| Message ID | 20250208050329.1092214-2-helgaas@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCI: Avoid capability searches in save/restore state | expand |
On Fri, 7 Feb 2025, Bjorn Helgaas wrote: > From: Bjorn Helgaas <bhelgaas@google.com> > > Many of the save/restore functions in the pci_save_state() and > pci_restore_state() paths depend on both a PCI capability of the device and > a pci_cap_saved_state structure to hold the configuration data, and they > skip the operation if either is missing. > > Look for the pci_cap_saved_state first so if we don't have one, we can skip > searching for the device capability, which requires several slow config > space accesses. > > Remove some error messages if the pci_cap_saved_state is not found so we > don't complain about having no saved state for a capability the device > doesn't have. We have already warned in pci_allocate_cap_save_buffers() if > the capability is present but we were unable to allocate a buffer. > > Other than the message change, no functional change intended. > > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> > --- > drivers/pci/pci.c | 27 ++++++++++++++------------- > drivers/pci/pcie/aspm.c | 15 ++++++++------- > drivers/pci/vc.c | 22 +++++++++++----------- > 3 files changed, 33 insertions(+), 31 deletions(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 869d204a70a3..503376bf7e75 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -1686,10 +1686,8 @@ static int pci_save_pcie_state(struct pci_dev *dev) > return 0; > > save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP); > - if (!save_state) { > - pci_err(dev, "buffer not found in %s\n", __func__); > + if (!save_state) > return -ENOMEM; > - } > > cap = (u16 *)&save_state->cap.data[0]; > pcie_capability_read_word(dev, PCI_EXP_DEVCTL, &cap[i++]); > @@ -1742,19 +1740,17 @@ static void pci_restore_pcie_state(struct pci_dev *dev) > > static int pci_save_pcix_state(struct pci_dev *dev) > { > - int pos; > struct pci_cap_saved_state *save_state; > + u8 pos; > + > + save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX); > + if (!save_state) > + return -ENOMEM; > > pos = pci_find_capability(dev, PCI_CAP_ID_PCIX); > if (!pos) > return 0; > > - save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX); > - if (!save_state) { > - pci_err(dev, "buffer not found in %s\n", __func__); > - return -ENOMEM; > - } > - > pci_read_config_word(dev, pos + PCI_X_CMD, > (u16 *)save_state->cap.data); > > @@ -1763,14 +1759,19 @@ static int pci_save_pcix_state(struct pci_dev *dev) > > static void pci_restore_pcix_state(struct pci_dev *dev) > { > - int i = 0, pos; > struct pci_cap_saved_state *save_state; > + u8 pos; > + int i = 0; > u16 *cap; > > save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX); > - pos = pci_find_capability(dev, PCI_CAP_ID_PCIX); > - if (!save_state || !pos) > + if (!save_state) > return; > + > + pos = pci_find_capability(dev, PCI_CAP_ID_PCIX); > + if (!pos) > + return; > + > cap = (u16 *)&save_state->cap.data[0]; > > pci_write_config_word(dev, pos + PCI_X_CMD, cap[i++]); > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > index e0bc90597dca..007e4a082e6f 100644 > --- a/drivers/pci/pcie/aspm.c > +++ b/drivers/pci/pcie/aspm.c > @@ -35,16 +35,14 @@ void pci_save_ltr_state(struct pci_dev *dev) > if (!pci_is_pcie(dev)) > return; > > + save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR); > + if (!save_state) > + return; > + > ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR); > if (!ltr) > return; > > - save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR); > - if (!save_state) { > - pci_err(dev, "no suspend buffer for LTR; ASPM issues possible after resume\n"); > - return; > - } > - > /* Some broken devices only support dword access to LTR */ > cap = &save_state->cap.data[0]; > pci_read_config_dword(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, cap); > @@ -57,8 +55,11 @@ void pci_restore_ltr_state(struct pci_dev *dev) > u32 *cap; > > save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR); > + if (!save_state) > + return; > + > ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR); > - if (!save_state || !ltr) > + if (!ltr) > return; > > /* Some broken devices only support dword access to LTR */ > diff --git a/drivers/pci/vc.c b/drivers/pci/vc.c > index a4ff7f5f66dd..c39f3be518d4 100644 > --- a/drivers/pci/vc.c > +++ b/drivers/pci/vc.c > @@ -355,20 +355,17 @@ int pci_save_vc_state(struct pci_dev *dev) > int i; > > for (i = 0; i < ARRAY_SIZE(vc_caps); i++) { > - int pos, ret; > struct pci_cap_saved_state *save_state; > + int pos, ret; > + > + save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > + if (!save_state) > + return -ENOMEM; > > pos = pci_find_ext_capability(dev, vc_caps[i].id); > if (!pos) > continue; > > - save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > - if (!save_state) { > - pci_err(dev, "%s buffer not found in %s\n", > - vc_caps[i].name, __func__); > - return -ENOMEM; > - } I think this order change will cause a functional change because pci_allocate_vc_save_buffers() only allocated for those capabilities that are exist for dev. Thus, the loop will prematurely exit. > - > ret = pci_vc_do_save_buffer(dev, pos, save_state, true); > if (ret) { > pci_err(dev, "%s save unsuccessful %s\n", > @@ -392,12 +389,15 @@ void pci_restore_vc_state(struct pci_dev *dev) > int i; > > for (i = 0; i < ARRAY_SIZE(vc_caps); i++) { > - int pos; > struct pci_cap_saved_state *save_state; > + int pos; > + > + save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > + if (!save_state) > + continue; > > pos = pci_find_ext_capability(dev, vc_caps[i].id); > - save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > - if (!save_state || !pos) > + if (!pos) > continue; > > pci_vc_do_save_buffer(dev, pos, save_state, false); >
