linux-kernel - Re: [PATCH tip/sched/core] mm/early_ioremap: Adjust early_ioremap system

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Message-ID: <9408c89a-8c72-32a8-9b28-87cbfcf7bcaa@amd.com>
Date:   Fri, 16 Jun 2017 09:43:40 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH tip/sched/core] mm/early_ioremap: Adjust early_ioremap
 system_state check

On 6/16/2017 8:03 AM, Tom Lendacky wrote:
> On 6/16/2017 5:58 AM, Thomas Gleixner wrote:
>> On Wed, 14 Jun 2017, Tom Lendacky wrote:
>>> A recent change added a new system_state value, SYSTEM_SCHEDULING, which
>>> exposed a warning issued by early_ioreamp() when the system_state was 
>>> not
>>> SYSTEM_BOOTING. Since early_ioremap() can be called when the 
>>> system_state
>>> is SYSTEM_SCHEDULING, the check to issue the warning is changed from
>>> system_state != SYSTEM_BOOTING to system_state >= SYSTEM_RUNNING.
>>
>> Errm, why is that early_ioremap() stuff called after we enabled the
>> scheduler? At that point the regular ioremap stuff is long working.
> 
> As part of the SME support I'm decrypting the trampoline area during
> set_real_mode_permissions().  Since it was still valid to use the
> early_memremap()/early_ioremap() functions I chose to use those instead
> of creating new ioremap functions to support encrypted or decrypted
> mappings with and without write-protection.

Looking at this again, in setup_real_mode() I can update the trampoline
area with the proper encryption attributes using set_memory_decrypted()
before the trampoline area is copied and thus avoid having to decrypt
the area in-place.  With that I won't need to use the early_memremap()
functions.

So you can ignore this patch.

Thanks,
Tom

> 
> I could look into adding new ioremap APIs, but their usage would be
> limited to this one case.  Since the early_memremap() works I thought
> that would be the best path and just adjust the WARNing condition.
> 
> Thanks,
> Tom
> 
>>
>> Thanks,
>>
>>     tglx
>>
>>