[{"id":3686691,"web_url":"http://patchwork.ozlabs.org/comment/3686691/","msgid":"<20260505203651.6D631C2BCB4@smtp.kernel.org>","list_archive_url":null,"date":"2026-05-05T20:36:50","subject":"Re: [PATCH 2/3] PCI/IOV: Restore initial VF ReBAR sizes on SR-IOV\n disable/failure","submitter":{"id":93311,"url":"http://patchwork.ozlabs.org/api/people/93311/","name":null,"email":"sashiko-bot@kernel.org"},"content":"Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:\n- [High] Early error returns in sriov_enable() bypass the newly introduced sriov_restore_vf_rebar_initial_sizes() cleanup.\n--\n\ncommit 4da183a318507a36de3ca157ee8755ad1eec90ca\nAuthor: Marcin Bernatowicz \n\nPCI/IOV: Restore initial VF ReBAR sizes on SR-IOV disable/failure\n\nThis commit introduces a mechanism to restore the initial VF BAR sizes when\nSR-IOV is disabled or when enabling it fails. This prevents the PCI core\nfrom persisting inflated VF BAR sizes, which can lead to MMIO space exhaustion.\n\nCloses: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/5937\n\n> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c\n> index 217e133a38c73..a05c1be388d2f 100644\n> --- a/drivers/pci/iov.c\n> +++ b/drivers/pci/iov.c\n\n[ ... ]\n\n> @@ -687,36 +721,42 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)\n> \t}\n> \tif (nres != iov->nres) {\n> \t\tpci_err(dev, \"not enough MMIO resources for SR-IOV\\n\");\n> -\t\treturn -ENOMEM;\n> +\t\trc = -ENOMEM;\n> +\t\tgoto err_restore;\n> \t}\n\nShould the earlier error returns in sriov_enable() also jump to err_restore?\n\nThere are early validation checks before this point that return directly:\n\ndrivers/pci/iov.c:sriov_enable() {\n ...\n\tpci_read_config_word(dev, iov->pos + PCI_SRIOV_INITIAL_VF, &initial);\n\tif (initial > iov->total_VFs ||\n\t (!(iov->cap & PCI_SRIOV_CAP_VFM) && (initial != iov->total_VFs)))\n\t\treturn -EIO;\n\n\tif (nr_virtfn < 0 || nr_virtfn > iov->total_VFs ||\n\t (!(iov->cap & PCI_SRIOV_CAP_VFM) && (nr_virtfn > initial)))\n\t\treturn -EINVAL;\n ...\n}\n\nIf an early exit occurs here, the hardware BAR remains inflated and\niov->num_VFs remains 0.\n\nBecause iov->num_VFs is 0, subsequent cleanup calls like pci_disable_sriov()\nduring driver teardown or system shutdown will bypass the restore logic due to\nthe early return in sriov_disable():\n\ndrivers/pci/iov.c:sriov_disable() {\n\tstruct pci_sriov *iov = dev->sriov;\n\n\tif (!iov->num_VFs)\n\t\treturn;\n ...\n}\n\nWill this leave the hardware BAR permanently inflated across kexec or warm\nreboots, potentially leading to the MMIO space exhaustion this patch aims to\nfix?","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=EpEp1D1H;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c09:e001:a7::12fc:5321; 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