Re: [PATCH] testing/cxl: Fix abused pci_bus_read_config_word() on platform device

[Alison Schofield]

On Wed, Oct 16, 2024 at 09:52:13AM +0800, Li Zhijian wrote:
> The cxl_region_shared_upstream_bandwidth_update() in clx_core works on
> PCI/PCIe CXL device only while cxl_test was implemeneted by platform
> device.
> 
> Mock a cxl_region_shared_upstream_bandwidth_update() which does nothing
> for cxl_core so that the cxl_test goes well.
> 
> Abuse cxl_region_shared_upstream_bandwidth_update() on platform device
> will cause a kernel panic with calltrace:

snip

> ---
>  tools/testing/cxl/Kbuild      | 2 ++
>  tools/testing/cxl/mock_cdat.c | 8 ++++++++
>  2 files changed, 10 insertions(+)
>  create mode 100644 tools/testing/cxl/mock_cdat.c
> 
> diff --git a/tools/testing/cxl/Kbuild b/tools/testing/cxl/Kbuild
> index b1256fee3567..ed9f50dee3f5 100644
> --- a/tools/testing/cxl/Kbuild
> +++ b/tools/testing/cxl/Kbuild
> @@ -15,6 +15,7 @@ ldflags-y += --wrap=devm_cxl_add_rch_dport
>  ldflags-y += --wrap=cxl_rcd_component_reg_phys
>  ldflags-y += --wrap=cxl_endpoint_parse_cdat
>  ldflags-y += --wrap=cxl_dport_init_ras_reporting
> +ldflags-y += --wrap=cxl_region_shared_upstream_bandwidth_update
>  
>  DRIVERS := ../../../drivers
>  CXL_SRC := $(DRIVERS)/cxl
> @@ -61,6 +62,7 @@ cxl_core-y += $(CXL_CORE_SRC)/pci.o
>  cxl_core-y += $(CXL_CORE_SRC)/hdm.o
>  cxl_core-y += $(CXL_CORE_SRC)/pmu.o
>  cxl_core-y += $(CXL_CORE_SRC)/cdat.o
> +cxl_core-y += mock_cdat.o
>  cxl_core-$(CONFIG_TRACING) += $(CXL_CORE_SRC)/trace.o
>  cxl_core-$(CONFIG_CXL_REGION) += $(CXL_CORE_SRC)/region.o
>  cxl_core-y += config_check.o
> diff --git a/tools/testing/cxl/mock_cdat.c b/tools/testing/cxl/mock_cdat.c
> new file mode 100644
> index 000000000000..99974153b3f6
> --- /dev/null
> +++ b/tools/testing/cxl/mock_cdat.c
> @@ -0,0 +1,8 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2024 FUJITSU LIMITED. All rights reserved. */
> +
> +#include <cxl.h>
> +
> +void __wrap_cxl_region_shared_upstream_bandwidth_update(struct cxl_region *cxlr)
> +{
> +}

The addition of file mock_cdat.c made me wonder why this wrapper couldn't join
all the other __wrap's defined in test/mock.c. I tried, as you probably did,
and see the circular dependency. I mention it here in case anyone else has a
way to simplify this.

Otherwise LGTM:
Reviewed-by: Alison Schofield <alison.schofield@xxxxxxxxx>



> -- 
> 2.44.0
>