Re: [PATCH v4 0/2] PCI/P2PDMA: Allow P2PDMA on Intel Xeon server CPUs

[Leon Romanovsky <leon@kernel.org>]

On Wed, Nov 11, 2026 at 03:48:07AM +0000, Popov, Pavel E wrote:
> Hi Bjorn,
> 
> Gentle ping on this series. Is this OK for v7.5?

I would say no. An Intel employee was asked to clean up an Intel-created
mess while upstreaming an Intel-specific patch.

Peer-to-peer is a general concept, and the code should reflect that. It is
reasonable to expect you to join the effort and help clean it up.

Thanks

> 
> Thanks,
> Pavel
> 
> > -----Original Message-----
> > From: Popov, Pavel E <pavel.e.popov@intel.com>
> > Sent: Tuesday, October 20, 2026 10:38 AM
> > To: Bjorn Helgaas <bhelgaas@google.com>; Logan Gunthorpe
> > <logang@deltatee.com>
> > Cc: Popov, Pavel E <pavel.e.popov@intel.com>; Leon Romanovsky
> > <leon@kernel.org>; Lukas Wunner <lukas@wunner.de>; Jim Chow
> > <jim.chow@broadcom.com>; Radu Rugina <radu.rugina@broadcom.com>;
> > Alexey Makhalov <alexey.makhalov@broadcom.com>; Wei Liu
> > <wei.liu@kernel.org>; Michael Kelley <mhklinux@outlook.com>; Nathan
> > Ciobanu <nathan.d.ciobanu@linux.intel.com>; bcm-kernel-feedback-
> > list@broadcom.com; virtualization@lists.linux.dev; linux-
> > hyperv@vger.kernel.org; linux-pci@vger.kernel.org; linux-
> > kernel@vger.kernel.org
> > Subject: [PATCH v4 0/2] PCI/P2PDMA: Allow P2PDMA on Intel Xeon server
> > CPUs
> > 
> > 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 on Intel hosts,
> > this series extends cpu_supports_p2pdma(), which so far covers AMD Zen and
> > newer, with an explicit list of Intel Xeon server generations.
> > 
> > Patch 1 moves the CONFIG_X86 #ifdef out of cpu_supports_p2pdma().
> > Patch 2 is the v3 patch rebased on it, with Logan's Reviewed-by carried over;
> > the Xeon list and the check are unchanged.
> > 
> > Changes in v4:
> > - Add 1/2, moving the CONFIG_X86 #ifdef out of cpu_supports_p2pdma()
> >   (Logan Gunthorpe, Leon Romanovsky)
> > - Keep the #ifdef around the asm/ includes, as these headers exist
> >   only on x86 (Bjorn Helgaas)
> > 
> > Changes in v3:
> > - Drop the hypervisor check and move the Xeon list into
> >   cpu_supports_p2pdma(), next to the AMD check, as suggested by Logan
> >   Gunthorpe and Leon Romanovsky [1]
> > - Fold the VMware and Hyper-V patches into one, as the check no longer
> >   depends on the hypervisor
> > 
> > Changes in v2:
> > - Replace the Skylake-and-newer threshold with an explicit list of Intel
> >   Xeon server generations, from Skylake-SP to Diamond Rapids (Logan
> >   Gunthorpe)
> > - Move the CONFIG_X86 #ifdef out of hypervisor_supports_p2pdma()
> >   (Logan Gunthorpe)
> > - Rebased on current mainline
> > 
> > [1] https://lore.kernel.org/r/20261016153147.GC219304@unreal
> > 
> > v3: https://lore.kernel.org/r/20261020151305.65218-1-
> > pavel.e.popov@intel.com
> > v2: https://lore.kernel.org/r/20261016223402.19991-1-
> > pavel.e.popov@intel.com
> > v1: https://lore.kernel.org/r/20261009154034.82321-1-
> > pavel.e.popov@intel.com
> > 
> > Pavel Popov (2):
> >   PCI/P2PDMA: Move CONFIG_X86 #ifdef out of cpu_supports_p2pdma()
> >   PCI/P2PDMA: Allow P2PDMA on Intel Xeon server CPUs
> > 
> >  drivers/pci/p2pdma.c | 33 +++++++++++++++++++++++++++++++--
> >  1 file changed, 31 insertions(+), 2 deletions(-)
> > 
> > 
> > base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
> > --
> > 2.53.0
>