Re: [PATCH] [HACK] drop zen5_init checks due to segfault

Robert Richter
2025-06-24T05:43:29Z

On 17.06.25 13:33:18, Joshua Hahn wrote:
> I was hoping for some help in understanding your explanation here -- I don't
> think I can see where the dependency appears. (In particular, I'm having
> trouble understanding where the efi_rts_wq dependnecy matters during the
> cxl_zen5_init function).

Here a temporary patch with an explanation in the description:

From a540b814d48574b67a9aaa97a5d7536c61d4deda Mon Sep 17 00:00:00 2001
From: Robert Richter <rrichter@amd.com>
Date: Tue, 13 May 2025 15:02:16 +0200
Subject: [PATCH] cxl/acpi: Prepare use of EFI runtime services

In order to use EFI runtime services, esp. ACPI PRM which uses the
efi_rts_wq workqueue, initialize EFI before CXL ACPI.

There is a subsys_initcall order dependency if driver is builtin:

subsys_initcall(cxl_acpi_init);
subsys_initcall(efisubsys_init);

Prevent the efi_rts_wq workqueue being used by cxl_acpi_init() before
its allocation. Use subsys_initcall_sync(cxl_acpi_init) to always run
efisubsys_init() first.

Reported-by: Gregory Price <gourry@gourry.net>
Signed-off-by: Robert Richter <rrichter@amd.com>
---
drivers/cxl/acpi.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index a1a99ec3f12c..af750a8bd373 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -932,8 +932,12 @@ static void __exit cxl_acpi_exit(void)
cxl_bus_drain();
}

-/* load before dax_hmem sees 'Soft Reserved' CXL ranges */
-subsys_initcall(cxl_acpi_init);
+/*
+ * Load before dax_hmem sees 'Soft Reserved' CXL ranges. Use
+ * subsys_initcall_sync() since there is an order dependency with
+ * subsys_initcall(efisubsys_init), which must run first.
+ */
+subsys_initcall_sync(cxl_acpi_init);

/*
* Arrange for host-bridge ports to be active synchronous with
--
2.39.5