Re: [PATCH] x86/speculation/l1tf: suggest what to do on systems with too much RAM

[Vlastimil Babka]

On 08/23/2018 09:27 PM, Michal Hocko wrote:
> On Thu 23-08-18 16:28:12, Vlastimil Babka wrote:
>> Two users have reported [1] that they have an "extremely unlikely" system
>> with more than MAX_PA/2 memory and L1TF mitigation is not effective. Let's
>> make the warning more helpful by suggesting the proper mem=X kernel boot param,
>> a rough calculation of how much RAM can be lost (not precise if there's holes
>> between MAX_PA/2 and max_pfn in the e820 map) and a link to the L1TF document
>> to help decide if the mitigation is worth the unusable RAM.
>>
>> [1] https://bugzilla.suse.com/show_bug.cgi?id=1105536
>>
>> Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
>> Cc: stable@xxxxxxxxxxxxxxx
>> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> 
> I wouldn't bother with max_pfn-half_pa part but other than that this is
> much more useful than the original message.

Right, and it causes build failures on some configs.

> Acked-by: Michal Hocko <mhocko@xxxxxxxx>

Thanks! Here's a v2:

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