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Re: [PATCH v6] x86: detect CMOS aliasing on ports other than 0x70/0x71
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 19 Apr 2023 09:56:35 +0200
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Wed, 19 Apr 2023 07:57:15 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 18.04.2023 13:35, Roger Pau Monné wrote:
> On Tue, Apr 18, 2023 at 11:24:19AM +0200, Jan Beulich wrote:
>> ... in order to also intercept Dom0 accesses through the alias ports.
>>
>> Also stop intercepting accesses to the CMOS ports if we won't ourselves
>> use the CMOS RTC, because of there being none.
>>
>> Note that rtc_init() deliberately uses 16 as the upper loop bound,
>> despite probe_cmos_alias() using 8: The higher bound is benign now, but
>> would save us touching the code (or, worse, missing to touch it) in case
>> the lower one was doubled.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Thanks.
>> --- a/xen/arch/x86/pv/emul-priv-op.c
>> +++ b/xen/arch/x86/pv/emul-priv-op.c
>> @@ -208,7 +208,7 @@ static bool admin_io_okay(unsigned int p
>> return false;
>>
>> /* We also never permit direct access to the RTC/CMOS registers. */
>
> Hm, it's unclear to me whether the comment above would need updating:
> we don't allow direct access to the RTC/CMOS registers, but we allow
> direct access to the RTC/CMOS ports if there's no device behind.
Right, but those ports then don't allow access to said registers. So
I think the comment is fine as is.
Jan
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