linux-kernel - Re: [PATCH Part2 v6 07/49] x86/sev: Invalid pages from direct map when adding it to RMP table

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Message-ID: <6e9f3d48-1777-6710-cb1d-3f2f38c0328e@amd.com>
Date:   Tue, 1 Nov 2022 22:12:35 -0500
From:   "Kalra, Ashish" <ashish.kalra@....com>
To:     Borislav Petkov <bp@...en8.de>
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Subject: Re: [PATCH Part2 v6 07/49] x86/sev: Invalid pages from direct map
 when adding it to RMP table

Hello Boris,

On 8/4/2022 7:11 AM, Borislav Petkov wrote:
> On Mon, Aug 01, 2022 at 11:57:09PM +0000, Kalra, Ashish wrote:
>> You mean set_memory_present() ?
> 
> Right, that.
> 
> We have set_memory_np() but set_memory_present(). Talk about
> consistence... ;-\

Following up on this, now, set_memory_present() is a static interface,
so will need do add a new external API like set_memory_p() similar
to set_memory_np().

Also, looking at arch/x86/include/asm/set_memory.h:
..
/*
  * The set_memory_* API can be used to change various attributes of a
  * virtual address range. The attributes include:
  * Cacheability  : UnCached, WriteCombining, WriteThrough, WriteBack
  * Executability : eXecutable, NoteXecutable
  * Read/Write    : ReadOnly, ReadWrite
  * Presence      : NotPresent
  * Encryption    : Encrypted, Decrypted
  *
..
int set_memory_np(unsigned long addr, int numpages);
..

So currently there is no interface defined for changing the attribute of 
a range to present or restoring the range in the direct map.

Thanks,
Ashish