linux-kernel - Re: [PATCH 08/30] x86, kaiser: unmap kernel from userspace page tables (core patch)

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Date:   Wed, 22 Nov 2017 14:50:32 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        richard.fellner@...dent.tugraz.at, moritz.lipp@...k.tugraz.at,
        daniel.gruss@...k.tugraz.at, michael.schwarz@...k.tugraz.at,
        luto@...nel.org, torvalds@...ux-foundation.org,
        keescook@...gle.com, hughd@...gle.com, x86@...nel.org
Subject: Re: [PATCH 08/30] x86, kaiser: unmap kernel from userspace page
 tables (core patch)

On 11/20/2017 09:21 AM, Thomas Gleixner wrote:
>> +}
>> +
>>  static inline void native_set_p4d(p4d_t *p4dp, p4d_t p4d)
>>  {
>> +#if defined(CONFIG_KAISER) && !defined(CONFIG_X86_5LEVEL)
>> +	/*
>> +	 * set_pgd() does not get called when we are running
>> +	 * CONFIG_X86_5LEVEL=y.  So, just hack around it.  We
>> +	 * know here that we have a p4d but that it is really at
>> +	 * the top level of the page tables; it is really just a
>> +	 * pgd.
>> +	 */
>> +	/* Do we need to also populate the shadow p4d? */
>> +	if (is_userspace_pgd(p4dp))
>> +		native_get_shadow_p4d(p4dp)->pgd = p4d.pgd;
> native_get_shadow_p4d() is kinda confusing, as it suggest that we get the
> entry not the pointer to it. native_get_shadow_p4d_ptr() is what it
> actually wants to be, but a setter e.g. native_set_shadow...(), we also
> have set_pgd() would be more obvious I think.

How about "kernel_to_shadow_pgdp()"? ... and friends