linux-kernel - [PATCH v2 1/2] PCI: Fix issue with "pci=disable_acs

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Message-Id: <20190410210532.4538-2-logang@deltatee.com>
Date:   Wed, 10 Apr 2019 15:05:31 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v2 1/2] PCI: Fix issue with "pci=disable_acs_redir" parameter being ignored

In most cases, kmalloc will not be available early in boot when
pci_setup() is called. Thus, the kstrdup call that was added to fix the
__initdata bug with the disable_acs_redir parameter usually returns
NULL. Thus the parameter is discarded and it does not take into effect.

To fix this, we store the string that's in initdata until a initcall
function can allocate the memory appropriately. This way we
don't need any additional static memory.

Fixes: d2fd6e81912a ("PCI: Fix __initdata issue with "pci=disable_acs_redir" parameter")
Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
---
 drivers/pci/pci.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7c1b362f599a..766f5779db92 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6262,8 +6262,7 @@ static int __init pci_setup(char *str)
 			} else if (!strncmp(str, "pcie_scan_all", 13)) {
 				pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
 			} else if (!strncmp(str, "disable_acs_redir=", 18)) {
-				disable_acs_redir_param =
-					kstrdup(str + 18, GFP_KERNEL);
+				disable_acs_redir_param = str + 18;
 			} else {
 				printk(KERN_ERR "PCI: Unknown option `%s'\n",
 						str);
@@ -6274,3 +6273,19 @@ static int __init pci_setup(char *str)
 	return 0;
 }
 early_param("pci", pci_setup);
+
+/*
+ * 'disable_acs_redir_param' is initialized in pci_setup(), above, to point
+ * to data in the __initdata section which will be freed after the init
+ * sequence is complete. We can't allocate memory in pci_setup() because some
+ * architectures do not have any memory allocation service available during
+ * an early_param() call. So we allocate memory and copy the variable here
+ * before the init section is freed.
+ */
+static int __init pci_realloc_setup_params(void)
+{
+	disable_acs_redir_param = kstrdup(disable_acs_redir_param, GFP_KERNEL);
+
+	return 0;
+}
+pure_initcall(pci_realloc_setup_params);
-- 
2.20.1