linux-kernel - Re: [PATCH v5 03/18] wlcore: simplify/fix/optimize reg_ch_conf

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Message-ID: <87a7hxzjda.fsf@purkki.adurom.net>
Date:   Thu, 14 Mar 2019 15:16:33 +0200
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, "H Peter Anvin" <hpa@...or.com>,
        "Dave Hansen" <dave.hansen@...el.com>,
        "Paolo Bonzini" <pbonzini@...hat.com>,
        "Ashok Raj" <ashok.raj@...el.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Xiaoyao Li " <xiaoyao.li@...el.com>,
        "Michael Chan" <michael.chan@...adcom.com>,
        "Ravi V Shankar" <ravi.v.shankar@...el.com>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        "x86" <x86@...nel.org>, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v5 03/18] wlcore: simplify/fix/optimize reg_ch_conf_pending operations

Fenghua Yu <fenghua.yu@...el.com> writes:

> From: Paolo Bonzini <pbonzini@...hat.com>
>
> Bitmaps are defined on unsigned longs, so the usage of u32[2] in the
> wlcore driver is incorrect.  As noted by Peter Zijlstra, casting arrays
> to a bitmap is incorrect for big-endian architectures.
>
> When looking at it I observed that:
>
> - operations on reg_ch_conf_pending is always under the wl_lock mutex,
> so set_bit is overkill
>
> - the only case where reg_ch_conf_pending is accessed a u32 at a time is
> unnecessary too.
>
> This patch cleans up everything in this area, and changes tmp_ch_bitmap
> to have the proper alignment.
>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>

[...]

>  int wlcore_cmd_regdomain_config_locked(struct wl1271 *wl)
>  {
>  	struct wl12xx_cmd_regdomain_dfs_config *cmd = NULL;
>  	int ret = 0, i, b, ch_bit_idx;
> -	u32 tmp_ch_bitmap[2];
> +	u32 tmp_ch_bitmap[2] __aligned(sizeof(unsigned long));
>  	struct wiphy *wiphy = wl->hw->wiphy;
>  	struct ieee80211_supported_band *band;
>  	bool timeout = false;

[...]

> @@ -1754,8 +1751,8 @@ int wlcore_cmd_regdomain_config_locked(struct wl1271 *wl)
>  		goto out;
>  	}
>  
> -	cmd->ch_bit_map1 = cpu_to_le32(tmp_ch_bitmap[0]);
> -	cmd->ch_bit_map2 = cpu_to_le32(tmp_ch_bitmap[1]);
> +	cmd->ch_bit_map1 = tmp_ch_bitmap[0];
> +	cmd->ch_bit_map2 = tmp_ch_bitmap[1];

Will sparse still be happy? AFAICS you are now assigning u32 to __le32:

struct wl12xx_cmd_regdomain_dfs_config {
       struct wl1271_cmd_header header;

       __le32 ch_bit_map1;
       __le32 ch_bit_map2;

Also this doesn't depend on anything else from this patchset, right? So
I could apply this directly?

-- 
Kalle Valo