[Xen-ia64-devel] RE: [PATCH 04/15] ia64/pv_ops: introduce pv_info which describes some random info. - Dong, Eddie - com.xensource.lists.xen-ia64-devel

32 messages in com.xensource.lists.xen-ia64-devel[Xen-ia64-devel] RE: [PATCH 04/15] ia...

From	Sent On	Attachments
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Isaku Yamahata	08 Apr 2008 21:48
Jes Sorensen	22 Apr 2008 02:07
Jes Sorensen	22 Apr 2008 02:16
Isaku Yamahata	22 Apr 2008 03:01
Isaku Yamahata	22 Apr 2008 03:10
Jes Sorensen	22 Apr 2008 03:36
Dong, Eddie	22 Apr 2008 03:41
Isaku Yamahata	22 Apr 2008 04:01
Jes Sorensen	22 Apr 2008 04:29
Jes Sorensen	22 Apr 2008 05:05
Dong, Eddie	22 Apr 2008 06:15
Jes Sorensen	22 Apr 2008 06:55
Isaku Yamahata	22 Apr 2008 19:53
Jes Sorensen	23 Apr 2008 07:03
Isaku Yamahata	24 Apr 2008 04:18
Jes Sorensen	24 Apr 2008 04:51
Isaku Yamahata	24 Apr 2008 05:21

Subject:	[Xen-ia64-devel] RE: [PATCH 04/15] ia64/pv_ops: introduce pv_info which describes some random info.
From:	Dong, Eddie (eddi...@intel.com)
Date:	04/22/2008 06:15:03 AM
List:	com.xensource.lists.xen-ia64-devel

Jes Sorensen wrote:

Dong, Eddie wrote:

Rather than making these binary patches, why not make them fast syscalls and using a vdso page. Some of the priviledged instructions are simply reads and we could have that information in a read-only data page, so there is no need to do a context switch at all. Others could benefit from a fast system call that doesn't do a full context switch.

The issue is we don't want to change Linux code a lot, otherwise it won't be accepted. If we use same logic with original Linux, but it is using indirect function call now, binary patching could help in performance.

Hi Eddie,

Sorry but this is a wrong assumption. If the code is correct then there is no reason why it will not be accepted. It's far more important to avoid ugly clutter that makes the code hard to maintain.

My understanding is that code such as IVT table are well tuned and you are really difficult to pursuade people to replace those privilege resource access instruction to use vdso or something equalvalent such as mov GRx=CRy. For those C code previlige resource access, like Isaku mentioned, we need to consider native too.

Anyway binary patching is just an optimization that X86 used and there is no reason IA64 can't take. At least replacing indirect function with direct function call.

Eddie