[PATCH 14/14 v3] PCI: Remove '*val = 0' from pcie_capability_read_*()
From: Bolarinwa Olayemi Saheed
There are several reasons why a PCI capability read may fail whether the
device is present or not. If this happens, pcie_capability_read_*() will
return -EINVAL/PCIBIOS_BAD_REGISTER_NUMBER or PCIBIOS_DEVICE_NOT_FOUND
and *val is set to 0.
This behaviour if further ensured by this code inside
pcie_capability_read_*()
ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
/*
* Reset *val to 0 if pci_read_config_dword() fails, it may
* have been written as 0x if hardware error happens
* during pci_read_config_dword().
*/
if (ret)
*val = 0;
return ret;
a) Since all pci_generic_config_read() does is read a register value,
it may return success after reading a ~0 which *may* have been fabricated
by the PCI host bridge due to a read timeout. Hence pci_read_config_*()
will return success with a fabricated ~0 in *val, indicating a problem.
In this case, the assumed behaviour of pcie_capability_read_*() will be
wrong. To avoid error slipping through, more checks are necessary.
b) pci_read_config_*() will return PCIBIOS_DEVICE_NOT_FOUND only if
dev->error_state = pci_channel_io_perm_failure (i.e.
pci_dev_is_disconnected()) or if pci_generic_config_read() can't find the
device. In both cases *val is initially set to ~0 but as shown in the code
above pcie_capability_read_*() resets it back to 0. Even with this effort,
drivers still have to perform validation checks more so if 0 is a valid
value.
Most drivers only consider the case (b) and in some cases, there is the
expectation that on timeout *val has a fabricated value of ~0, which *may*
not always be true as explained in (a).
In any case, checks need to be done to validate the value read and maybe
confirm which error has occurred. It is better left to the drivers to do.
Remove the reset of *val to 0 when pci_read_config_*() fails.
Suggested-by: Bjorn Helgaas
Signed-off-by: Bolarinwa Olayemi Saheed
---
This patch depends on all of the preceeding patches in this series,
otherwise it will introduce bugs as pointed out in the commit message
of each.
drivers/pci/access.c | 14 --
1 file changed, 14 deletions(-)
diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index 79c4a2ef269a..ec95edbb1ac8 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -413,13 +413,6 @@ int pcie_capability_read_word(struct pci_dev *dev, int
pos, u16 *val)
if (pcie_capability_reg_implemented(dev, pos)) {
ret = pci_read_config_word(dev, pci_pcie_cap(dev) + pos, val);
- /*
-* Reset *val to 0 if pci_read_config_word() fails, it may
-* have been written as 0x if hardware error happens
-* during pci_read_config_word().
-*/
- if (ret)
- *val = 0;
return ret;
}
@@ -448,13 +441,6 @@ int pcie_capability_read_dword(struct pci_dev *dev, int
pos, u32 *val)
if (pcie_capability_reg_implemented(dev, pos)) {
ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
- /*
-* Reset *val to 0 if pci_read_config_dword() fails, it may
-* have been written as 0x if hardware error happens
-* during pci_read_config_dword().
-*/
- if (ret)
- *val = 0;
return ret;
}
--
2.18.2
[PATCH 0/14 v3] PCI: Remove '*val = 0' from pcie_capability_read_*()
From: Bolarinwa Olayemi Saheed v3 CHANGES: - Split previous PATCH 6/13 into two : PATCH 6/14 and PATCH 7/14 - Fix commit message of PATCH 5/14 - Update Patch numbering and Commit messages - Add 'Acked by Greg KH' to PATCH 2/14 - Add PATCH version v2 CHANGES: - Fix missing comma, causing the email cc error - Fix typos and numbering errors in commit messages - Add commit message to 13/13 - Add two more patches: PATCH 3/13 and PATCH 4/13 MERGING: Patch 7/14 depends on Patch 6/14. However Patch 6/14 has no dependency. Please, merge PATCH 7/14 only after Patch 6/14. Patch 14/14 depend on all preceeding patchs. Except for Patch 6/14 and Patch 7/14, all other patches are independent of one another. Hence, please merge Patch 14/14 only after other patches in this series have been merged. PATCH 6/14: Make the function set status to "Power On" by default and only set to Set "Power Off" only if pcie_capability_read_word() is successful and (slot_ctrl & PCI_EXP_SLTCTL_PCC) == PCI_EXP_SLTCTL_PWR_OFF. PATCH 1/14 to 13/14: Check the return value of pcie_capability_read_*() to ensure success or confirm failure. While maintaining these functions, this ensures that