On Thu, Feb 13, 2025 at 03:52:05PM +0200, Ilpo Järvinen wrote: > On Fri, 7 Feb 2025, Bjorn Helgaas wrote: > > Many of the save/restore functions in the pci_save_state() and > > pci_restore_state() paths depend on both a PCI capability of the device and > > a pci_cap_saved_state structure to hold the configuration data, and they > > skip the operation if either is missing. > > > > Look for the pci_cap_saved_state first so if we don't have one, we can skip > > searching for the device capability, which requires several slow config > > space accesses. > > +++ b/drivers/pci/vc.c > > @@ -355,20 +355,17 @@ int pci_save_vc_state(struct pci_dev *dev) > > int i; > > > > for (i = 0; i < ARRAY_SIZE(vc_caps); i++) { > > - int pos, ret; > > struct pci_cap_saved_state *save_state; > > + int pos, ret; > > + > > + save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > > + if (!save_state) > > + return -ENOMEM; > > > > pos = pci_find_ext_capability(dev, vc_caps[i].id); > > if (!pos) > > continue; > > > > - save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > > - if (!save_state) { > > - pci_err(dev, "%s buffer not found in %s\n", > > - vc_caps[i].name, __func__); > > - return -ENOMEM; > > - } > > I think this order change will cause a functional change because > pci_allocate_vc_save_buffers() only allocated for those capabilities that > are exist for dev. Thus, the loop will prematurely exit. Oof, thank you for catching this! I'll drop this for now. It would be nice to make pci_save_vc_state() parallel with pci_restore_vc_state() (and with most other pci_save_*_state() functions) and have it return void. But pci_save_state() returns the pci_save_vc_state() return value, and there are ~20 pci_save_state() callers that pay attention to that return value. I'm not convinced there's real value in pci_save_state() error returns, given that so few callers check it, but it definitely requires more analysis before removing it. > > ret = pci_vc_do_save_buffer(dev, pos, save_state, true); > > if (ret) { > > pci_err(dev, "%s save unsuccessful %s\n", > > @@ -392,12 +389,15 @@ void pci_restore_vc_state(struct pci_dev *dev) > > int i; > > > > for (i = 0; i < ARRAY_SIZE(vc_caps); i++) { > > - int pos; > > struct pci_cap_saved_state *save_state; > > + int pos; > > + > > + save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > > + if (!save_state) > > + continue; > > > > pos = pci_find_ext_capability(dev, vc_caps[i].id); > > - save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > > - if (!save_state || !pos) > > + if (!pos) > > continue; > > > > pci_vc_do_save_buffer(dev, pos, save_state, false); > > > > -- > i. >
On Thu, 13 Feb 2025, Bjorn Helgaas wrote: > On Thu, Feb 13, 2025 at 03:52:05PM +0200, Ilpo Järvinen wrote: > > On Fri, 7 Feb 2025, Bjorn Helgaas wrote: > > > Many of the save/restore functions in the pci_save_state() and > > > pci_restore_state() paths depend on both a PCI capability of the device and > > > a pci_cap_saved_state structure to hold the configuration data, and they > > > skip the operation if either is missing. > > > > > > Look for the pci_cap_saved_state first so if we don't have one, we can skip > > > searching for the device capability, which requires several slow config > > > space accesses. > > > > +++ b/drivers/pci/vc.c > > > @@ -355,20 +355,17 @@ int pci_save_vc_state(struct pci_dev *dev) > > > int i; > > > > > > for (i = 0; i < ARRAY_SIZE(vc_caps); i++) { > > > - int pos, ret; > > > struct pci_cap_saved_state *save_state; > > > + int pos, ret; > > > + > > > + save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > > > + if (!save_state) > > > + return -ENOMEM; > > > > > > pos = pci_find_ext_capability(dev, vc_caps[i].id); > > > if (!pos) > > > continue; > > > > > > - save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); > > > - if (!save_state) { > > > - pci_err(dev, "%s buffer not found in %s\n", > > > - vc_caps[i].name, __func__); > > > - return -ENOMEM; > > > - } > > > > I think this order change will cause a functional change because > > pci_allocate_vc_save_buffers() only allocated for those capabilities that > > are exist for dev. Thus, the loop will prematurely exit. > > Oof, thank you for catching this! I'll drop this for now. > > It would be nice to make pci_save_vc_state() parallel with > pci_restore_vc_state() (and with most other pci_save_*_state() > functions) and have it return void. But pci_save_state() returns the > pci_save_vc_state() return value, and there are ~20 pci_save_state() > callers that pay attention to that return value. > > I'm not convinced there's real value in pci_save_state() error > returns, given that so few callers check it, but it definitely > requires more analysis before removing it. Indeed, I also though that -ENOMEM even in the original is questionable. These are not the real sources of the failure but just secondary effect from the failure that occurred earlier in _pci_add_cap_save_buffer().
