Re: [PATCH v2 08/14] x86: Replace MTRR_* constants with X86_MT_* constants

From: Jan Beulich <jbeulich@suse.com>
To: Demi Marie Obenour <demi@invisiblethingslab.com>
Cc: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>, "Wei Liu" <wl@xen.org>,
	"Jun Nakajima" <jun.nakajima@intel.com>,
	"Kevin Tian" <kevin.tian@intel.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Tim Deegan" <tim@xen.org>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v2 08/14] x86: Replace MTRR_* constants with X86_MT_* constants
Date: Wed, 14 Dec 2022 12:54:17 +0100	[thread overview]
Message-ID: <933cd359-7b79-0261-825c-2b5ca1c7a917@suse.com> (raw)
In-Reply-To: <fec68f62fcea8fe7f6cf6e7963ea4c6b30ea5166.1670948141.git.demi@invisiblethingslab.com>

On 13.12.2022 23:26, Demi Marie Obenour wrote:
> This allows eliminating most of the former.  No functional change
> intended.

"most" would be nice to accompany by what has to stay, and for what reason.
Is this solely about MTRR_NUM_TYPES or more?

> --- a/xen/arch/x86/include/asm/mtrr.h
> +++ b/xen/arch/x86/include/asm/mtrr.h
> @@ -3,12 +3,6 @@
>  
>  #include <xen/mm.h>
>  
> -/* These are the region types. They match the architectural specification. */
> -#define MTRR_TYPE_UNCACHABLE 0
> -#define MTRR_TYPE_WRCOMB     1
> -#define MTRR_TYPE_WRTHROUGH  4
> -#define MTRR_TYPE_WRPROT     5
> -#define MTRR_TYPE_WRBACK     6
>  #define MTRR_NUM_TYPES       7

May I suggest to use X86_MT_UCM here, matching the transformation you
do ...

> @@ -1426,12 +1426,12 @@ void ept_p2m_uninit(struct p2m_domain *p2m)
>  static const char *memory_type_to_str(unsigned int x)
>  {
>      static const char memory_types[8][3] = {
> -        [MTRR_TYPE_UNCACHABLE]     = "UC",
> -        [MTRR_TYPE_WRCOMB]         = "WC",
> -        [MTRR_TYPE_WRTHROUGH]      = "WT",
> -        [MTRR_TYPE_WRPROT]         = "WP",
> -        [MTRR_TYPE_WRBACK]         = "WB",
> -        [MTRR_NUM_TYPES]           = "??"
> +        [X86_MT_UC]  = "UC",
> +        [X86_MT_WC]  = "WC",
> +        [X86_MT_WT]  = "WT",
> +        [X86_MT_WP]  = "WP",
> +        [X86_MT_WB]  = "WB",
> +        [X86_MT_UCM] = "??",

... here (and where I wonder whether MTRR_NUM_TYPES wouldn't better be
kept).

Jan