From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [RFC/PATCH 1/1] virtio: Introduce MMIO ops Date: Thu, 30 Apr 2020 11:14:32 +0100 Message-ID: <20200430101431.GD19932@willie-the-truck> References: <1588240976-10213-1-git-send-email-vatsa@codeaurora.org> <1588240976-10213-2-git-send-email-vatsa@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1588240976-10213-2-git-send-email-vatsa@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org To: Srivatsa Vaddagiri Cc: konrad.wilk@oracle.com, mst@redhat.com, jasowang@redhat.com, jan.kiszka@siemens.com, stefano.stabellini@xilinx.com, iommu@lists.linux-foundation.org, virtualization@lists.linux-foundation.org, virtio-dev@lists.oasis-open.org, tsoni@codeaurora.org, pratikp@codeaurora.org, christoffer.dall@arm.com, alex.bennee@linaro.org, linux-kernel@vger.kernel.org List-Id: virtualization@lists.linuxfoundation.org On Thu, Apr 30, 2020 at 03:32:56PM +0530, Srivatsa Vaddagiri wrote: > Some hypervisors may not support MMIO transport i.e trap config > space access and have it be handled by backend driver. They may > allow other ways to interact with backend such as message-queue > or doorbell API. This patch allows for hypervisor specific > methods for config space IO. > > Signed-off-by: Srivatsa Vaddagiri > --- > drivers/virtio/virtio_mmio.c | 131 ++++++++++++++++++++++++++----------------- > include/linux/virtio.h | 14 +++++ > 2 files changed, 94 insertions(+), 51 deletions(-) > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > index 97d5725..69bfa35 100644 > --- a/drivers/virtio/virtio_mmio.c > +++ b/drivers/virtio/virtio_mmio.c > @@ -100,7 +100,35 @@ struct virtio_mmio_vq_info { > struct list_head node; > }; > > +#ifdef CONFIG_VIRTIO_MMIO_OPS > > +static struct virtio_mmio_ops *mmio_ops; > + > +#define virtio_readb(a) mmio_ops->mmio_readl((a)) > +#define virtio_readw(a) mmio_ops->mmio_readl((a)) > +#define virtio_readl(a) mmio_ops->mmio_readl((a)) > +#define virtio_writeb(val, a) mmio_ops->mmio_writeb((val), (a)) > +#define virtio_writew(val, a) mmio_ops->mmio_writew((val), (a)) > +#define virtio_writel(val, a) mmio_ops->mmio_writel((val), (a)) How exactly are these ops hooked up? I'm envisaging something like: ops = spec_compliant_ops; [...] if (firmware_says_hypervisor_is_buggy()) ops = magic_qcom_ops; am I wrong? > +int register_virtio_mmio_ops(struct virtio_mmio_ops *ops) > +{ > + pr_info("Registered %s as mmio ops\n", ops->name); > + mmio_ops = ops; Not looking good, and really defeats the point of standardising this stuff imo. Will