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From: Srivatsa Vaddagiri <vatsa@codeaurora.org>
To: Will Deacon <will@kernel.org>
Cc: tsoni@codeaurora.org, virtio-dev@lists.oasis-open.org,
	mst@redhat.com, jan.kiszka@siemens.com, jasowang@redhat.com,
	konrad.wilk@oracle.com, christoffer.dall@arm.com,
	virtualization@lists.linux-foundation.org,
	alex.bennee@linaro.org, iommu@lists.linux-foundation.org,
	stefano.stabellini@xilinx.com, pratikp@codeaurora.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC/PATCH 1/1] virtio: Introduce MMIO ops
Date: Thu, 30 Apr 2020 16:04:46 +0530	[thread overview]
Message-ID: <20200430103446.GH5097@quicinc.com> (raw)
In-Reply-To: <20200430101431.GD19932@willie-the-truck>

* Will Deacon <will@kernel.org> [2020-04-30 11:14:32]:

> > +#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?

If CONFIG_VIRTIO_MMIO_OPS is defined, then I expect this to be unconditionally
set to 'magic_qcom_ops' that uses hypervisor-supported interface for IO (for
example: message_queue_send() and message_queue_recevie() hypercalls).

> > +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.

Ok. I guess the other option is to standardize on a new virtio transport (like
ivshmem2-virtio)?

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Srivatsa Vaddagiri <vatsa@codeaurora.org>
To: Will Deacon <will@kernel.org>
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
Subject: Re: [RFC/PATCH 1/1] virtio: Introduce MMIO ops
Date: Thu, 30 Apr 2020 16:04:46 +0530	[thread overview]
Message-ID: <20200430103446.GH5097@quicinc.com> (raw)
In-Reply-To: <20200430101431.GD19932@willie-the-truck>

* Will Deacon <will@kernel.org> [2020-04-30 11:14:32]:

> > +#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?

If CONFIG_VIRTIO_MMIO_OPS is defined, then I expect this to be unconditionally
set to 'magic_qcom_ops' that uses hypervisor-supported interface for IO (for
example: message_queue_send() and message_queue_recevie() hypercalls).

> > +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.

Ok. I guess the other option is to standardize on a new virtio transport (like
ivshmem2-virtio)?

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

  reply	other threads:[~2020-04-30 10:35 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-30 10:02 [RFC/PATCH 0/1] virtio_mmio: hypervisor specific interfaces for MMIO Srivatsa Vaddagiri
2020-04-30 10:02 ` Srivatsa Vaddagiri
2020-04-30 10:02 ` [RFC/PATCH 1/1] virtio: Introduce MMIO ops Srivatsa Vaddagiri
2020-04-30 10:02   ` Srivatsa Vaddagiri
2020-04-30 10:14   ` Will Deacon
2020-04-30 10:14     ` Will Deacon
2020-04-30 10:34     ` Srivatsa Vaddagiri [this message]
2020-04-30 10:34       ` Srivatsa Vaddagiri
2020-04-30 10:41       ` Will Deacon
2020-04-30 10:41         ` Will Deacon
2020-04-30 11:11         ` Srivatsa Vaddagiri
2020-04-30 11:11           ` Srivatsa Vaddagiri
2020-04-30 12:59           ` Jan Kiszka
2020-04-30 12:59             ` Jan Kiszka
2020-04-30 12:59             ` [virtio-dev] " Jan Kiszka
2020-04-30 13:33             ` Srivatsa Vaddagiri
2020-04-30 13:33               ` Srivatsa Vaddagiri
2020-04-30 13:33               ` Srivatsa Vaddagiri
2020-04-30 19:34               ` Michael S. Tsirkin
2020-04-30 19:34                 ` Michael S. Tsirkin
2020-04-30 19:34                 ` [virtio-dev] " Michael S. Tsirkin
2020-04-30 10:07 ` [RFC/PATCH 0/1] virtio_mmio: hypervisor specific interfaces for MMIO Michael S. Tsirkin
2020-04-30 10:07   ` Michael S. Tsirkin
2020-04-30 10:07   ` [virtio-dev] " Michael S. Tsirkin
2020-04-30 10:40   ` Srivatsa Vaddagiri
2020-04-30 10:40     ` Srivatsa Vaddagiri
2020-04-30 10:56   ` Jason Wang
2020-04-30 10:56     ` Jason Wang
2020-04-30 10:56     ` [virtio-dev] " Jason Wang
2020-04-30 10:08 ` Will Deacon
2020-04-30 10:08   ` Will Deacon
2020-04-30 10:29   ` Srivatsa Vaddagiri
2020-04-30 10:29     ` Srivatsa Vaddagiri
2020-04-30 10:39     ` Will Deacon
2020-04-30 10:39       ` Will Deacon
2020-04-30 11:02       ` Srivatsa Vaddagiri
2020-04-30 11:02         ` Srivatsa Vaddagiri
2020-04-30 11:02         ` Srivatsa Vaddagiri

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