Re: [PATCH v13 15/15] PCI/CXL: Restore CXL state after CXL bus reset

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] cxl: HDM state restoration bypassed if SBR is natively unmasked
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commit 44f7ddf109a23fa1e25d7dc89752e3e7548f5c17
Author: Srirangan Madhavan <smadhavan@nvidia.com>

PCI/CXL: Restore CXL state after CXL bus reset

CXL bus reset can clear HDM decoder programming and CXL Device DVSEC
control state. Restore the cached state after a successful cxl_bus reset
while IOMMU exclusion remains active.

> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index dc57a202c91f7..6928c99aa7856 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
[ ... ]
> @@ -5015,6 +5015,7 @@ static int pci_reset_bus_function(struct pci_dev *dev, bool probe)
>  
>  static int cxl_reset_bus_function(struct pci_dev *dev, bool probe)
>  {
> +	struct cxl_hdm_info *snapshot __free(kfree) = NULL;

[Severity: High]
Will this new HDM state restoration logic be bypassed entirely if SBR is
natively unmasked?

Looking at pci_reset_fn_methods in drivers/pci/pci.c, "bus" is ordered
before "cxl_bus":

        { pci_reset_bus_function, .name = "bus" },
        { cxl_reset_bus_function, .name = "cxl_bus" },

When SBR is natively unmasked, pci_reset_bus_function() will succeed
during probe and will be placed before cxl_reset_bus_function() in the
device's reset_methods array. During a reset, __pci_reset_function_locked()
executes "bus" first. If "bus" succeeds and returns 0, it completely
bypasses "cxl_bus" and this newly added snapshot/restore logic.

Could this cause CXL HDM decoder state to be lost after a reset on these
devices?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260922083924.2451158-1-smadhavan@nvidia.com?part=15