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Received: from guinness.priv.deltatee.com ([172.16.1.162]) by ale.deltatee.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.98.2) (envelope-from ) id 1xJCOE-00000000yyj-0mXr; Tue, 20 Oct 2026 10:08:38 -0600 Message-ID: Date: Tue, 20 Oct 2026 10:08:30 -0600 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Pavel Popov , Bjorn Helgaas Cc: Leon Romanovsky , Lukas Wunner , Jim Chow , Radu Rugina , Alexey Makhalov , Wei Liu , Michael Kelley , Nathan Ciobanu , 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 References: <20261020151305.65218-1-pavel.e.popov@intel.com> Content-Language: en-CA From: Logan Gunthorpe In-Reply-To: <20261020151305.65218-1-pavel.e.popov@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: pavel.e.popov@intel.com, bhelgaas@google.com, leon@kernel.org, lukas@wunner.de, jim.chow@broadcom.com, radu.rugina@broadcom.com, alexey.makhalov@broadcom.com, wei.liu@kernel.org, mhklinux@outlook.com, 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 X-SA-Exim-Mail-From: logang@deltatee.com X-Spam-Level: Subject: Re: [PATCH v3] PCI/P2PDMA: Allow P2PDMA on Intel Xeon server CPUs X-SA-Exim-Version: 4.2.1 (built Sun, 23 Feb 2025 07:57:16 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) On 2026-10-20 09:13, Pavel Popov wrote: > Peer-to-Peer DMA (P2PDMA) between two devices requires either a shared > upstream bridge or a host bridge matching pci_p2pdma_whitelist[]. In > VMware guests, passthrough devices appear directly on virtual root > buses without host bridge devices. In Hyper-V guests, each passthrough > device appears in a PCI domain of its own without a host bridge > device. Consequently, P2PDMA checks evaluate endpoint Device IDs > against the host bridge whitelist, causing P2PDMA requests to fail > regardless of host support. > > This affects discrete devices such as GPUs, NICs and NVMe drives. > > Add an explicit list of the Intel Xeon server generations from > Skylake-SP to Diamond Rapids to cpu_supports_p2pdma(). These are the > CPUs whose host bridges are in pci_p2pdma_whitelist[] without > restrictions. AMD Zen and newer are already covered by > cpu_supports_p2pdma(), so only Intel entries are needed. > > Tested with the Intel Level Zero P2P benchmark (ze_peer) on Arc Pro B60 > cards in a Linux guest on VMware ESXi 9.0 (Emerald Rapids host). > > Signed-off-by: Pavel Popov I can get behind this: Reviewed-by: Logan Gunthorpe Thanks, Logan