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Re: [PATCH v2 2/3] x86: detect PIC aliasing on ports other than 0x[2A][01]


  • To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Jason Andryuk <jason.andryuk@xxxxxxx>
  • Date: Thu, 9 May 2024 12:06:40 -0400
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Thu, 09 May 2024 16:07:04 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 2023-12-18 09:48, Jan Beulich wrote:
... in order to also deny Dom0 access through the alias ports. Without
this it is only giving the impression of denying access to both PICs.
Unlike for CMOS/RTC, do detection very early, to avoid disturbing normal
operation later on.

Like for CMOS/RTC a fundamental assumption of the probing is that reads
from the probed alias port won't have side effects in case it does not
alias the respective PIC's one.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Code-wise
Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>

I appreciate what Jan is trying to achieve. I also share Roger's concern about reading IO ports since we don't know what is there.

I also don't have a good alternative to suggest...

Regards,
Jason



 


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