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Re: [PATCH][4.17] EFI: don't convert memory marked for runtime use to ordinary RAM
- To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- Date: Tue, 11 Oct 2022 07:52:02 +0000
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- Cc: Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>, Henry Wang <Henry.Wang@xxxxxxx>
- Delivery-date: Tue, 11 Oct 2022 07:52:42 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH][4.17] EFI: don't convert memory marked for runtime use to ordinary RAM
Hi,
> On 11 Oct 2022, at 00:58, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
>
> On Mon, 10 Oct 2022, Jan Beulich wrote:
>> On 08.10.2022 21:08, Julien Grall wrote:
>>> On 06/10/2022 15:11, Jan Beulich wrote:
>>>>> ... the space cannot become ordinary RAM, then such a precaution
>>>>> wouldn't be necessary. After all hiding EfiACPIReclaimMemory from
>>>>> Dom0 just because it can't be mapped WB wouldn't be very nice
>>>>> either. I guess I'll submit v2 with this part of the change left
>>>>> as it was.
>>>>
>>>> And while already in the process of committing the patch I came to
>>>> realize that if the WB conditional isn't supposed to move, isn't
>>>> the change done for Arm then wrong as well? Shouldn't it then be
>>>>
>>>> if ( !(desc_ptr->Attribute & EFI_MEMORY_RUNTIME) &&
>>>> (desc_ptr->Attribute & EFI_MEMORY_WB) &&
>>>> (desc_ptr->Type == EfiConventionalMemory ||
>>>> ...
>>>>
>>>> leaving the EfiACPIReclaimMemory case entirely unaffected by the
>>>> change?
>>>
>>> IIUC, the concern is the region EfiACPIReclaimMemory could have the
>>> attribute EFI_MEMORY_RUNTIME. Is that correct?
>>
>> Yes, ...
>>
>>> Given that the memory is reclaimable, I am not sure why it can also have
>>> this atribute set (to me it means the opposite).
>>
>> ... at least on x86 all sorts of strange/bogus type/attribute combinations
>> have been observed.
>
> Yeah... it is a good idea to be able to cope with strange and bogus
> firmware tables as it is known to happen
I agree with that but if we make an assumption that something is bogus, we
should at least warn the user if possible.
Bertrand
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