From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=citrix.com header.i=@citrix.com header.b="RwJFtWCL" Received: from mail-wr1-x42d.google.com (mail-wr1-x42d.google.com [IPv6:2a00:1450:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5255810A for ; Thu, 14 Dec 2023 00:46:55 -0800 (PST) Received: by mail-wr1-x42d.google.com with SMTP id ffacd0b85a97d-33644eeb305so498517f8f.1 for ; Thu, 14 Dec 2023 00:46:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1702543614; x=1703148414; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=VRbI5kjcIRPl4oUV94OH4S0caT5wjSRkLPGI8s4DA/k=; b=RwJFtWCLy6gKQ1XreFMJ1I3Ovx1KH6yNtx1r1pjcsEMbwfqbNJexuq4vW1ozGRym7H umAIlnkQgdA2st58ieNO/4Wznc3+zJZXYgHk3tDOcV43qrU27LOybN5gCzIs1Sfl0J9L btHXh70U2LPzrJ2R88fK3ZwbxR+wQ6rBuXuI4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702543614; x=1703148414; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=VRbI5kjcIRPl4oUV94OH4S0caT5wjSRkLPGI8s4DA/k=; b=NjzglmNa+yh2X8cBXzGPuAe2C3Bf+Ofa84CmHEbaS/vWa/tUbuqMdNfs2rXvrS/8uI 4pcqa/poildeUtUrHDn7bjTBwLIF+T4GEulhr3QvlV0AvkyvVlHITke+7VP7S+eIkKxd IIYfdwNnidJrZXSefVmi3YY9UUOdYYaM7Qj+6SrvStaoRuXUXzuonsDJlpRGSx2tJ4vy 7xt8Hsoh2l2T+JNqXkxZmD22yYctMqeHHDdQyjiN2eCnwDb5+oGjvXDVbkXH7C3++Ip5 D5X0RoRAdS9tW2PmTlNMy6p/K+0DMPF/zVAdyzNdjvKyUDiQSMQEsKlgYaTfMJDX5cY+ ptUQ== X-Gm-Message-State: AOJu0YwTamzFoI/9o93eeI57sCMtZFEiuY5gjNV/9T4iTM9u2Rve/fOC r/10KOOd4J/zkDg5RYYvapo65Q== X-Google-Smtp-Source: AGHT+IFs1KY+zsQXwuAqC03LiFJwO3hRSTw+6+YdEzAfW15eHnWqW0A0/g+qvKOg7kFPUNaNrf5hAQ== X-Received: by 2002:a5d:6aca:0:b0:336:9ec:d613 with SMTP id u10-20020a5d6aca000000b0033609ecd613mr6133406wrw.90.1702543613756; Thu, 14 Dec 2023 00:46:53 -0800 (PST) Received: from localhost ([213.195.127.70]) by smtp.gmail.com with ESMTPSA id h12-20020a5d504c000000b003333521a1cesm3283381wrt.57.2023.12.14.00.46.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Dec 2023 00:46:53 -0800 (PST) Date: Thu, 14 Dec 2023 09:46:52 +0100 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: "Chen, Jiqian" Cc: "Rafael J . Wysocki" , Len Brown , Bjorn Helgaas , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-acpi@vger.kernel.org" , "xen-devel@lists.xenproject.org" , "Deucher, Alexander" , "Koenig, Christian" , "Huang, Ray" Subject: Re: [RFC KERNEL PATCH v3 3/3] PCI/sysfs: Add gsi sysfs for pci_dev Message-ID: References: <20231210161519.1550860-1-Jiqian.Chen@amd.com> <20231210161519.1550860-4-Jiqian.Chen@amd.com> Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Dec 14, 2023 at 07:08:32AM +0000, Chen, Jiqian wrote: > On 2023/12/13 20:12, Roger Pau Monné wrote: > > On Wed, Dec 13, 2023 at 03:31:21AM +0000, Chen, Jiqian wrote: > >> On 2023/12/12 17:18, Roger Pau Monné wrote: > >>> On Tue, Dec 12, 2023 at 06:34:27AM +0000, Chen, Jiqian wrote: > >>>> > >>>> On 2023/12/12 01:57, Roger Pau Monné wrote: > >>>>> On Mon, Dec 11, 2023 at 12:15:19AM +0800, Jiqian Chen wrote: > >>>>>> There is a need for some scenarios to use gsi sysfs. > >>>>>> For example, when xen passthrough a device to dumU, it will > >>>>>> use gsi to map pirq, but currently userspace can't