Re: [PATCH V7 v7] virtio: introduce SUSPEND bit in device status

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Aug 13, 2024 at 06:55:04AM +0000, Parav Pandit wrote:
> That means, PCI HW needs to return suspend=0, until the device is not suspended.
> In this example, the device cannot build special circuitry to answer suspend=true within 50nsec, or in other words building special circuitry to return suspend=false is too complex for the slow operation.
> 
> If this understanding of burden is clear,
> 
> The proposal is, can you please extend the interface such that,
> 
> 1. driver writes suspend command.
> 2. driver reads suspend_status, and receives not_completed=(false). This is the default value.
> 3. When the device completes suspend, it changes the polarity of suspend_status=true.
> 
> This has two main benefits:
> [A] This will enable software-based devices to write data to slow files and does not have to force VM_EXITs.
> 
> [B] It also enables hw based devices to not build special circuitry to answer within 50nsec, which can get very complicated for tens or hundreds of PCI PFs.

I read this several times, and I don't understand what is proposed.
A special register for suspend/resume? Is this the difference?

-- 
MST