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PCI/ACS: Fix 'pci=config_acs=' parameter

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[ Upstream commit 9cf8a952d57b422d3ff8a9a0163f8adf694f4b2b ]

Commit 47c8846a49 ("PCI: Extend ACS configurability") introduced bugs
that fail to configure ACS ctrl to the value specified by the kernel
parameter. Essentially there are two bugs:

1) When ACS is configured for multiple PCI devices using 'config_acs'
   kernel parameter, it results into error "PCI: Can't parse ACS command
   line parameter". This is due to a bug that doesn't preserve the ACS
   mask, but instead overwrites the mask with value 0.

   For example, using 'config_acs' to configure ACS ctrl for multiple BDFs
   fails:

      Kernel command line: pci=config_acs=1111011@0020:02:00.0;101xxxx@0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p"
      PCI: Can't parse ACS command line parameter
      pci 0020:02:00.0: ACS mask  = 0x007f
      pci 0020:02:00.0: ACS flags = 0x007b
      pci 0020:02:00.0: Configured ACS to 0x007b

   After this fix:

      Kernel command line: pci=config_acs=1111011@0020:02:00.0;101xxxx@0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p"
      pci 0020:02:00.0: ACS mask  = 0x007f
      pci 0020:02:00.0: ACS flags = 0x007b
      pci 0020:02:00.0: ACS control = 0x005f
      pci 0020:02:00.0: ACS fw_ctrl = 0x0053
      pci 0020:02:00.0: Configured ACS to 0x007b
      pci 0039:00:00.0: ACS mask  = 0x0070
      pci 0039:00:00.0: ACS flags = 0x0050
      pci 0039:00:00.0: ACS control = 0x001d
      pci 0039:00:00.0: ACS fw_ctrl = 0x0000
      pci 0039:00:00.0: Configured ACS to 0x0050

2) In the bit manipulation logic, we copy the bit from the firmware
   settings when mask bit 0.

   For example, 'disable_acs_redir' fails to clear all three ACS P2P redir
   bits due to the wrong bit fiddling:

      Kernel command line: pci=disable_acs_redir=0020:02:00.0;0030:02:00.0;0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p"
      pci 0020:02:00.0: ACS mask  = 0x002c
      pci 0020:02:00.0: ACS flags = 0xffd3
      pci 0020:02:00.0: Configured ACS to 0xfffb
      pci 0030:02:00.0: ACS mask  = 0x002c
      pci 0030:02:00.0: ACS flags = 0xffd3
      pci 0030:02:00.0: Configured ACS to 0xffdf
      pci 0039:00:00.0: ACS mask  = 0x002c
      pci 0039:00:00.0: ACS flags = 0xffd3
      pci 0039:00:00.0: Configured ACS to 0xffd3

   After this fix:

      Kernel command line: pci=disable_acs_redir=0020:02:00.0;0030:02:00.0;0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p"
      pci 0020:02:00.0: ACS mask  = 0x002c
      pci 0020:02:00.0: ACS flags = 0xffd3
      pci 0020:02:00.0: ACS control = 0x007f
      pci 0020:02:00.0: ACS fw_ctrl = 0x007b
      pci 0020:02:00.0: Configured ACS to 0x0053
      pci 0030:02:00.0: ACS mask  = 0x002c
      pci 0030:02:00.0: ACS flags = 0xffd3
      pci 0030:02:00.0: ACS control = 0x005f
      pci 0030:02:00.0: ACS fw_ctrl = 0x005f
      pci 0030:02:00.0: Configured ACS to 0x0053
      pci 0039:00:00.0: ACS mask  = 0x002c
      pci 0039:00:00.0: ACS flags = 0xffd3
      pci 0039:00:00.0: ACS control = 0x001d
      pci 0039:00:00.0: ACS fw_ctrl = 0x0000
      pci 0039:00:00.0: Configured ACS to 0x0000

Link: https://lore.kernel.org/r/20250207030338.456887-1-tdave@nvidia.com
Fixes: 47c8846a49 ("PCI: Extend ACS configurability")
Signed-off-by: Tushar Dave <tdave@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Tushar Dave
2025-02-06 19:03:38 -08:00
committed by Greg Kroah-Hartman
parent 91b0ab8751
commit 8ba27aa512
1 changed files with 13 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
drivers/pci/pci.c
View File

@@ -955,8 +955,10 @@ struct pci_acs {
};
static void __pci_config_acs(struct pci_dev *dev, struct pci_acs *caps,
const char *p, u16 mask, u16 flags)
const char *p, const u16 acs_mask, const u16 acs_flags)
{
u16 flags = acs_flags;
u16 mask = acs_mask;
char *delimit;
int ret = 0;
@@ -964,7 +966,7 @@ static void __pci_config_acs(struct pci_dev *dev, struct pci_acs *caps,
return;
while (*p) {
if (!mask) {
if (!acs_mask) {
/* Check for ACS flags */
delimit = strstr(p, "@");
if (delimit) {
@@ -972,6 +974,8 @@ static void __pci_config_acs(struct pci_dev *dev, struct pci_acs *caps,
u32 shift = 0;
end = delimit - p - 1;
mask = 0;
flags = 0;
while (end > -1) {
if (*(p + end) == '0') {
@@ -1028,10 +1032,14 @@ static void __pci_config_acs(struct pci_dev *dev, struct pci_acs *caps,
pci_dbg(dev, "ACS mask = %#06x\n", mask);
pci_dbg(dev, "ACS flags = %#06x\n", flags);
pci_dbg(dev, "ACS control = %#06x\n", caps->ctrl);
pci_dbg(dev, "ACS fw_ctrl = %#06x\n", caps->fw_ctrl);
/* If mask is 0 then we copy the bit from the firmware setting. */
caps->ctrl = (caps->ctrl & ~mask) | (caps->fw_ctrl & mask);
caps->ctrl |= flags;
/*
* For mask bits that are 0, copy them from the firmware setting
* and apply flags for all the mask bits that are 1.
*/
caps->ctrl = (caps->fw_ctrl & ~mask) | (flags & mask);
pci_info(dev, "Configured ACS to %#06x\n", caps->ctrl);
}