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Message-ID: <442e5119dc4d2630b34d8cf9228c84b9cfee1717.camel@redhat.com>
Date: Fri, 14 Jun 2024 13:38:41 +0200
From: Philipp Stanner <pstanner@...hat.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Hans de Goede <hdegoede@...hat.com>, Maarten Lankhorst
<maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
Daniel Vetter <daniel@...ll.ch>, Bjorn Helgaas <bhelgaas@...gle.com>, Sam
Ravnborg <sam@...nborg.org>, dakr@...hat.com,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org
Subject: Re: [PATCH v9 00/13] Make PCI's devres API more consistent
On Thu, 2024-06-13 at 16:57 -0500, Bjorn Helgaas wrote:
> On Thu, Jun 13, 2024 at 01:50:13PM +0200, Philipp Stanner wrote:
> > Changes in v9:
> > - Remove forgotten dead code ('enabled' bit in struct pci_dev) in
> > patch No.8 ("Move pinned status bit...")
> > - Rework patch No.3:
> > - Change title from "Reimplement plural devres functions"
> > to "Add partial-BAR devres support".
> > - Drop excessive details about the general cleanup from the
> > commit
> > message. Only motivate why this patch's new infrastructure
> > is
> > necessary.
> > - Fix some minor spelling issues (s/pci/PCI ...)
> >
> > Changes in v8:
> > - Rebase the series on the already merged patches which were
> > slightly
> > modified by Bjorn Helgaas.
> > - Reword the pci_intx() commit message so it clearly states it's
> > about
> > reworking pci_intx().
> > - Move the removal of find_pci_dr() from patch "Remove legacy
> > pcim_release()" to patch "Give pci_intx() its own devres
> > callback"
> > since this later patch already removed all calls to that
> > function.
> > - In patch "Give pci_intx() its own devres callback": use
> > pci_is_enabled() (and, thus, the enabled_cnt in struct pci_dev)
> > instead of a separate enabled field. (Bjorn)
> >
> > Changes in v7:
> > - Split the entire series in smaller, more atomic chunks /
> > patches
> > (Bjorn)
> > - Remove functions (such as pcim_iomap_region_range()) that do
> > not yet
> > have a user (Bjorn)
> > - Don't export interfaces publicly anymore, except for
> > pcim_iomap_range(), needed by vboxvideo (Bjorn)
> > - Mention the actual (vboxvideo) bug in "PCI: Warn users..."
> > commit
> > (Bjorn)
> > - Drop docstring warnings on PCI-internal functions (Bjorn)
> > - Rework docstring warnings
> > - Fix spelling in a few places. Rewrapp paragraphs (Bjorn)
> >
> > Changes in v6:
> > - Restructure the cleanup in pcim_iomap_regions_request_all() so
> > that
> > it doesn't trigger a (false positive) test robot warning. No
> > behavior change intended. (Dan Carpenter)
> >
> > Changes in v5:
> > - Add Hans's Reviewed-by to vboxvideo patch (Hans de Goede)
> > - Remove stable-kernel from CC in vboxvideo patch (Hans de Goede)
> >
> > Changes in v4:
> > - Rebase against linux-next
> >
> > Changes in v3:
> > - Use the term "PCI devres API" at some forgotten places.
> > - Fix more grammar errors in patch #3.
> > - Remove the comment advising to call (the outdated) pcim_intx()
> > in pci.c
> > - Rename __pcim_request_region_range() flags-field "exclusive" to
> > "req_flags", since this is what the int actually represents.
> > - Remove the call to pcim_region_request() from patch #10. (Hans)
> >
> > Changes in v2:
> > - Make commit head lines congruent with PCI's style (Bjorn)
> > - Add missing error checks for devm_add_action(). (Andy)
> > - Repair the "Returns: " marks for docu generation (Andy)
> > - Initialize the addr_devres struct with memset(). (Andy)
> > - Make pcim_intx() a PCI-internal function so that new drivers
> > won't
> > be encouraged to use the outdated pci_intx() mechanism.
> > (Andy / Philipp)
> > - Fix grammar and spelling (Bjorn)
> > - Be more precise on why pcim_iomap_table() is problematic
> > (Bjorn)
> > - Provide the actual structs' and functions' names in the commit
> > messages (Bjorn)
> > - Remove redundant variable initializers (Andy)
> > - Regroup PM bitfield members in struct pci_dev (Andy)
> > - Make pcim_intx() visible only for the PCI subsystem so that
> > new
> > drivers won't use this outdated API (Andy, Myself)
> > - Add a NOTE to pcim_iomap() to warn about this function being
> > the one
> > exception that does just return NULL.
