From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sipsolutions.net (s3.sipsolutions.net [168.119.38.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5A48032A3E5 for ; Fri, 24 Apr 2026 08:41:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=168.119.38.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777020076; cv=none; b=mObIX5bNs2MzYWmc44rw8cuadRrl1RkuAGIjrrxCDKt4vrl214qpxNngXfuwmlg2wTHMNGvEtDoIXG6Sghwuk8o9P9ASPwhZ3oRsSbm4lHPbWxA2ung+VFijQ6qTyDZCY44oWfYa0IN7PXD9z6NuKiQuxzgQ6ueUXBZW12KGFZk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777020076; c=relaxed/simple; bh=DKksjASOOqAqQTcMbQSn8hwSxzfGGydWIiG+EBSTjrA=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References: Content-Type:MIME-Version; b=BBPHgXXI/I/EcVOuzzbZgWI65df8wXAoybeVMRbG8wqRRPacowPKeZjAH+3Y2BBJy62ijT27yxCd/QuVmcx5WaEwQTIg8dJqA807g7ASgfEY0VgosbFTwtLnR9r41U1qAZxsKXl6rYCJsAQGs9kgvmoi5f6ajUZ1/Vc7ZoumgHo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=permerror header.from=sipsolutions.net; spf=none smtp.mailfrom=sipsolutions.net; dkim=pass (2048-bit key) header.d=sipsolutions.net header.i=@sipsolutions.net header.b=lmrY4JHU; arc=none smtp.client-ip=168.119.38.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=permerror header.from=sipsolutions.net Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=sipsolutions.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sipsolutions.net header.i=@sipsolutions.net header.b="lmrY4JHU" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sipsolutions.net; s=mail; h=MIME-Version:Content-Transfer-Encoding: Content-Type:References:In-Reply-To:Date:To:From:Subject:Message-ID:Sender: Reply-To:Cc:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-To: Resent-Cc:Resent-Message-ID; bh=DKksjASOOqAqQTcMbQSn8hwSxzfGGydWIiG+EBSTjrA=; t=1777020073; x=1778229673; b=lmrY4JHUD3+PTWzM2rJbwbdLxe9T1rQI7xc7OsOwTINbB+f WVNvahXzd5+PlNF6kR/s24x1nEIPrfZBAFD6qI9a1m9H1+LP3oCZU21uV19icZqF8tc5gKCml2n/+ N34YL7BqVFpNJ+/bDB6EdaqB8vyGyyP08oTbT8Il4chKwceTMILJ9H1Pc68qK7Os6ihbNaMKFHFxS tBycUcKTtaat1DX7YRQTPmPS36oS0xZsBg7rNpiNaP1CGYNXDb7jBPpPd1DeNGVridMmHAJA1Roqv hwuHRJIgzNR9J9rFaT9iDhG0MwTk1QJbU7Qp6TmmugAKpep2/b15b42YleSZQXLA==; Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.98.2) (envelope-from ) id 1wGC5w-000000096PK-2pvg; Fri, 24 Apr 2026 10:41:04 +0200 Message-ID: <2572d9663012ac4481d6c32aa9a4f252162c9bce.camel@sipsolutions.net> Subject: Re: mac80211 HT/VHT MCS check change causing Wi-Fi speed drop (~20 Mbps cap) on iwlwifi From: Johannes Berg To: Jayden Fowler , linux-wireless@vger.kernel.org Date: Fri, 24 Apr 2026 10:41:03 +0200 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-malware-bazaar: not-scanned On Fri, 2026-04-24 at 04:28 -0400, Jayden Fowler wrote: > Hello, >=20 > I think I=E2=80=99ve run into a regression in mac80211 that affects Wi-Fi= speeds=20 > on Intel iwlwifi (and possibly some Realtek cards too). >=20 > After testing a bunch of kernels, I noticed something pretty consistent: >=20 > Kernels with this commit Wi-Fi gets stuck around ~20 Mbps max > Kernels without it (or after removing a small part of it) speeds go back= =20 > to normal (hundreds of Mbps as expected) >=20 > The commit I bisected it to is: >=20 > 574faa0e936d12718e2cadad11ce1e184d9e5a32 > "wifi: mac80211: add HT and VHT basic set verification" >=20 > The issue seems to come from the new HT/VHT MCS verification logic. When= =20 > it runs, it sometimes decides the AP=E2=80=99s advertised rates are=20 > =E2=80=9Cunsupported=E2=80=9D and then forces a downgrade in connection m= ode/bandwidth. >=20 > That downgrade looks like it=E2=80=99s what causes the big speed drop. Yeah, there are too many AP bugs ... https://patchwork.kernel.org/project/linux-wireless/patch/99Mv9QEceyPrQhSP5= 2MtAVmz0_kWJmzqotJjD9YW6LGLqk-AZloAueUyHCURilFkuqOh6Ecv8i2KKdSE1ujP3AnbU5QE= ouVisT1w_V3xdfc=3D@r26.me/ johannes