linux-kernel - [PATCH] PCI: Release coalesced resource

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Message-ID: <20230525153248.712779-1-ross.lagerwall@citrix.com>
Date:   Thu, 25 May 2023 16:32:48 +0100
From:   Ross Lagerwall <ross.lagerwall@...rix.com>
To:     <linux-pci@...r.kernel.org>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        <linux-kernel@...r.kernel.org>,
        Ross Lagerwall <ross.lagerwall@...rix.com>
Subject: [PATCH] PCI: Release coalesced resource

When contiguous windows are coalesced, the resource is invalidated and
consequently not added to the bus. However, it remains in the resource
hierarchy:

...
  ef2fff00-ef2fffff : 0000:00:13.2
    ef2fff00-ef2fffff : ehci_hcd
00000000-00000000 : PCI Bus 0000:00
f0000000-f3ffffff : PCI MMCONFIG 0000 [bus 00-3f]
  f0000000-f3ffffff : Reserved
...

In some cases (e.g. the Xen scratch region), this causes future calls to
allocate_resource() to choose an inappropriate location which the caller
cannot handle. Fix by releasing the resource and removing from the
hierarchy.

Fixes: 7c3855c423b1 ("PCI: Coalesce host bridge contiguous apertures")
Signed-off-by: Ross Lagerwall <ross.lagerwall@...rix.com>
---
 drivers/pci/probe.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 0b2826c4a832..00ed20ac0dd6 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -997,8 +997,10 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
 	resource_list_for_each_entry_safe(window, n, &resources) {
 		offset = window->offset;
 		res = window->res;
-		if (!res->flags && !res->start && !res->end)
+		if (!res->flags && !res->start && !res->end) {
+			release_resource(res);
 			continue;
+		}
 
 		list_move_tail(&window->node, &bridge->windows);
 
-- 
2.31.1