the changes in PATCH 14/14 does not introduce any bug. PATCH 14/14: There are several reasons why a PCI capability read may fail whether the device is present or not. If this happens, pcie_capability_read_*() will return -EINVAL/PCIBIOS_BAD_REGISTER_NUMBER or PCIBIOS_DEVICE_NOT_FOUND and *val is set to 0. This behaviour if further ensured by this code inside pcie_capability_read_*() ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val); /* * Reset *val to 0 if pci_read_config_dword() fails, it may * have been written as 0x if hardware error happens * during pci_read_config_dword(). */ if (ret) *val = 0; return ret; a) Since all pci_generic_config_read() does is read a register value, it may return success after reading a ~0 which *may* have been fabricated by the PCI host bridge due to a read timeout. Hence pci_read_config_*() will return success with a fabricated ~0 in *val, indicating a problem. In this case, the assumed behaviour of pcie_capability_read_*() will be wrong. To avoid error slipping through, more checks are necessary. b) pci_read_config_*() will return PCIBIOS_DEVICE_NOT_FOUND only if dev->error_state = pci_channel_io_perm_failure (i.e. pci_dev_is_disconnected()) or if pci_generic_config_read() can't find the device. In both cases *val is initially set to ~0 but as shown in the code above pcie_capability_read_*() resets it back to 0. Even with this effort, drivers still have to perform validation checks more so if 0 is a valid value. Most drivers only consider the case (b) and in some cases, there is the expectation that on timeout *val has a fabricated value of ~0, which *may* not always be true as explained in (a). In any case, checks need to be done to validate the value read and maybe confirm which error has occurred. It is better left to the drivers to do. Check the return value of pcie_capability_read_dword() to ensure success and avoid bug as a result of Patch 14/14. Remove the reset of *val to 0 when pci_read_config_*() fails. Bolarinwa Olayemi Saheed (14): IB/hfi1: Check the return value of pcie_capability_read_*() misc: rtsx: Check the return value of pcie_capability_read_*() ath9k: Check the return value of pcie_capability_read_*() iwlegacy: Check the return value of pcie_capability_read_*() PCI: pciehp: Check the return value of pcie_capability_read_*() PCI: pciehp: Make "Power On" the default PCI: pciehp: Check the return value of pcie_capability_read_*() PCI/ACPI: Check the return value of pcie_capability_read_*() PCI: pciehp: Check the return value of pcie_capability_read_*() PCI: Check the return value of pcie_capability_read_*() PCI/PM: Check return value of pcie_capability_read_*() PCI/AER: Check the return value of pcie_capability_read_*() PCI/ASPM: Check the return value of pcie_capability_read_*() PCI: Remove '*val = 0' from pcie_capability_read_*() drivers/net/wireless/ath/ath9k/pci.c | 5 +++-- drivers/net/wireless/intel/iwlegacy/common.c | 4 ++-- drivers/infiniband/hw/hfi1/aspm.c | 7 --- drivers/misc/cardreader/rts5227.c | 5 +++-- drivers/misc/cardreader/rts5249.c | 5 +++-- drivers/misc/cardreader/rts5260.c | 5 +++-- drivers/misc/cardreader/rts5261.c | 5 +++-- drivers/pci/pcie/aer.c | 5 +++-- drivers/pci/pcie/aspm.c | 33 + drivers/pci/hotplug/pciehp_hpc.c | 47 drivers/pci/pci-acpi.c | 10 --- drivers/pci/probe.c | 29 drivers/pci/access.c | 14 -- 13 files changed, 87 insertions(+), 87 deletions(-) -- 2.18.2
[PATCH 13/13] PCI: Remove '*val = 0' from pcie_capability_read_*()
From: Bolarinwa Olayemi Saheed
There are several reasons why a PCI capability read may fail whether the
device is present or not. If this happens, pcie_capability_read_*() will
return -EINVAL/PCIBIOS_BAD_REGISTER_NUMBER or PCIBIOS_DEVICE_NOT_FOUND
and *val is set to 0.
This behaviour if further ensured by this code inside
pcie_capability_read_*()
ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
/*
* Reset *val to 0 if pci_read_config_dword() fails, it may
* have been written as 0x if hardware error happens
* during pci_read_config_dword().
*/
if (ret)
*val = 0;
return ret;
a) Since all pci_generic_config_read() does is read a register value,
it may return success after reading a ~0 which *may* have been fabricated
by the PCI host bridge due to a read timeout. Hence pci_read_config_*()
will return success with a fabricated ~0 in *val, indicating a problem.
