From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (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 D541237719 for ; Tue, 16 Apr 2024 16:59:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713286781; cv=none; b=Jt43gGMoHU2DEKV+1HVF/2eJSAbL+Ffs4U9S1l+X4BECLKNwy66y3j5ks1M7e5EJu1ipIBEkUtOngd2vW/khRouq8dcD7bXGl8ic7EpolF9M2aUxpJ5PAYrSxXBSLx/uHUtCPbmAjhpIvROlRHXOmzKsPtGcyX//uwo75lQtoV8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713286781; c=relaxed/simple; bh=OqwfRgfuRz/ivsxvdcUz3wpO0OSe7tdZKPZ6/JVHlZE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bkzzrxzKlXZyj5YwAfh0p6Aq+ggHBSD4wGJ96ygbMNYHNEXkO3A22ybETsepSfFNUANnVaFUzzsNKe6E5T9a5GjJiQHw24os2npTv3M4LCgDBvz5RXpDS8S8LuA6yn7cIUirh6aoQIkmZoCqBgqmvp5IMBmmePJFm/wWHyrkGbc= ARC-Authentication-Results:i=1; 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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ENzBJ5yxGnQURnAwcjuAXE1UBTEskLookeB5f6Tgc+7D/raTOPxJRpt0p8BWYzBfG 4/Lr2fbCxsUtFelRRx5nbISu5vcnk+z5KUzBAJBbPNHSuyBSxdeQcRPZNdm/krQbNt +OPHnAa0hrnV0xkqU7+pOhgGsDz7Tz1YqXp3EVA1YNmBPsuMEM37HDH2CW8TnsP1wh v8Wd6Ylj4b9wtIah1xfIslFN5VfyPJ5jinY/yP2eewa4aiOpQB9S+TRPkRpGSEvs7f GwvwOQMB7m4cp67I1Vklxr/pkkFOeLupEeKtNZyzmG8CMxHeAYEhhN7zAzgYFN8oLg 9X2c5nJ3Fg/aw== Message-ID: Date: Tue, 16 Apr 2024 09:58:45 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/1] x86/fred: Fix int80 emulation for FRED To: Borislav Petkov Cc: linux-kernel@vger.kernel.org, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com References: <20240412234058.1106744-1-xin@zytor.com> <20240416101147.GDZh5O473e4X_ZG1lZ@fat_crate.local> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/16/2024 3:11 AM, Borislav Petkov wrote: > On Fri, Apr 12, 2024 at 04:40:58PM -0700, Xin Li (Intel) wrote: >> Commit 55617fb991df > > Use the full commit abbreviation when mentioning commits: > > "Commit > > 55617fb991df ("x86/entry: Do not allow external 0x80 interrupts") > > .." oh, I should have done it! > >> added a bunch of tests to the int $0x80 path, > > Added a bunch of tests? > 'checks' might be a better term to use? > What does that even mean? > >> however they are unnecessary and event wrong in fact under FRED. > > Are the bunch of tests wrong or is do_int80_emulation() simply the wrong > handler to use on a FRED? I think the explanations are below, and you saw it a bit later. BTW, comments are added around the code changes. > >> First FRED distinguishes external interrupts from software interrupts, >> thus int80_emulation() should NEVER be called for handling an external >> interrupt, and then int80_is_external() should be skipped under FRED. >> >> Second, the FRED kernel entry handler NEVER dispatches INTx, which is >> of event type EVENT_TYPE_SWINT, so the user mode checking in >> do_int80_emulation() is redundant, and should be skipped. >> >> It might be even better to strip down do_int80_emulation() to a lean >> fred_int80_emulation(), not to mention int80_emulation() does a >> CLEAR_BRANCH_HISTORY. > > Yah, how about you do a FRED-specific INT80 handler instead of > sprinkling moar tests around? fred_intx() looks like the right place to > stuff it in... > I will add fred_int80_emulation(), which duplicates a big part of do_int80_emulation(), however this seems more readable. Thanks! Xin