Re: [PATCH v9 09/11] PCI/CXL: Expose CXL Reset as a PCI reset method

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The CXL reset method skips function-scoped validation during execution, relying entirely on a flawed probe-time check that occurs before sibling functions are added to the PCI bus.
--

--- Patch [9]: [PATCH v9 09/11] PCI/CXL: Expose CXL Reset as a PCI reset method ---
commit f2ff500e92a2699aaf86703b4ef5bcf21ad27f7b
Author: Srirangan Madhavan <smadhavan@nvidia.com>

PCI/CXL: Expose CXL Reset as a PCI reset method

Add the CXL Reset helper to the PCI reset-method table so userspace can
select it through the existing reset_method ABI. Advertise the method for
Type 2 CXL devices that report CXL Reset support in the CXL Device DVSEC.

> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 77b17b13ee615..ef25ba5f7fe95 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
[ ... ]
> @@ -5092,6 +5093,7 @@ const struct pci_reset_fn_method pci_reset_fn_methods[] = {
>  	{ },
>  	{ pci_dev_specific_reset, .name = "device_specific" },
>  	{ pci_dev_acpi_reset, .name = "acpi" },
> +	{ cxl_reset_function, .name = "cxl_reset" },

[Severity: High]
Does adding this reset method here introduce a regression where multi-function
CXL devices are exposed to state corruption when a reset is triggered?

During early system boot, PCI enumeration calls pci_init_reset_methods()
which evaluates this method with probe = true. The method then calls
cxl_reset_validate_function_scoped() to walk the bus looking for siblings:

drivers/cxl/core/reset.c:cxl_reset_validate_function_scoped() {
    ...
    pci_walk_bus(pdev->bus, cxl_reset_validate_function_scope, &wctx);
    ...
}

Because function 0 has not yet been added to the bus list at this early stage
and sibling functions have not been scanned, the bus walk is empty. The reset
method is then incorrectly recorded as valid for function 0.

When the reset is actually executed later via VFIO or sysfs,
cxl_reset_function() is called with probe = false. This skips the validation:

drivers/cxl/core/reset.c:cxl_reset_function() {
    ...
    if (probe)
        return cxl_reset_validate_function_scoped(&ctx);
    ...
}

This means the bus is not re-evaluated when the siblings are actually present.
Will this proceed to reset the entire device without isolating sibling
functions, resulting in corrupted or lost state for those siblings?

>  	{ pcie_reset_flr, .name = "flr" },

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260709010304.680422-1-smadhavan@nvidia.com?part=9