RE: [Xen-ia64-devel] [PATCH][RFC][TAKE4] the P2M/VP patches

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

>From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
>[mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Alex
>Williamson
>Sent: 2006?4?12? 23:29
>To: Tristan Gingold
>Cc: Isaku Yamahata; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
>Subject: Re: [Xen-ia64-devel] [PATCH][RFC][TAKE4] the P2M/VP patches
>
>On Wed, 2006-04-12 at 09:01 +0100, Tristan Gingold wrote:
>
>> > Last, the only way to prevent such io access is from guest itself,
>> > meant not compiling native drivers in. Or else there's no way for
>> > xen to handle it correctly.
>> User should disable drivers in domU.  Everybody agree with that!
>
>   I don't.  Xen needs to handle this better.  domU I/O port space
>should be mapped to fault on access.  Writes should be dropped and reads
>return -1.  This is how a legacy system would behave.  We don't really
>care about performance here, I/O port space is already slow, and this is
>really only meant to handle startup time probing.  IMHO, it's
>unreasonable to ask users to disable all drivers or even try to tell
>them what that means.  The Linux/ia64 kernel currently does a pretty
>good job of not blindly probing address spaces looking for hardware.  I
>think as long as we handle I/O port space reasonably, we'll make the
>driver situation in domU more flexible.  Thanks,
>
>       Alex

HASH-VTLB has already handled IO-PORT and IO-MM,
HASH-VTLB records guest IO-PORT or IO-MM translation of guest, 
but not insert this translation into machine VHPT or machine TLB,
thus, every time guest accesses IO, tlb miss happens.
Now, it is up to VMM to handle guest IO operations.

Thanks,
Anthony



>
>--
>Alex Williamson                             HP Linux & Open Source Lab
>
>
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