get gsi > >>>>>> number. > >>>>>> So, add gsi sysfs for that and for other potential scenarios. > >>>>>> > >>>>>> Co-developed-by: Huang Rui > >>>>>> Signed-off-by: Jiqian Chen > >>>>>> --- > >>>>>> drivers/acpi/pci_irq.c | 1 + > >>>>>> drivers/pci/pci-sysfs.c | 11 +++++++++++ > >>>>>> include/linux/pci.h | 2 ++ > >>>>>> 3 files changed, 14 insertions(+) > >>>>>> > >>>>>> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c > >>>>>> index 630fe0a34bc6..739a58755df2 100644 > >>>>>> --- a/drivers/acpi/pci_irq.c > >>>>>> +++ b/drivers/acpi/pci_irq.c > >>>>>> @@ -449,6 +449,7 @@ int acpi_pci_irq_enable(struct pci_dev *dev) > >>>>>> kfree(entry); > >>>>>> return 0; > >>>>>> } > >>>>>> + dev->gsi = gsi; > >>>>> > >>>>> It would be better if the gsi if fetched without requiring calling > >>>>> acpi_pci_irq_enable(), as the gsi doesn't require the interrupt to be > >>>>> enabled. The gsi is known at boot time and won't change for the > >>>>> lifetime of the device. > >>>> Do you have any suggest places to do this? > >>> > >>> I'm not an expert on this, but drivers/pci/pci-sysfs.c would seem like > >>> a better place, together with the rest of the resources. > >> I'm not familiar with this too. But it seems pci-sysfs.c only creates sysfs node and supports the read/write method without initializing the values. > >> If want to initialize the value of gsi here. An approach to initialize it is to call acpi_pci_irq_lookup to get gsi number when the first time it is read? > > > > Hm, maybe, I don't really have much experience with sysfs, so don't > > know how nodes are usually initialized. > Maybe the maintainers of sysfs can give some suggest places to initialize the value of gsi. > > > > >>> > >>> Maybe my understanding is incorrect, but given the suggested placement > >>> in acpi_pci_irq_enable() I think the device would need to bind the > >>> interrupt in order for the gsi node to appear on sysfs? > >> No, gsi sysfs has existed there, in acpi_pci_irq_enable is to initialize the value of gsi. > >> > >>> > >>> Would the current approach work if the device is assigned to pciback > >>> on the kernel command line, and thus never owned by any driver in > >>> dom0? > >> If assigned to pciback, I think pciback will enable the device, and then acpi_pci_irq_enable will be called, and then the gsi will be initialized. So, current can work. > > > > This needs checking to be sure, I'm certainly not that familiar. You > > would need to at least test that it works properly when the device is > > hidden using xen-pciback.hide=(SBDF) in the Linux kernel command line. > Sure, I have validated it on my side. Both the "Static assignment for built-in xen-pciback(xen-pciback.hide=(SBDF))" and the "Dynamic assignment with xl(sudo modprobe xen-pciback & sudo xl pci-assignable-add SBDF)" can work fine with current implementation. Oh, OK, if that's the case I don't have much objection in doing the initialization in acpi_pci_irq_enable(), that's an internal Linux detail. I mostly care about the GSI being exposed in sysfs in a non-Xen specific way. Thanks, Roger.