In this case, the assumed behaviour of pcie_capability_read_*() will be
wrong. To avoid error slipping through, more checks are necessary.
b) pci_read_config_*() will return PCIBIOS_DEVICE_NOT_FOUND only if
dev->error_state = pci_channel_io_perm_failure (i.e.
pci_dev_is_disconnected()) or if pci_generic_config_read() can't find the
device. In both cases *val is initially set to ~0 but as shown in the code
above pcie_capability_read_*() resets it back to 0. Even with this effort,
drivers still have to perform validation checks more so if 0 is a valid
value.
Most drivers only consider the case (b) and in some cases, there is the
expectation that on timeout *val has a fabricated value of ~0, which *may*
not always be true as explained in (a).
In any case, checks need to be done to validate the value read and maybe
confirm which error has occurred. It is better left to the drivers to do.
Remove the reset of *val to 0 when pci_read_config_*() fails.
Suggested-by: Bjorn Helgaas
Signed-off-by: Bolarinwa Olayemi Saheed
---
This patch depends on all of the preceeding patches in this series,
otherwise it will introduce bugs as pointed out in the commit message
of each.
drivers/pci/access.c | 14 --
1 file changed, 14 deletions(-)
diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index 79c4a2ef269a..ec95edbb1ac8 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -413,13 +413,6 @@ int pcie_capability_read_word(struct pci_dev *dev, int
pos, u16 *val)
if (pcie_capability_reg_implemented(dev, pos)) {
ret = pci_read_config_word(dev, pci_pcie_cap(dev) + pos, val);
- /*
-* Reset *val to 0 if pci_read_config_word() fails, it may
-* have been written as 0x if hardware error happens
-* during pci_read_config_word().
-*/
- if (ret)
- *val = 0;
return ret;
}
@@ -448,13 +441,6 @@ int pcie_capability_read_dword(struct pci_dev *dev, int
pos, u32 *val)
if (pcie_capability_reg_implemented(dev, pos)) {
ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
- /*
-* Reset *val to 0 if pci_read_config_dword() fails, it may
-* have been written as 0x if hardware error happens
-* during pci_read_config_dword().
-*/
- if (ret)
- *val = 0;
return ret;
}
--
2.18.2
[PATCH 0/13] PCI: Remove '*val = 0' from pcie_capability_read_*()
From: Bolarinwa Olayemi Saheed MERGING: Only Patch 13/13 depend on all preceeding patchs. All other patches are independent of one another. Hence, please merge PATCH 13/13 only after other patches in this series have been merged. PATCH 6/13: Make the function set status to "Power On" by default and only set to Set "Power Off" only if pcie_capability_read_word() is successful and (slot_ctrl & PCI_EXP_SLTCTL_PCC) == PCI_EXP_SLTCTL_PWR_OFF. PATCH 1/13 to 12/13: Check the return value of pcie_capability_read_*() to ensure success or confirm failure. While maintaining these functions, this ensures that the changes in PATCH 13/13 does not introduce any bug. PATCH 13/13: There are several reasons why a PCI capability read may fail whether the device is present or not. If this happens, pcie_capability_read_*() will return -EINVAL/PCIBIOS_BAD_REGISTER_NUMBER or PCIBIOS_DEVICE_NOT_FOUND and *val is set to 0. This behaviour if further ensured by this code inside pcie_capability_read_*() ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val); /* * Reset *val to 0 if pci_read_config_dword() fails, it may * have been written as 0x if hardware error happens * during pci_read_config_dword(). */ if (ret) *val = 0; return ret; a) Since all pci_generic_config_read() does is read a register value, it may return success after reading a ~0 which *may* have been fabricated by the PCI host bridge due to a read timeout. Hence pci_read_config_*() will return success with a fabricated ~0 in *val, indicating a problem. In this case, the assumed behaviour of pcie_capability_read_*() will be wrong. To avoid error slipping through, more checks are necessary. b) pci_read_config_*() will return PCIBIOS_DEVICE_NOT_FOUND only if dev->error_state = pci_channel_io_perm_failure (i.e. pci_dev_is_disconnected()) or if pci_generic_config_read() can't find the device. In both cases *val is initially set to ~0 but as shown in the code above pcie_capability_read_*() resets it back to 0. Even with this effort, drivers still have to perform validation checks more so if 0 is a valid value. Most drivers only consider the case (b) and in some cases, there