxx>, Christopher Li <chrisl@xxxxxxxxxx>, virtualization@xxxxxxxxxxxxxx, Linus Torvalds <torvalds@xxxxxxxx>, Anne Holler <anne@xxxxxxxxxx>, Jyothy Reddy <jreddy@xxxxxxxxxx>, Kip Macy <kmacy@xxxxxxxxxxx>, Ky Srinivasan <ksrinivasan@xxxxxxxxxx>, Leendert van Doorn <leendert@xxxxxxxxxxxxxx>, Dan Arai <arai@xxxxxxxxxx>
- Delivery-date: Thu, 23 Mar 2006 18:02:02 +0000
- List-id: Xen developer discussion <xen-devel.lists.xensource.com>
Andi Kleen wrote:
-#define _set_gate(gate_addr,type,dpl,addr,seg) \
-do { \
- int __d0, __d1; \
- __asm__ __volatile__ ("movw %%dx,%%ax\n\t" \
- "movw %4,%%dx\n\t" \
- "movl %%eax,%0\n\t" \
- "movl %%edx,%1" \
- :"=m" (*((long *) (gate_addr))), \
- "=m" (*(1+(long *) (gate_addr))), "=&a" (__d0), "=&d" (__d1) \
- :"i" ((short) (0x8000+(dpl<<13)+(type<<8))), \
- "3" ((char *) (addr)),"2" ((seg) << 16)); \
-} while (0)
The ugly piece of code doesn't do anything priviledged. So why do you want
to move it?
I didn't think I moved it. I wrote a clean version instead. It does do
something problematic for virtualization, by not allowing the VMI layer
to override the DPL on descriptors or RPL of segments. It might be
convenient for the hypervisor platform layer to do that.
Zach
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