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@xxxxxxxxx>
> ---
> 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
>