is the expectation that on timeout *val has a fabricated value of ~0, which *may* not always be true as explained in (a). In any case, checks need to be done to validate the value read and maybe confirm which error has occurred. It is better left to the drivers to do. Check the return value of pcie_capability_read_dword() to ensure success and avoid bug as a result of Patch 13/13. Remove the reset of *val to 0 when pci_read_config_*() fails. Bolarinwa Olayemi Saheed (13): IB/hfi1: Check the return value of pcie_capability_read_*() misc: rtsx: Check the return value of pcie_capability_read_*() ath9k: Check the return value of pcie_capability_read_*() iwlegacy: Check the return value of pcie_capability_read_*() PCI: pciehp: Check the return value of pcie_capability_read_*() PCI: pciehp: Make "Power On" the default PCI/ACPI: Check the return value of pcie_capability_read_*() PCI: pciehp: Check the return value of pcie_capability_read_*() PCI: Check the return value of pcie_capability_read_*() PCI/PM: Check return value of pcie_capability_read_*() PCI/AER: Check the return value of pcie_capability_read_*() PCI/ASPM: Check the return value of pcie_capability_read_*() PCI: Remove '*val = 0' from pcie_capability_read_*() drivers/net/wireless/ath/ath9k/pci.c | 5 +++-- drivers/net/wireless/intel/iwlegacy/common.c | 4 ++-- drivers/infiniband/hw/hfi1/aspm.c | 7 --- drivers/misc/cardreader/rts5227.c | 5 +++-- drivers/misc/cardreader/rts5249.c | 5 +++-- drivers/misc/cardreader/rts5260.c | 5 +++-- drivers/misc/cardreader/rts5261.c | 5 +++-- drivers/pci/pcie/aer.c | 5 +++-- drivers/pci/pcie/aspm.c | 33 + drivers/pci/hotplug/pciehp_hpc.c | 47 drivers/pci/pci-acpi.c | 10 --- drivers/pci/probe.c | 29 drivers/pci/access.c | 14 -- 13 files changed, 87 insertions(+), 87 deletions(-) -- 2.18.2
[PATCH 11/11 RFC] PCI: Remove "*val = 0" from pcie_capability_read_*()
From: Bolarinwa Olayemi Saheed
**TODO**
Suggested-by: Bjorn Helgaas
Signed-off-by: Bolarinwa Olayemi Saheed
---
This patch depends on all of the preceeding patches in this series,
otherwise it will introduce bugs as pointed out in the commit message
of each.
drivers/pci/access.c | 14 --
1 file changed, 14 deletions(-)
diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index 79c4a2ef269a..ec95edbb1ac8 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -413,13 +413,6 @@ int pcie_capability_read_word(struct pci_dev *dev, int
pos, u16 *val)
if (pcie_capability_reg_implemented(dev, pos)) {
ret = pci_read_config_word(dev, pci_pcie_cap(dev) + pos, val);
- /*
-* Reset *val to 0 if pci_read_config_word() fails, it may
-* have been written as 0x if hardware error happens
-* during pci_read_config_word().
-*/
- if (ret)
- *val = 0;
return ret;
}
@@ -448,13 +441,6 @@ int pcie_capability_read_dword(struct pci_dev *dev, int
pos, u32 *val)
if (pcie_capability_reg_implemented(dev, pos)) {
ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
- /*
-* Reset *val to 0 if pci_read_config_dword() fails, it may
-* have been written as 0x if hardware error happens
-* during pci_read_config_dword().
-*/
- if (ret)
- *val = 0;
return ret;
}
--
2.18.2
[PATCH 0/11 RFC] PCI: Remove "*val = 0" from pcie_capability_read_*()
From: Bolarinwa Olayemi Saheed *** BLURB HERE *** Bolarinwa Olayemi Saheed (9): IB/hfi1: Confirm that pcie_capability_read_dword() is successful misc: rtsx: Confirm that pcie_capability_read_word() is successful PCI/AER: Use error return value from pcie_capability_read_*() PCI/ASPM: Use error return value from pcie_capability_read_*() PCI: pciehp: Fix wrong failure check on pcie_capability_read_*() PCI: pciehp: Prevent wrong failure check on pcie_capability_read_*() PCI: pciehp: Make "Power On" the default in pciehp_get_power_status() PCI/ACPI: Prevent wrong failure check on pcie_capability_read_*() PCI: Prevent wrong failure check on pcie_capability_read_*() PCI: Remove "*val = 0" fom pcie_capability_read_*() drivers/infiniband/hw/hfi1/aspm.c | 7 --- drivers/misc/cardreader/rts5227.c | 5 +++-- drivers/misc/cardreader/rts5249.c | 5 +++-- drivers/misc/cardreader/rts5260.c | 5 +++-- drivers/misc/cardreader/rts5261.c | 5 +++-- drivers/pci/pcie/aer.c | 5 +++-- drivers/pci/pcie/aspm.c | 33 + drivers/pci/hotplug/pciehp_hpc.c | 47 drivers/pci/pci-acpi.c | 10 --- drivers/pci/probe.c | 29 drivers/pci/access.c | 14 -- 11 files changed, 82 insertions(+), 83 deletions(-) -- 2.18.2