> > - Consistently use the term "PCI devres API"; also in Patch #10
> > (Bjorn)
> >
> >
> > ¡Hola!
> >
> > PCI's devres API suffers several weaknesses:
> >
> > 1. There are functions prefixed with pcim_. Those are always
> > managed
> > counterparts to never-managed functions prefixed with pci_ – or
> > so one
> > would like to think. There are some apparently unmanaged
> > functions
> > (all region-request / release functions, and pci_intx()) which
> > suddenly become managed once the user has initialized the device
> > with
> > pcim_enable_device() instead of pci_enable_device(). This
> > "sometimes
> > yes, sometimes no" nature of those functions is confusing and
> > therefore bug-provoking. In fact, it has already caused a bug in
> > DRM.
> > The last patch in this series fixes that bug.
> > 2. iomappings: Instead of giving each mapping its own callback, the
> > existing API uses a statically allocated struct tracking one
> > mapping
> > per bar. This is not extensible. Especially, you can't create
> > _ranged_ managed mappings that way, which many drivers want.
> > 3. Managed request functions only exist as "plural versions" with a
> > bit-mask as a parameter. That's quite over-engineered
> > considering
> > that each user only ever mapps one, maybe two bars.
> >
> > This series:
> > - add a set of new "singular" devres functions that use devres the
> > way
> > its intended, with one callback per resource.
> > - deprecates the existing iomap-table mechanism.
> > - deprecates the hybrid nature of pci_ functions.
> > - preserves backwards compatibility so that drivers using the
> > existing
> > API won't notice any changes.
> > - adds documentation, especially some warning users about the
> > complicated nature of PCI's devres.
> >
> >
> > Note that this series is based on my "unify pci_iounmap"-series
> > from a
> > few weeks ago. [1]
> >
> > I tested this on a x86 VM with a simple pci test-device with two
> > regions. Operates and reserves resources as intended on my system.
> > Kasan and kmemleak didn't find any problems.
> >
> > I believe this series cleans the API up as much as possible without
> > having to port all existing drivers to the new API. Especially, I
> > think
> > that this implementation is easy to extend if the need for new
> > managed
> > functions arises :)
> >
> > Greetings,
> > P.
> >
> > Philipp Stanner (13):
> > PCI: Add and use devres helper for bit masks
> > PCI: Add devres helpers for iomap table
> > PCI: Add partial-BAR devres support
> > PCI: Deprecate two surplus devres functions
> > PCI: Make devres region requests consistent
> > PCI: Warn users about complicated devres nature
> > PCI: Remove enabled status bit from pci_devres
> > PCI: Move pinned status bit to struct pci_dev
> > PCI: Give pcim_set_mwi() its own devres callback
> > PCI: Give pci_intx() its own devres callback
> > PCI: Remove legacy pcim_release()
> > PCI: Add pcim_iomap_range()
> > drm/vboxvideo: fix mapping leaks
> >
> > drivers/gpu/drm/vboxvideo/vbox_main.c | 20 +-
> > drivers/pci/devres.c | 903 +++++++++++++++++++++-
> > ----
> > drivers/pci/iomap.c | 16 +
> > drivers/pci/pci.c | 94 ++-
> > drivers/pci/pci.h | 23 +-
> > include/linux/pci.h | 5 +-
> > 6 files changed, 858 insertions(+), 203 deletions(-)
>
> This is on pci/devres with some commit log rework and the following
> diffs. I think the bar short/int thing is the only actual code
> change. Happy to squash in any other updates or things I botched.
I looked through your tree and only found the following nit:
In commit "PCI: Remove struct pci_devres.enabled status bit" you
changed the line
"The PCI devres implementation has a separate boolean to track whether
a"
to:
"The pci_devres struct has a separate boolean to track whether a device
is"
In past reviews that has been criticized and I was told to always call
it "struct pci_devres", not the other way around. That's also how it's
put in the following paragraph.
>
> Planned for v6.11.
\o/
P.
>
> diff --git a/drivers/pci/devres.c b/drivers/pci/devres.c
> index 2f0379a4e58f..d9b78a0d903a 100644
> --- a/drivers/pci/devres.c
> +++ b/drivers/pci/devres.c
> @@ -11,7 +11,7 @@
> * 1. It is very strongly tied to the statically allocated mapping
> table in
> * struct pcim_iomap_devres below. This is mostly solved in the
> sense of the
> * pcim_ functions in this file providing things like ranged
> mapping by
> - * bypassing this table, wheras the functions that were present
> in the old
> + * bypassing this table, whereas the functions that were present
> in the old
> * API still enter the mapping addresses into the table for users
> of the old
> * API.
