linux-kernel - Re: [PATCH v3 1/2] x86/cpu/intel: Fix MTRR verification for TME enabled platforms

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Message-ID: <00392c722e65c8d0da40384eecf8955be4875969.camel@intel.com>
Date:   Fri, 29 Sep 2023 09:14:00 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "mingo@...nel.org" <mingo@...nel.org>,
        "Li, Xin3" <xin3.li@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Compostella, Jeremy" <jeremy.compostella@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>
Subject: Re: [PATCH v3 1/2] x86/cpu/intel: Fix MTRR verification for TME
 enabled platforms

On Thu, 2023-09-28 at 15:30 -0700, Compostella, Jeremy wrote:
> On TME enabled platform, BIOS publishes MTRR taking into account Total
> Memory Encryption (TME) reserved bits.
> 
> generic_get_mtrr() performs a sanity check of the MTRRs relying on the
> `phys_hi_rsvd' variable which is set using the cpuinfo_x86 structure
> `x86_phys_bits' field.  But at the time the generic_get_mtrr()
> function is ran the `x86_phys_bits' has not been updated by
> detect_tme() when TME is enabled.
> 
> Since the x86_phys_bits does not reflect yet the real maximal physical
> address size yet generic_get_mtrr() complains by logging the following
> messages.
> 
>     mtrr: your BIOS has configured an incorrect mask, fixing it.
>     mtrr: your BIOS has configured an incorrect mask, fixing it.
>     [...]
> 
> In such a situation, generic_get_mtrr() returns an incorrect size but
> no side effect were observed during our testing.
> 
> For `x86_phys_bits' to be updated before generic_get_mtrr() runs,
> move the detect_tme() call from init_intel() to early_init_intel().

Hi,

This move looks good to me, but +Kirill who is the author of detect_tme() for
further comments.

Also I am not sure whether it's worth to consider to move this to
get_cpu_address_sizes(), which calculates the virtual/physical address sizes. 
Thus it seems anything that can impact physical address size could be put there.

Perhaps can be done in the future if ever needed.

> 
> Change for v3:
> Take review commit message comments into account.
> 
> Change for v2:
> Add a comment in the code explaining why detect_tme() needs to called
> in early_init_intel().

You can put version history to 

	<Your SoB>
	---
	version history
	---
	...

then it will be stripped away when the patch is applied.

Also, for related multiple patches please use --cover-letter --thread to make it
a series.  You can also use --base=auto to include the base commit id to the
patch.