From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ale.deltatee.com (ale.deltatee.com [204.191.154.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 951763AEB49; Fri, 9 Oct 2026 16:39:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=204.191.154.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791563995; cv=none; b=pTotu+qh62U1kCUPfYhRIaO3hk/OiR7TXzZ7cTU62ZgIsdXPaAXqmMMLUUdW0Vf/oKWIyBS3yCcWOWx43I/JBsDFmCkuwArHwSudbbbqwWsX1aNJhLAv8jb97esTb7jnIvgkUDf/s+pCq/ga9TX5JtlbyapgCaBOsNBUw1KJAxg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791563995; c=relaxed/simple; bh=kk3kOTBPrArfp9d/qnBlVWwOPwFl/PxyCQqJWfcpwfw=; h=Message-ID:Date:MIME-Version:To:Cc:References:From:In-Reply-To: Content-Type:Subject; b=kYg+/3axPGlqYZtWLdUiHQtKJnNwlOTVVdPFVgzvJQrGjRCF6jqQyn8VHkortno41oNrqRHQCfwA/kZ/LIJvFqRcUp5eD+48psGOZgHUjqz0Coppy8zbJ1FhYZRFah4bxJSTFtJy3nFsWyvCpBx/mwLKlp19mSlaChY4Jp9ikVg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=deltatee.com; spf=pass smtp.mailfrom=deltatee.com; dkim=pass (2048-bit key) header.d=deltatee.com header.i=@deltatee.com header.b=mzV1eZT9; arc=none smtp.client-ip=204.191.154.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=deltatee.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=deltatee.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=deltatee.com header.i=@deltatee.com header.b="mzV1eZT9" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=deltatee.com; s=20200525; h=Subject:In-Reply-To:From:References:Cc:To: MIME-Version:Date:Message-ID:content-disposition; bh=TwwZvgIurBDct/fGCIzm1g3CVHGZhqUQFnU2wB165kw=; b=mzV1eZT92EWRc6SpJU/8u3daR2 EwVSbpikzGNpmvyY7INv8lib8QO4PhIGFbp1usv26p/Fbp1A8TlUTh3JldQkRJogfCWWbudZRfyI3 K87we1OhdY71eyKlJJhqlLthyxCBazOXAPkhxZHan0fAcFYpV3KHl/+TshM27zB1jm/avDx4ucCDF MGxcmdQc68qp+icmxbFPqJVgiP9vMTuvH3wBgBlb7GEqUQz5rQHul74Bqm8ulxlK4U0PtlChFA1M7 DRnwZSXMkKUOVo9l8DlqJke6HYyaHi/H6y5EehKsfxGna7jeINXhWzqhXtlGrSlhCOwFJ05aSk4r7 rUsDPVcA==; Received: from [104.157.31.28] (helo=[192.168.1.251]) by ale.deltatee.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.98.2) (envelope-from ) id 1xFDdL-00000002Me3-05mR; Fri, 09 Oct 2026 10:39:47 -0600 Message-ID: <91b08b3e-49dd-434e-a439-b3453c5ec3f3@deltatee.com> Date: Fri, 9 Oct 2026 10:38:08 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Pavel Popov , Bjorn Helgaas Cc: Jim Chow , Radu Rugina , Alexey Makhalov , bcm-kernel-feedback-list@broadcom.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org References: <20261009154034.82321-1-pavel.e.popov@intel.com> <20261009154034.82321-2-pavel.e.popov@intel.com> Content-Language: en-CA From: Logan Gunthorpe In-Reply-To: <20261009154034.82321-2-pavel.e.popov@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 104.157.31.28 X-SA-Exim-Rcpt-To: pavel.e.popov@intel.com, bhelgaas@google.com, jim.chow@broadcom.com, radu.rugina@broadcom.com, alexey.makhalov@broadcom.com, bcm-kernel-feedback-list@broadcom.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: logang@deltatee.com X-Spam-Level: Subject: Re: [PATCH 1/2] PCI/P2PDMA: Allow P2PDMA in VMware guests on Intel hosts 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 2026-10-09 9:40 a.m., 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. 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. > > The P2PDMA host bridge check does not work in a VMware guest. Bypass it on > Intel hosts under VMware, starting with Skylake-SP, the first Xeon > Scalable generation. Xeon Scalable introduced UPI and is whitelisted for > P2PDMA without restrictions. AMD Zen and newer are already covered by > cpu_supports_p2pdma(), so the bypass is implemented for Intel hosts only. > > 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). > > Reviewed-by: Jim Chow > Signed-off-by: Pavel Popov > --- > drivers/pci/p2pdma.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index 9334eb314663..d96f44d0738a 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -21,6 +21,12 @@ > #include > #include > > +#ifdef CONFIG_X86 > +#include > +#include > +#include > +#endif > + > struct pci_p2pdma { > struct gen_pool *pool; > bool p2pmem_published; > @@ -532,6 +538,19 @@ static bool cpu_supports_p2pdma(void) > return false; > } > > +static bool hypervisor_supports_p2pdma(void) > +{ > +#ifdef CONFIG_X86 > + /* Hypervisor hides host topology, allow p2pdma on Skylake and newer */ > + if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL && > + boot_cpu_data.x86_vfm >= INTEL_SKYLAKE_X && > + hypervisor_is_type(X86_HYPER_VMWARE)) > + return true; > +#endif > + > + return false; > +} The changes seem fine, but one minor nit from me. Can we avoid putting the #ifdefs inside the function? Something like: #ifdef CONFIG_X86 static bool hypervisor_supports_p2pdma(void) { ... } #else /* !CONFIG_X86 */ static bool hypervisor_supports_p2pdma(void) { return false; } #endif /* CONFIG_X86 */ Other than that, the core concept seems fine to me: Reviewed-by: Logan Gunthorpe Thanks! Logan