Re: [PATCH 0/2] PCI/P2PDMA: Allow P2PDMA in VMware and Hyper-V guests on Intel hosts

[Bjorn Helgaas]

On Fri, Oct 09, 2026 at 08:40:32AM -0700, Pavel Popov wrote:
> VMware and Hyper-V expose passthrough devices to guest VMs without an
> explicit host bridge device. Consequently, host_bridge_whitelist()
> cannot automatically identify the underlying host bridge structure,
> causing Peer-to-Peer DMA (P2PDMA) requests to be rejected unless the
> device IDs are explicitly listed in pci_p2pdma_whitelist[]. To enable
> P2PDMA support in virtualized environments on Intel hosts, this series
> introduces hypervisor_supports_p2pdma().
> 
> Although alternative P2PDMA mechanisms are in development [1], their
> adoption timeline in hypervisors remains uncertain. This solution
> addresses the immediate need to support both new and existing
> hypervisor deployments.
> 
> The patches are organized by hypervisor for clarity. While the primary
> focus is VMware, a corresponding Hyper-V patch addresses the same
> pattern and is included for maintainer consideration.
> 
> [1] https://lore.kernel.org/r/20260812-hmat-p2p-v1-0-75ac41380585@xxxxxxxxxx
> 
> Pavel Popov (2):
>   PCI/P2PDMA: Allow P2PDMA in VMware guests on Intel hosts
>   PCI/P2PDMA: Allow P2PDMA in Hyper-V guests on Intel hosts
> 
>  drivers/pci/p2pdma.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)

Applied with the #ifdef tweak Logan suggested to pci/p2pdma for v7.4,
thanks!

FWIW, it's better if responses like Jim's Reviewed-by actually appear
on the mailing list.  I don't see anything in lore, so I assume it
must have been private review.