On Sat, 17 Feb 2024 12:29:32 -0800
Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> The expectation is that cxl_parse_cfwms() continues in the face the of
> failure as evidenced by code like:
>
> cxlrd = cxl_root_decoder_alloc(root_port, ways, cxl_calc_hb);
> if (IS_ERR(cxlrd))
> return 0;
>
> There are other error paths in that function which mistakenly follow
> idiomatic expectations and return an error when they should not. Most of
> those mistakes are innocuous checks that hardly ever fail in practice.
> However, a recent change succeed in making the implementation more
> fragile by applying an idiomatic, but still wrong "fix" [1]. In this
> failure case the kernel reports:
>
> cxl root0: Failed to populate active decoder targets
> cxl_acpi ACPI0017:00: Failed to add decode range: [mem 0x00000000-0x7fffffff flags 0x200]
>
> ...which is a real issue with that one window (to be fixed separately),
> but ends up failing the entirety of cxl_acpi_probe().
>
> Undo that recent breakage while also removing the confusion about
> ignoring errors. Update all exits paths to return an error per typical
> expectations and let an outer wrapper function handle dropping the
> error.
>
> Fixes: 91019b5bc7c2 ("cxl/acpi: Return 'rc' instead of '0' in cxl_parse_cfmws()") [1]
> Cc: <stable@xxxxxxxxxxxxxxx>
> Cc: Breno Leitao <leitao@xxxxxxxxxx>
> Cc: Alison Schofield <alison.schofield@xxxxxxxxx>
> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
General idea makes a lot of sense to me.
A few comments on specific implementation inline
> ---
> drivers/cxl/acpi.c | 45 +++++++++++++++++++++++++++------------------
> 1 file changed, 27 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index dcf2b39e1048..53d2dff0c7a3 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -316,31 +316,27 @@ static const struct cxl_root_ops acpi_root_ops = {
> .qos_class = cxl_acpi_qos_class,
> };
>
> -static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
> - const unsigned long end)
> +static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
> + struct cxl_cfmws_context *ctx)
> {
> int target_map[CXL_DECODER_MAX_INTERLEAVE];
> - struct cxl_cfmws_context *ctx = arg;
> struct cxl_port *root_port = ctx->root_port;
> struct resource *cxl_res = ctx->cxl_res;
> struct cxl_cxims_context cxims_ctx;
> struct cxl_root_decoder *cxlrd;
> struct device *dev = ctx->dev;
> - struct acpi_cedt_cfmws *cfmws;
> cxl_calc_hb_fn cxl_calc_hb;
> struct cxl_decoder *cxld;
> unsigned int ways, i, ig;
> struct resource *res;
> int rc;
>
> - cfmws = (struct acpi_cedt_cfmws *) header;
> -
> rc = cxl_acpi_cfmws_verify(dev, cfmws);
> if (rc) {
> dev_err(dev, "CFMWS range %#llx-%#llx not registered\n",
> cfmws->base_hpa,
> cfmws->base_hpa + cfmws->window_size - 1);
Why keep this error print?
> - return 0;
> + return rc;
> }
>
> rc = eiw_to_ways(cfmws->interleave_ways, &ways);
> @@ -376,7 +372,7 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
>
> cxlrd = cxl_root_decoder_alloc(root_port, ways, cxl_calc_hb);
> if (IS_ERR(cxlrd))
> - return 0;
> + return PTR_ERR(cxlrd);
>
> cxld = &cxlrd->cxlsd.cxld;
> cxld->flags = cfmws_to_decoder_flags(cfmws->restrictions);
> @@ -420,16 +416,7 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
> put_device(&cxld->dev);
> else
> rc = cxl_decoder_autoremove(dev, cxld);
> - if (rc) {
> - dev_err(dev, "Failed to add decode range: %pr", res);
> - return rc;
As no longer sharing this message. Might be neater to have this lot as
rc = cxl_decoder_add(cxld, target_map);
err_xormap:
if (rc) {
put_device(&cxld->dev);
return rc;
}
return cxl_decoder_autoremove(dev, cxld);
or a second error exit path.
rc = cxl_decoder_add(cxld, target_map);
if (rc)
goto err_put_devie;
return cxl_decoder_autoremove(dev, cxld;
err_put_device;
put_device(&cxld->dev);
return rc;
err_insert:
kfree(res->name); ...
> - }
> - dev_dbg(dev, "add: %s node: %d range [%#llx - %#llx]\n",
> - dev_name(&cxld->dev),
> - phys_to_target_node(cxld->hpa_range.start),
> - cxld->hpa_range.start, cxld->hpa_range.end);
> -
> - return 0;
> + return rc;
>
> err_insert:
> kfree(res->name);
> @@ -438,6 +425,28 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
> return -ENOMEM;
> }
>
> +static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
> + const unsigned long end)
> +{
> + struct acpi_cedt_cfmws *cfmws = (struct acpi_cedt_cfmws *)header;
> + struct cxl_cfmws_context *ctx = arg;
> + struct device *dev = ctx->dev;
> + int rc;
> +
> + dev_dbg(dev, "decode range: node: %d range [%#llx - %#llx]\n",
> + phys_to_target_node(cfmws->base_hpa), cfmws->base_hpa,
> + cfmws->base_hpa + cfmws->window_size - 1);
Could maybe put this in an else below?
> + rc = __cxl_parse_cfmws(cfmws, ctx);
> + if (rc)
> + dev_err(dev,
> + "Failed to add decode range: [%#llx - %#llx] (%d)\n",
> + cfmws->base_hpa,
> + cfmws->base_hpa + cfmws->window_size - 1, rc);
> +
else
dev_dbg();
so we only give the dbg version on success?
> + /* never fail cxl_acpi load for a single window failure */
> + return 0;
> +}
> +
> __mock struct acpi_device *to_cxl_host_bridge(struct device *host,
> struct device *dev)
> {
>
>
