On Mon, Jun 30, 2025 at 05:26:39PM +0300, Ilpo Järvinen wrote:
> When using relaxed tail alignment for the bridge window,
> pbus_size_mem() also tries to minimize min_align, which can under
> certain scenarios end up increasing min_align from that found by
> calculate_mem_align().
>
> Ensure min_align is not increased by the relaxed tail alignment.
>
> Eventually, it would be better to add calculate_relaxed_head_align()
> similar to calculate_mem_align() which finds out what alignment can be
> used for the head without introducing any gaps into the bridge window
> to give flexibility on head address too. But that looks relatively
> complex algorithm so it requires much more testing than fixing the
> immediate problem causing a regression.
>
> Fixes: 67f9085596ee ("PCI: Allow relaxed bridge window tail sizing for optional resources")
> Reported-by: Rio <rio@xxxxxx>
Was there a regression report URL we could include here?
> Tested-by: Rio <rio@xxxxxx>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> ---
> drivers/pci/setup-bus.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 07c3d021a47e..f90d49cd07da 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1169,6 +1169,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> resource_size_t children_add_size = 0;
> resource_size_t children_add_align = 0;
> resource_size_t add_align = 0;
> + resource_size_t relaxed_align;
>
> if (!b_res)
> return -ENOSPC;
> @@ -1246,8 +1247,9 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> if (bus->self && size0 &&
> !pbus_upstream_space_available(bus, mask | IORESOURCE_PREFETCH, type,
> size0, min_align)) {
> - min_align = 1ULL << (max_order + __ffs(SZ_1M));
> - min_align = max(min_align, win_align);
> + relaxed_align = 1ULL << (max_order + __ffs(SZ_1M));
> + relaxed_align = max(relaxed_align, win_align);
> + min_align = min(min_align, relaxed_align);
> size0 = calculate_memsize(size, min_size, 0, 0, resource_size(b_res), win_align);
> pci_info(bus->self, "bridge window %pR to %pR requires relaxed alignment rules\n",
> b_res, &bus->busn_res);
> @@ -1261,8 +1263,9 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> if (bus->self && size1 &&
> !pbus_upstream_space_available(bus, mask | IORESOURCE_PREFETCH, type,
> size1, add_align)) {
> - min_align = 1ULL << (max_order + __ffs(SZ_1M));
> - min_align = max(min_align, win_align);
> + relaxed_align = 1ULL << (max_order + __ffs(SZ_1M));
> + relaxed_align = max(min_align, win_align);
> + min_align = min(min_align, relaxed_align);
> size1 = calculate_memsize(size, min_size, add_size, children_add_size,
> resource_size(b_res), win_align);
> pci_info(bus->self,
> --
> 2.39.5
>