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 869d204a70a3..503376bf7e75 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1686,10 +1686,8 @@ static int pci_save_pcie_state(struct pci_dev *dev) return 0; save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP); - if (!save_state) { - pci_err(dev, "buffer not found in %s\n", __func__); + if (!save_state) return -ENOMEM; - } cap = (u16 *)&save_state->cap.data[0]; pcie_capability_read_word(dev, PCI_EXP_DEVCTL, &cap[i++]); @@ -1742,19 +1740,17 @@ static void pci_restore_pcie_state(struct pci_dev *dev) static int pci_save_pcix_state(struct pci_dev *dev) { - int pos; struct pci_cap_saved_state *save_state; + u8 pos; + + save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX); + if (!save_state) + return -ENOMEM; pos = pci_find_capability(dev, PCI_CAP_ID_PCIX); if (!pos) return 0; - save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX); - if (!save_state) { - pci_err(dev, "buffer not found in %s\n", __func__); - return -ENOMEM; - } - pci_read_config_word(dev, pos + PCI_X_CMD, (u16 *)save_state->cap.data); @@ -1763,14 +1759,19 @@ static int pci_save_pcix_state(struct pci_dev *dev) static void pci_restore_pcix_state(struct pci_dev *dev) { - int i = 0, pos; struct pci_cap_saved_state *save_state; + u8 pos; + int i = 0; u16 *cap; save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX); - pos = pci_find_capability(dev, PCI_CAP_ID_PCIX); - if (!save_state || !pos) + if (!save_state) return; + + pos = pci_find_capability(dev, PCI_CAP_ID_PCIX); + if (!pos) + return; + cap = (u16 *)&save_state->cap.data[0]; pci_write_config_word(dev, pos + PCI_X_CMD, cap[i++]); diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index e0bc90597dca..007e4a082e6f 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -35,16 +35,14 @@ void pci_save_ltr_state(struct pci_dev *dev) if (!pci_is_pcie(dev)) return; + save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR); + if (!save_state) + return; + ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR); if (!ltr) return; - save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR); - if (!save_state) { - pci_err(dev, "no suspend buffer for LTR; ASPM issues possible after resume\n"); - return; - } - /* Some broken devices only support dword access to LTR */ cap = &save_state->cap.data[0]; pci_read_config_dword(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, cap); @@ -57,8 +55,11 @@ void pci_restore_ltr_state(struct pci_dev *dev) u32 *cap; save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR); + if (!save_state) + return; + ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR); - if (!save_state || !ltr) + if (!ltr) return; /* Some broken devices only support dword access to LTR */ diff --git a/drivers/pci/vc.c b/drivers/pci/vc.c index a4ff7f5f66dd..c39f3be518d4 100644 --- a/drivers/pci/vc.c +++ b/drivers/pci/vc.c @@ -355,20 +355,17 @@ int pci_save_vc_state(struct pci_dev *dev) int i; for (i = 0; i < ARRAY_SIZE(vc_caps); i++) { - int pos, ret; struct pci_cap_saved_state *save_state; + int pos, ret; + + save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); + if (!save_state) + return -ENOMEM; pos = pci_find_ext_capability(dev, vc_caps[i].id); if (!pos) continue; - save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); - if (!save_state) { - pci_err(dev, "%s buffer not found in %s\n", - vc_caps[i].name, __func__); - return -ENOMEM; - } - ret = pci_vc_do_save_buffer(dev, pos, save_state, true); if (ret) { pci_err(dev, "%s save unsuccessful %s\n", @@ -392,12 +389,15 @@ void pci_restore_vc_state(struct pci_dev *dev) int i; for (i = 0; i < ARRAY_SIZE(vc_caps); i++) { - int pos; struct pci_cap_saved_state *save_state; + int pos; + + save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); + if (!save_state) + continue; pos = pci_find_ext_capability(dev, vc_caps[i].id); - save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id); - if (!save_state || !pos) + if (!pos) continue; pci_vc_do_save_buffer(dev, pos, save_state, false);