| Message ID | f51768aa-8e8d-65e0-497c-eda1741e8a0a@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | PCI/ASPM: Reject sysfs attempts to enable states that are not covered by policy | expand |
On Mon, Jul 20, 2020 at 08:08:59AM +0200, Heiner Kallweit wrote: > When trying to enable a state that is not covered by the policy, > then the change request will be silently ignored. That's not too > nice to the user, therefore reject such attempts explicitly. > > Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> > --- > drivers/pci/pcie/aspm.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > index b17e5ffd3..cd0f30ca9 100644 > --- a/drivers/pci/pcie/aspm.c > +++ b/drivers/pci/pcie/aspm.c > @@ -1224,11 +1224,16 @@ static ssize_t aspm_attr_store_common(struct device *dev, > { > struct pci_dev *pdev = to_pci_dev(dev); > struct pcie_link_state *link = pcie_aspm_get_link(pdev); > + u32 policy_state = policy_to_aspm_state(link); > bool state_enable; > > if (strtobool(buf, &state_enable) < 0) > return -EINVAL; > > + /* reject attempts to enable states not covered by policy */ > + if (state_enable && state & ~policy_state) > + return -EPERM; I really like the sentiment of this patch, but I don't like the fact that this test for states being covered by the policy is here by itself. There must be some place in the pcie_config_aspm_link() path that does a similar test and silently ignores things not covered by the policy? If we could take advantage of *that* test, we won't have to worry about things getting out of sync if we change that test in the future. Maybe pcie_config_aspm_link() could return -EPERM if the policy doesn't allow the requested state, and we could just notice that here? > down_read(&pci_bus_sem); > mutex_lock(&aspm_lock); > > @@ -1241,7 +1246,7 @@ static ssize_t aspm_attr_store_common(struct device *dev, > link->aspm_disable |= state; > } > > - pcie_config_aspm_link(link, policy_to_aspm_state(link)); > + pcie_config_aspm_link(link, policy_state); > > mutex_unlock(&aspm_lock); > up_read(&pci_bus_sem); > -- > 2.27.0 >
Am 09.09.2020 um 20:28 schrieb Bjorn Helgaas: > On Mon, Jul 20, 2020 at 08:08:59AM +0200, Heiner Kallweit wrote: >> When trying to enable a state that is not covered by the policy, >> then the change request will be silently ignored. That's not too >> nice to the user, therefore reject such attempts explicitly. >> >> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> >> --- >> drivers/pci/pcie/aspm.c | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c >> index b17e5ffd3..cd0f30ca9 100644 >> --- a/drivers/pci/pcie/aspm.c >> +++ b/drivers/pci/pcie/aspm.c >> @@ -1224,11 +1224,16 @@ static ssize_t aspm_attr_store_common(struct device *dev, >> { >> struct pci_dev *pdev = to_pci_dev(dev); >> struct pcie_link_state *link = pcie_aspm_get_link(pdev); >> + u32 policy_state = policy_to_aspm_state(link); >> bool state_enable; >> >> if (strtobool(buf, &state_enable) < 0) >> return -EINVAL; >> >> + /* reject attempts to enable states not covered by policy */ >> + if (state_enable && state & ~policy_state) >> + return -EPERM; > > I really like the sentiment of this patch, but I don't like the fact > that this test for states being covered by the policy is here by > itself. > > There must be some place in the pcie_config_aspm_link() path that does > a similar test and silently ignores things not covered by the policy? > If we could take advantage of *that* test, we won't have to worry > about things getting out of sync if we change that test in the future. > > Maybe pcie_config_aspm_link() could return -EPERM if the policy > doesn't allow the requested state, and we could just notice that here? > Oh, I just see that I missed to follow-up on this topic. Currently pcie_config_aspm_link() is called in two versions: 1. with state argument 0 2. with state argument policy_to_aspm_state(link) Therefore pcie_config_aspm_link() doesn't check for states not covered by the policy. We could add a policy check, but the only use case where this check would be needed is the call from aspm_attr_store_common(). Is this worth it? Ot better go with the check in aspm_attr_store_common() as proposed? In addition, based on the two types of calls to pcie_config_aspm_link(), we could simplify usage of this function and replace the state argument with a bool enable flag. If set, then pcie_config_aspm_link() would internally select policy_to_aspm_state() as requested state. >> down_read(&pci_bus_sem); >> mutex_lock(&aspm_lock); >> >> @@ -1241,7 +1246,7 @@ static ssize_t aspm_attr_store_common(struct device *dev, >> link->aspm_disable |= state; >> } >> >> - pcie_config_aspm_link(link, policy_to_aspm_state(link)); >> + pcie_config_aspm_link(link, policy_state); >> >> mutex_unlock(&aspm_lock); >> up_read(&pci_bus_sem); >> -- >> 2.27.0 >>
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index b17e5ffd3..cd0f30ca9 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -1224,11 +1224,16 @@ static ssize_t aspm_attr_store_common(struct device *dev, { struct pci_dev *pdev = to_pci_dev(dev); struct pcie_link_state *link = pcie_aspm_get_link(pdev); + u32 policy_state = policy_to_aspm_state(link); bool state_enable; if (strtobool(buf, &state_enable) < 0) return -EINVAL; + /* reject attempts to enable states not covered by policy */ + if (state_enable && state & ~policy_state) + return -EPERM; + down_read(&pci_bus_sem); mutex_lock(&aspm_lock); @@ -1241,7 +1246,7 @@ static ssize_t aspm_attr_store_common(struct device *dev, link->aspm_disable |= state; } - pcie_config_aspm_link(link, policy_to_aspm_state(link)); + pcie_config_aspm_link(link, policy_state); mutex_unlock(&aspm_lock); up_read(&pci_bus_sem);
When trying to enable a state that is not covered by the policy, then the change request will be silently ignored. That's not too nice to the user, therefore reject such attempts explicitly. Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> --- drivers/pci/pcie/aspm.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)