[PATCH 1/1] PCI: Fix Extend ACS configurability

Tushar Dave
2024-12-13T20:30:19Z

Commit 47c8846a49ba ("PCI: Extend ACS configurability") introduced a
bug that fails to configure ACS ctrl for multiple PCI devices. It
affects both 'config_acs' and 'disable_acs_redir'.

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

[ 0.000000] Kernel command line: pci=config_acs=1111011@0020:02:00.0;101xxxx@0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p" earlycon
[ 12.349875] PCI: Can't parse ACS command line parameter
[ 19.629314] pci 0020:02:00.0: ACS mask = 0x007f
[ 19.629315] pci 0020:02:00.0: ACS flags = 0x007b
[ 19.629316] pci 0020:02:00.0: Configured ACS to 0x007b

After this fix:

[ 0.000000] Kernel command line: pci=config_acs=1111011@0020:02:00.0;101xxxx@0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p" earlycon
[ 19.583814] pci 0020:02:00.0: ACS mask = 0x007f
[ 19.588532] pci 0020:02:00.0: ACS flags = 0x007b
[ 19.593249] pci 0020:02:00.0: ACS control = 0x001d
[ 19.598143] pci 0020:02:00.0: Configured ACS to 0x007b
[ 24.088699] pci 0039:00:00.0: ACS mask = 0x0070
[ 24.093416] pci 0039:00:00.0: ACS flags = 0x0050
[ 24.098136] pci 0039:00:00.0: ACS control = 0x001d
[ 24.103031] pci 0039:00:00.0: Configured ACS to 0x005d

For example, using 'disable_acs_redire' fails to clear all three ACS P2P
redir bits:

[ 0.000000] 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" earlycon
[ 19.615860] pci 0020:02:00.0: ACS mask = 0x002c
[ 19.615862] pci 0020:02:00.0: ACS flags = 0xffd3
[ 19.615863] pci 0020:02:00.0: Configured ACS to 0xfffb
[ 22.332683] pci 0030:02:00.0: ACS mask = 0x002c
[ 22.332685] pci 0030:02:00.0: ACS flags = 0xffd3
[ 22.332686] pci 0030:02:00.0: Configured ACS to 0xffdf
[ 24.110278] pci 0039:00:00.0: ACS mask = 0x002c
[ 24.110281] pci 0039:00:00.0: ACS flags = 0xffd3
[ 24.110283] pci 0039:00:00.0: Configured ACS to 0xffd3

After this fix:

[ 0.000000] 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" earlycon
[ 19.597909] pci 0020:02:00.0: ACS mask = 0x002c
[ 19.597910] pci 0020:02:00.0: ACS flags = 0xffd3
[ 19.597911] pci 0020:02:00.0: ACS control = 0x007f
[ 19.597911] pci 0020:02:00.0: Configured ACS to 0x0053
[ 22.314124] pci 0030:02:00.0: ACS mask = 0x002c
[ 22.314126] pci 0030:02:00.0: ACS flags = 0xffd3
[ 22.314127] pci 0030:02:00.0: ACS control = 0x005f
[ 22.314128] pci 0030:02:00.0: Configured ACS to 0x0053
[ 24.091711] pci 0039:00:00.0: ACS mask = 0x002c
[ 24.091712] pci 0039:00:00.0: ACS flags = 0xffd3
[ 24.091714] pci 0039:00:00.0: ACS control = 0x001d
[ 24.091715] pci 0039:00:00.0: Configured ACS to 0x0011

Fixes: 47c8846a49ba ("PCI: Extend ACS configurability")
Signed-off-by: Tushar Dave <tdave@nvidia.com>
---
Documentation/admin-guide/kernel-parameters.txt | 11 +++++------
drivers/pci/pci.c | 16 +++++++++-------
2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index dc663c0ca670..fc1c37910d1c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4654,11 +4654,10 @@
Format:
<ACS flags>@<pci_dev>[; ...]
Specify one or more PCI devices (in the format
- specified above) optionally prepended with flags
- and separated by semicolons. The respective
- capabilities will be enabled, disabled or
- unchanged based on what is specified in
- flags.
+ specified above) prepended with flags and separated
+ by semicolons. The respective capabilities will be
+ enabled, disabled or unchanged based on what is
+ specified in flags.

ACS Flags is defined as follows:
bit-0 : ACS Source Validation
@@ -4673,7 +4672,7 @@
'1' – force enabled
'x' – unchanged
For example,
- pci=config_acs=10x
+ pci=config_acs=10x@pci:0:0
would configure all devices that support
ACS to enable P2P Request Redirect, disable
Translation Blocking, and leave Source
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 0b29ec6e8e5e..35ff21b014ac 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -951,12 +951,13 @@ static const char *config_acs_param;
struct pci_acs {
u16 cap;
u16 ctrl;
- u16 fw_ctrl;
};

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 +965,7 @@ 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 +973,8 @@ 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 +1031,10 @@ 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);

- /* 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;
+ caps->ctrl &= ~mask;
+ caps->ctrl |= (flags & mask);

pci_info(dev, "Configured ACS to %#06x\n", caps->ctrl);
}
@@ -1082,7 +1085,6 @@ static void pci_enable_acs(struct pci_dev *dev)

pci_read_config_word(dev, pos + PCI_ACS_CAP, &caps.cap);
pci_read_config_word(dev, pos + PCI_ACS_CTRL, &caps.ctrl);
- caps.fw_ctrl = caps.ctrl;

if (enable_acs)
pci_std_enable_acs(dev, &caps);
--
2.34.1