On Wed, 21 Feb 2024 09:31:10 -0800
Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> Jonathan Cameron wrote:
> > 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?
>
> True, that can go.
>
> > > - 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); ...
>
> True, there's enough here to do an even deeper cleanup... below.
>
> >
> >
> > > - }
> > > - 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?
>
> Yeah, I will switch to this since the previous state was also skipping
> the debug messages on success.
>
> Follow-on cleanup:
>
> -- 8< --
> From e30c267c0b69d5e4531d8f65ec86e4fa32d72340 Mon Sep 17 00:00:00 2001
> From: Dan Williams <dan.j.williams@xxxxxxxxx>
> Date: Tue, 20 Feb 2024 22:44:34 -0800
> Subject: [PATCH] cxl/acpi: Cleanup __cxl_parse_cfmws() error exits
>
> As a follow on to the recent rework of __cxl_parse_cfmws() to always
> return errors, use cleanup.h helpers to remove goto and other cleanups
> now that logging is moved to the cxl_parse_cfmws() wrapper.
This runs into the question of where the declarations should be for
cleanup.h changes. I can dig out the Linus comment on this but
I'm feeling lazy ;)
In general I like this stuff, but in this case I think it's ended
up harder to read than the original code.
>
> Reported-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Closes: http://lore.kernel.org/r/20240219124041.00002bda@xxxxxxxxxx
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
> drivers/cxl/acpi.c | 45 +++++++++++++++++++--------------------------
> 1 file changed, 19 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 1a3e6aafbdcc..b1ea2d152c65 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -319,25 +319,23 @@ static const struct cxl_root_ops acpi_root_ops = {
> static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
> struct cxl_cfmws_context *ctx)
> {
> + struct device *cxld_dev __free(put_device) = NULL;
> int target_map[CXL_DECODER_MAX_INTERLEAVE];
> struct cxl_port *root_port = ctx->root_port;
> + struct resource *res __free(kfree) = NULL;
> struct resource *cxl_res = ctx->cxl_res;
> + const char *name __free(kfree) = NULL;
Linus has expressed that he prefers these done inline
so the allocation and clearing are obviously associated - there
is an ordering related factor as well as they will unwind
in the reverse of declaration order, not allocation order.
> struct cxl_cxims_context cxims_ctx;
> struct cxl_root_decoder *cxlrd;
> struct device *dev = ctx->dev;
> cxl_calc_hb_fn cxl_calc_hb;
> struct cxl_decoder *cxld;
> unsigned int ways, i, ig;
> - struct resource *res;
> int rc;
>
> 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);
> + if (rc)
> return rc;
> - }
>
> rc = eiw_to_ways(cfmws->interleave_ways, &ways);
> if (rc)
> @@ -352,10 +350,11 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
> if (!res)
> return -ENOMEM;
>
> - res->name = kasprintf(GFP_KERNEL, "CXL Window %d", ctx->id++);
> - if (!res->name)
> - goto err_name;
const char *name __free(kfree) = kasprintf(...);
same for the others.
> + name = kasprintf(GFP_KERNEL, "CXL Window %d", ctx->id++);
> + if (!name)
> + return -ENOMEM;
>
> + res->name = name;
> res->start = cfmws->base_hpa;
> res->end = cfmws->base_hpa + cfmws->window_size - 1;
> res->flags = IORESOURCE_MEM;
> @@ -363,7 +362,9 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
> /* add to the local resource tracking to establish a sort order */
> rc = insert_resource(cxl_res, res);
> if (rc)
> - goto err_insert;
> + return rc;
> + name = NULL;
I guess we'll get used to this. Kind of annoying that no_free_ptr() is
defined as __must_check. Otherwise would be good to use that to document
the 'why' of these are being set to NULL.
> + res = NULL;
>
> if (cfmws->interleave_arithmetic == ACPI_CEDT_CFMWS_ARITHMETIC_MODULO)
> cxl_calc_hb = cxl_hb_modulo;
> @@ -375,11 +376,12 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
> return PTR_ERR(cxlrd);
>
> cxld = &cxlrd->cxlsd.cxld;
> + cxld_dev = &cxld->dev;
This I find odd, there is no allocation as such in here so the matching of
the unwind and the allocation isn't clear.
> cxld->flags = cfmws_to_decoder_flags(cfmws->restrictions);
> cxld->target_type = CXL_DECODER_HOSTONLYMEM;
> cxld->hpa_range = (struct range) {
> - .start = res->start,
> - .end = res->end,
> + .start = cfmws->base_hpa,
> + .end = cfmws->base_hpa + cfmws->window_size - 1,
> };
> cxld->interleave_ways = ways;
> /*
> @@ -399,11 +401,10 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
> rc = acpi_table_parse_cedt(ACPI_CEDT_TYPE_CXIMS,
> cxl_parse_cxims, &cxims_ctx);
> if (rc < 0)
> - goto err_xormap;
> + return rc;
> if (!cxlrd->platform_data) {
> dev_err(dev, "No CXIMS for HBIG %u\n", ig);
> - rc = -EINVAL;
> - goto err_xormap;
> + return -EINVAL;
> }
> }
> }
> @@ -411,18 +412,10 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
> cxlrd->qos_class = cfmws->qtg_id;
>
> rc = cxl_decoder_add(cxld, target_map);
> -err_xormap:
> if (rc)
> - put_device(&cxld->dev);
> - else
> - rc = cxl_decoder_autoremove(dev, cxld);
> - return rc;
> -
> -err_insert:
> - kfree(res->name);
> -err_name:
> - kfree(res);
> - return -ENOMEM;
> + return rc;
> + cxld_dev = NULL;
This is definitely not nice to read. We are randomly setting an
apparently unrelated pointer to NULL. At very least the __free
should operating on cxld then we can use
return cxl_decoder_autoremove(dev, no_free_ptr(cxld));
But the get was burred in cxl_root_decoder_alloc() so even that
is non obvious. You could do the magic to make
struct cxl_root_decoder *cxld __free(cxlroot_put) =
cxl_root_decoder_alloc(root_port, ways, cxl_calc_hb);
return cxl_decoder_autoremove(dev, &no_free_ptr(cxlrd)->cxlsd.cxld);
Is it worth it? Just about, maybe...
> + return cxl_decoder_autoremove(dev, cxld);
> }
>
> static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
