Re: [PATCH v2 1/2] PCI: endpoint: Skip upper halves of 64-bit BARs during search

[Niklas Cassel]

On Mon, Nov 02, 2026 at 04:53:05PM +0530, Manikanta Maddireddy wrote:
> pci_epc_get_next_free_bar() skips the upper half of a 64-bit BAR only
> when it is the starting BAR. If the search subsequently passes a
> reserved or disabled 64-bit BAR, it can return its upper half as an
> independent BAR because that slot has a default programmable descriptor.
> 
> For example, Tegra exposes a programmable 64-bit BAR0 and reserved
> 64-bit BAR2 and BAR4. A search starting at BAR1 skips BAR1 and BAR2,
> then incorrectly returns BAR3. The next search can similarly return
> BAR5, causing the EPF test driver to allocate and program BARs that
> belong to the reserved hardware windows.
> 
> Check each candidate's preceding descriptor inside the search loop so
> upper halves are skipped throughout the search. With the Tegra layout,
> BAR0 is the only available BAR and subsequent searches return NO_BAR.
> 
> Fixes: 27ce1d8ecb9b ("PCI: endpoint: Allow only_64bit on BAR_RESERVED")
> Signed-off-by: Manikanta Maddireddy <mmaddireddy@xxxxxxxxxx>

Reviewed-by: Niklas Cassel <cassel@xxxxxxxxxx>