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 X-Spam-Level: X-Spam-Status: No, score=-0.3 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,HTML_MESSAGE,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6525C352A3 for ; Thu, 13 Feb 2020 19:51:43 +0000 (UTC) Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3B9B32168B for ; Thu, 13 Feb 2020 19:51:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="nOQnB5J7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B9B32168B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernelnewbies-bounces@kernelnewbies.org Received: from localhost ([::1] helo=shelob.surriel.com) by shelob.surriel.com with esmtp (Exim 4.92.3) (envelope-from ) id 1j2KW1-0006Jy-EP; Thu, 13 Feb 2020 14:51:13 -0500 Received: from mail-il1-x143.google.com ([2607:f8b0:4864:20::143]) by shelob.surriel.com with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.92.3) (envelope-from ) id 1j2KVz-0006Jo-5l for Kernelnewbies@kernelnewbies.org; Thu, 13 Feb 2020 14:51:11 -0500 Received: by mail-il1-x143.google.com with SMTP id i7so6043389ilr.7 for ; Thu, 13 Feb 2020 11:51:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=MwHI2rcJfLylLLjcpVk6RcisXIG9Z6szJv7MzGQ49pk=; b=nOQnB5J7pDn+p5+tfAAQdUpE8jWfrCYhQkUi+p9qssa14tGLpOTovAT5wl8tENhhzg IX5HSPwY6lEyBqiQ//hl78wMZFMN+i4L1Y1BgPEngs2Vu9WAkTzicfhWGnY6lzJ/zBx+ jSky0AtzPbYtZaGy2KzdKakCx2qZh6HbrF4AgCqjYNY0dVTEcW8C5X0a5iEsAS4iSnF3 m/miKc5lQPnwPlkUzucef6R0jzysxWL3Y+S/XWRF9B00XM4GxCCJB+w4P5efznbinVbI ihGvNogzlVbIlXHI4/vSpUEHK1x7BbChTYOh3n2BYJWnLq/222MWzdunDCrUklbgrZAu 0PgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=MwHI2rcJfLylLLjcpVk6RcisXIG9Z6szJv7MzGQ49pk=; b=Sxsb1Km8WpWfSrL03XrRNxi+Y0zTHsL05PHlk1y9KV21CcwE8mCGL9WUVdJCUgQAqb GT/tdAnc3OlqFitOCFP26aL3PfJlMl0pMva3BdL2/6Sco5twdPD2ZWDg8YbkXeDvCgJ1 7HK7xBQYgGMyNqfmCTpaAUFPbFzlcJKwzMRicLPZMr1VXC+Eb6bKbwxzQYWIXwKK2mUa l4W6UOm/bfY48TSpwxUID5cVxEWUNCbePMGwGBeKk1CW43LGIYIKkW6F59dA7V8x9Bx3 4KkG95eAKmBiEjDB+jOBQQZ8eaDKSWY9MAIukoURscaNDmsrWPIUvbToa4GqKaiH5qxA Np9A== X-Gm-Message-State: APjAAAW0GXQjrfcYx0wAejkuLUV4LY8ZbKU6MFJD/euOGPjXwfbLZMNJ 3k0T9OmgFg4sErsAJZ5czaMDTE6gKaFVkmGjHFE= X-Google-Smtp-Source: APXvYqzb0zusmjMx6kB0+nY81TuTPF748sAIU9tm5QocObxZAX89+mA+e3aD694glgxZ2XzFPrxa2bryHIdx+CcU3rs= X-Received: by 2002:a92:81d9:: with SMTP id q86mr16815354ilk.67.1581623463511; Thu, 13 Feb 2020 11:51:03 -0800 (PST) MIME-Version: 1.0 References: <20200213174846.GA3688355@kroah.com> In-Reply-To: <20200213174846.GA3688355@kroah.com> From: Sadanand Warrier Date: Thu, 13 Feb 2020 14:50:52 -0500 Message-ID: Subject: Re: PCIe hotplug To: Greg KH Cc: Kernelnewbies@kernelnewbies.org X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============3212472189281747425==" Errors-To: kernelnewbies-bounces@kernelnewbies.org --===============3212472189281747425== Content-Type: multipart/alternative; boundary="000000000000b60a94059e7a6807" --000000000000b60a94059e7a6807 Content-Type: text/plain; charset="UTF-8" Thank you Greg. About the last one , it's been a while but I wasn't sure whether Linux was going to do its own enumeration. Of course it's best to take advantage of all the stuff done by UEFI , padding etc. S On Thu, 13 Feb 2020 at 12:48, Greg KH wrote: > On Thu, Feb 13, 2020 at 12:40:59PM -0500, Sadanand Warrier wrote: > > Hi > > I had question about PCIe hotplug. We have hardware that is connected > > to the host by means of two PCIe switches. i.e. the host sees a PCIe > switch > > connected to one of its buses and on the far side of that switch another > > PCIe switch which has a PCIe device. > > It is possible that this device does not train its host facing PCIe > > links before the server enumerates down its PCI bus and reaches those > > links. It is also possible the PCIe switch to which the device is > attached > > has not been able to train its own links before server enumeration. > > Is PCIe hotplug built to work on schemes like this? Let us assume that > > the hardware has been designed to trasmit a presence signal once the > links > > are trained but this could happen after the server enumeration? > > Look at the PCIe hotplug spec, it should answer all of your questions > about this. > > > Incidentally does the server take advantage of the BIOS/UEFI > enumeration? > > Yes, of course, how else would the kernel be able to enumerate PCI > devices? :) > > thanks, > > greg k-h > --000000000000b60a94059e7a6807 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Thank you Greg.
About the last one , it'= ;s been a while but I wasn't sure whether Linux was going to do its own= enumeration.
Of course it's best to take advantage of all th= e stuff done by UEFI , padding etc.

S

On Thu, 13 Fe= b 2020 at 12:48, Greg KH <greg@kroah.c= om> wrote: