From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 055D2C77B7D for ; Tue, 18 Apr 2023 15:19:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231272AbjDRPTJ (ORCPT ); Tue, 18 Apr 2023 11:19:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230454AbjDRPTH (ORCPT ); Tue, 18 Apr 2023 11:19:07 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 71FE0118D3 for ; Tue, 18 Apr 2023 08:19:02 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id f66-20020a255145000000b00b7f75c3cafdso11391093ybb.16 for ; Tue, 18 Apr 2023 08:19:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1681831141; x=1684423141; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=7MmhDtuqEjzktXZMZUjTd5/IRF+IYVg/to26fXE0GgA=; b=cXwIKIbKcePgE0q1ohaCKDZjHkJcA4ZV0ksHYDn//I4wmobuvoBzNsVE0c5gNwcOTo qfw6MfVqURVUymOpmFD/viT8NRh+/QPqkWGEP/zZC6JAcCptnls0LrnevKyEF9kelJ7S srbQuo+GMmO8LJnlvFoQmWfdUkTjc8FC4m5lkUQlme08GLiW6DAKOYmxR0yi50X4h+qv h8By7Kfva1zzmByAJbHa/Mytmh7tykK5D/Pel80uXRpiw8cLZsffNvZIqTuZC8MRYm2J 7vneSyP+Ito5NYrvaeBljLBKmrP/DymNuxovYVToho1y7CNqmZEUY0dyY3rMDWtKG2kh AQXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681831141; x=1684423141; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=7MmhDtuqEjzktXZMZUjTd5/IRF+IYVg/to26fXE0GgA=; b=Ax8J1F/GYeCIezUeAls8W1P9gSbP/l99ltfWHrgmOd4X7wKEr7f0tiWLoq03Tj4D2e 9X/pBglKa6tdXgaOtkGGbHDxjc1+u2Wj2lno/tXAfPUZOCwWJriHjzL0+r+/aMnzj254 p1p0ZrWEaPtTTntAS+DwFiwfjgJ6FVQWmW++TIqLIWOcSC3W/ryZ/QnyeTAUE4KAtnb0 uDaYIF/UG9k4InXfakJIBZP8w0cAJEjZAXLsuR6Crdh6+s4t4XcvNbYEStWU823G2UtC MYDqfad0JcKkwXBHsoe14drARsF0bXLYxK6+TP5ArMgRQ7Qk7Dogf120uJe7JIjtudqK wfJg== X-Gm-Message-State: AAQBX9fFBUi1DnUJ0Yv2WWAxmNHXaoDnIZ/O0sNVPWxGF5U3+GsC9Wk/ HCccxeKFytwPoY2zUZpjSG+XrhJxlx4= X-Google-Smtp-Source: AKy350Y+AP5rglL+RyREvKohVZkyrZn94gtw9e/Bj39GeBvGlorG7JZnxzCrYv3zUY1rwsaF5NPi9Vbvcww= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:d651:0:b0:b95:f0de:240e with SMTP id n78-20020a25d651000000b00b95f0de240emr560829ybg.11.1681831141681; Tue, 18 Apr 2023 08:19:01 -0700 (PDT) Date: Tue, 18 Apr 2023 08:19:00 -0700 In-Reply-To: <20230418104743.842683-3-alexjlzheng@tencent.com> Mime-Version: 1.0 References: <20230418104743.842683-1-alexjlzheng@tencent.com> <20230418104743.842683-3-alexjlzheng@tencent.com> Message-ID: Subject: Re: [PATCH 2/2] KVM: x86: Adjust return value of pic_poll_read() From: Sean Christopherson To: alexjlzheng@gmail.com Cc: pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jinliang Zheng Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 18, 2023, alexjlzheng@gmail.com wrote: > From: Jinliang Zheng > > Returning 0x07 raises ambiguity when no interrupt is in pic_poll_read(). > Although it will not cause a functional exception (Bit 7 is 0 means no >From KVM's perspective, it's a functional change. It _shouldn't_ impact the overall functionality of the guest, but we have no idea what guest code exists in the wild. > interrupt), it will easily make developers mistakenly think that a > spurious interrupt (IRQ 7) has been returned. > > Return 0x00 instread of 0x07. Again, I do not want to introduce a functional change in this code without evidence that the change fixes something for a real world guest. Based on your response[*], that is not the case. A comment explaining the KVM behavior would be very welcome, but I'm not taking this patch. [*] https://lore.kernel.org/all/20230418075923.752113-1-alexjlzheng@tencent.com