Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 11 Nov 2022 13:18:32 -0800
From:   Davidlohr Bueso <dave@stgolabs.net>
To:     Ira Weiny <ira.weiny@intel.com>
Cc:     Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Bjorn Helgaas <helgaas@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>, dave.jiang@intel.com,
        alison.schofield@intel.com, bwidawsk@kernel.org,
        vishal.l.verma@intel.com, a.manzanares@samsung.com,
        linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org,
        Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/2] cxl/pci: Add generic MSI-X/MSI irq support
Message-ID: <20221111211832.zfjtehrk4fhjcjea@offworld>
References: <20221024133633.00000467@huawei.com>
 <20221025232535.GA579167@bhelgaas>
 <20221102171524.thsz2kwtirhxn7ee@offworld>
 <Y2MAdaCES+aUc2QH@iweiny-desk3>
 <20221103001833.n2gsoflnji3pcsfr@offworld>
 <20221103180916.00000bae@Huawei.com>
 <Y2xwbYEKKc9KXUDy@iweiny-desk3>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Disposition: inline
In-Reply-To: <Y2xwbYEKKc9KXUDy@iweiny-desk3>
User-Agent: NeoMutt/20220429
Precedence: bulk

On Wed, 09 Nov 2022, Ira Weiny wrote:

>Unfortunately the following does not work with the current Qemu.
>
>/*
> * NOTE: Currently all the functions which are enabled for CXL require their
> * vectors to be in the first 16.  Allocate this number as the min/max.
> */
>#define CXL_PCI_REQUIRED_VECTORS 16
>
>...
>
>        rc = pci_alloc_irq_vectors(pdev, CXL_PCI_REQUIRED_VECTORS,
>                                   CXL_PCI_REQUIRED_VECTORS,
>                                   PCI_IRQ_MSIX | PCI_IRQ_MSI);
>
>This is because Qemu CXL devices only support (with the event changes I have
>made) 8 msg numbers.  So the code fails to allocate any vectors.
>
>I guess I should have known better.  But allocating something less than 16 I
>guess needs to be allowed.
>
>But that also means that beyond knowing _if_ irq's have been enabled I think
>each CXL feature needs to know the number of vectors allocated so they can
>ensure their msg numbers are going to work.
>
>So how about the following as a diff to this patch?
>
>In the event code I have then used the nr_irq_vecs field to determine if I
>should enable the irq for each log.
>
>If you are ok with it I'm going to squash it into your patch and send out a new
>version of the event log series.

LGTM, thanks.