linux-kernel - Re: [PATCH v4 09/12] x86/mtrr: construct a memory map with cache modes

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Message-ID: <20230331125740.GCZCbYxFkJOg8hIl6C@fat_crate.local>
Date:   Fri, 31 Mar 2023 14:57:40 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Juergen Gross <jgross@...e.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v4 09/12] x86/mtrr: construct a memory map with cache
 modes

On Mon, Mar 06, 2023 at 05:34:22PM +0100, Juergen Gross wrote:
> +/* Build the cache_map containing the cache modes per memory range. */
> +void mtrr_build_map(void)
> +{
> +	unsigned int i;
> +	u64 start, end, size;
> +	u8 type;
> +
> +	if (!mtrr_state.enabled)
	     ^^^^^^^^^^^^^^^^^^^

> +		return;
> +
> +	/* Add fixed MTRRs, optimize for adjacent entries with same type. */
> +	if (mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED) {
	    ^^^^^^^^^^^^^^^^^^

First check can go.

> +		start = 0;
> +		end = size = 0x10000;
> +		type = mtrr_state.fixed_ranges[0];
> +
> +		for (i = 1; i < MTRR_NUM_FIXED_RANGES; i++) {

Loops starts at 1. Comment explaining why pls.

> +			if (i == 8 || i == 24)

Magic numbers.

Ok, I'll stop here.

Please send a new version with the review comments incorporated. I need
to look more at that map thing more.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette