linux-kernel - Why does cdns_pcie_ep_set_bar use sz > SZ_2G for is

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <PH7PR19MB55626CD5D22EABDEC879EF41A0599@PH7PR19MB5562.namprd19.prod.outlook.com>
Date:   Wed, 19 Jan 2022 09:27:44 +0000
From:   Li Chen <lchen@...arella.com>
To:     Tom Joseph <tjoseph@...ence.com>
CC:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Why does cdns_pcie_ep_set_bar use sz > SZ_2G for is_64bits in
 pcie-cadence-ep.c?

Hi, Tom

>From these function:
static int cdns_pcie_ep_set_bar(struct pci_epc *epc, u8 fn, u8 vfn,
				struct pci_epf_bar *epf_bar)
{
	......
	if ((flags & PCI_BASE_ADDRESS_SPACE) == PCI_BASE_ADDRESS_SPACE_IO) {
		ctrl = CDNS_PCIE_LM_BAR_CFG_CTRL_IO_32BITS;
	} else {
		bool is_prefetch = !!(flags & PCI_BASE_ADDRESS_MEM_PREFETCH);
		bool is_64bits = sz > SZ_2G;
		if (is_64bits && (bar & 1))
			return -EINVAL;
		if (is_64bits && !(flags & PCI_BASE_ADDRESS_MEM_TYPE_64))
			epf_bar->flags |= PCI_BASE_ADDRESS_MEM_TYPE_64;

		if (is_64bits && is_prefetch)
			ctrl = CDNS_PCIE_LM_BAR_CFG_CTRL_PREFETCH_MEM_64BITS;
		else if (is_prefetch)
			ctrl = CDNS_PCIE_LM_BAR_CFG_CTRL_PREFETCH_MEM_32BITS;
		else if (is_64bits)
			ctrl = CDNS_PCIE_LM_BAR_CFG_CTRL_MEM_64BITS;
		else
			ctrl = CDNS_PCIE_LM_BAR_CFG_CTRL_MEM_32BITS;
	}

	......
}

I don't understand why should sz > SZ_2G be taken into account for 64_bits. From my personal practice, there is no problem to use CDNS_PCIE_LM_BAR_CFG_CTRL_MEM_64BITS or CDNS_PCIE_LM_BAR_CFG_CTRL_PREFETCH_MEM_64BITS when sz < SZ_2G.

Regards,
Li

**********************************************************************
This email and attachments contain Ambarella Proprietary and/or Confidential Information and is intended solely for the use of the individual(s) to whom it is addressed. Any unauthorized review, use, disclosure, distribute, copy, or print is prohibited. If you are not an intended recipient, please contact the sender by reply email and destroy all copies of the original message. Thank you.