RE: [RFC PATCH 5/5] hw/arm/virt-acpi-build: Add IORT RMR regions to handle MSI nested binding

Thu, 14 Nov 2024 01:06:17 -0800 


> -----Original Message-----
> From: Nicolin Chen <[email protected]>
> Sent: Wednesday, November 13, 2024 6:31 PM
> To: Shameerali Kolothum Thodi <[email protected]>
> Cc: [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; Linuxarm <[email protected]>; Wangzhou (B)
> <[email protected]>; jiangkunkun <[email protected]>;
> Jonathan Cameron <[email protected]>;
> [email protected]
> Subject: Re: [RFC PATCH 5/5] hw/arm/virt-acpi-build: Add IORT RMR regions
> to handle MSI nested binding
> 
> On Fri, Nov 08, 2024 at 12:52:42PM +0000, Shameer Kolothum wrote:
> > From: Eric Auger <[email protected]>
> >
> > To handle SMMUv3 nested stage support it is practical to expose the
> > guest with reserved memory regions (RMRs) covering the IOVAs used by
> > the host kernel to map physical MSI doorbells.
> 
> There has been an ongoing solution for MSI alternative:
> https://lore.kernel.org/kvm/[email protected]/
> 
> So, I think we should keep this patch out of this series, instead put it on 
> top
> of the testing branch.

Yes. I think then we can support DT solution as well. 

On that MSI RFC above, have you seen Eric's earlier/initial proposal to bind 
the Guest MSI in
nested cases. IIRC, it was providing an IOCTL and then creating a mapping in 
the host.

I think this is the latest on that.
https://lore.kernel.org/linux-iommu/[email protected]/

But not sure, why we then moved to RMR approach. Eric?

Thanks,
Shameer























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