> *
> @@ -25,10 +25,11 @@
> * Consequently, in the new API, region requests performed by the
> pcim_
> * functions are automatically cleaned up through the devres
> callback
> * pcim_addr_resource_release().
> - * Users utilizing pcim_enable_device() + pci_*region*() are
> redirected in
> + *
> + * Users of pcim_enable_device() + pci_*region*() are redirected
> in
> * pci.c to the managed functions here in this file. This isn't
> exactly
> - * perfect, but the only alternative way would be to port ALL
> drivers using
> - * said combination to pcim_ functions.
> + * perfect, but the only alternative way would be to port ALL
> drivers
> + * using said combination to pcim_ functions.
> *
> * TODO:
> * Remove the legacy table entirely once all calls to
> pcim_iomap_table() in
> @@ -42,7 +43,7 @@ struct pcim_iomap_devres {
> void __iomem *table[PCI_STD_NUM_BARS];
> };
>
> -/* Used to restore the old intx state on driver detach. */
> +/* Used to restore the old INTx state on driver detach. */
> struct pcim_intx_devres {
> int orig_intx;
> };
> @@ -77,7 +78,7 @@ struct pcim_addr_devres {
> void __iomem *baseaddr;
> unsigned long offset;
> unsigned long len;
> - short bar;
> + int bar;
> };
>
> static inline void pcim_addr_devres_clear(struct pcim_addr_devres
> *res)
> @@ -108,8 +109,9 @@ static inline void pcim_addr_devres_clear(struct
> pcim_addr_devres *res)
> * Request a range within a device's PCI BAR. Sanity check the
> input.
> */
> static int __pcim_request_region_range(struct pci_dev *pdev, int
> bar,
> - unsigned long offset, unsigned long maxlen,
> - const char *name, int req_flags)
> + unsigned long offset,
> + unsigned long maxlen,
> + const char *name, int
> req_flags)
> {
> resource_size_t start = pci_resource_start(pdev, bar);
> resource_size_t len = pci_resource_len(pdev, bar);
> @@ -118,7 +120,7 @@ static int __pcim_request_region_range(struct
> pci_dev *pdev, int bar,
> if (start == 0 || len == 0) /* Unused BAR. */
> return 0;
> if (len <= offset)
> - return -EINVAL;
> + return -EINVAL;
>
> start += offset;
> len -= offset;
> @@ -141,7 +143,8 @@ static int __pcim_request_region_range(struct
> pci_dev *pdev, int bar,
> }
>
> static void __pcim_release_region_range(struct pci_dev *pdev, int
> bar,
> - unsigned long offset, unsigned long maxlen)
> + unsigned long offset,
> + unsigned long maxlen)
> {
> resource_size_t start = pci_resource_start(pdev, bar);
> resource_size_t len = pci_resource_len(pdev, bar);
> @@ -166,7 +169,7 @@ static void __pcim_release_region_range(struct
> pci_dev *pdev, int bar,
> }
>
> static int __pcim_request_region(struct pci_dev *pdev, int bar,
> - const char *name, int flags)
> + const char *name, int flags)
> {
> unsigned long offset = 0;
> unsigned long len = pci_resource_len(pdev, bar);
> @@ -208,7 +211,7 @@ static struct pcim_addr_devres
> *pcim_addr_devres_alloc(struct pci_dev *pdev)
> struct pcim_addr_devres *res;
>
> res = devres_alloc_node(pcim_addr_resource_release,
> sizeof(*res),
> - GFP_KERNEL, dev_to_node(&pdev->dev));
> + GFP_KERNEL, dev_to_node(&pdev->dev));
> if (res)
> pcim_addr_devres_clear(res);
> return res;
> @@ -223,7 +226,8 @@ static inline void pcim_addr_devres_free(struct
> pcim_addr_devres *res)
> /*
> * Used by devres to identify a pcim_addr_devres.
> */
> -static int pcim_addr_resources_match(struct device *dev, void
> *a_raw, void *b_raw)
> +static int pcim_addr_resources_match(struct device *dev,
> + void *a_raw, void *b_raw)
> {
> struct pcim_addr_devres *a, *b;
>
> @@ -402,7 +406,6 @@ int pcim_set_mwi(struct pci_dev *pdev)
> }
> EXPORT_SYMBOL(pcim_set_mwi);
>
> -
> static inline bool mask_contains_bar(int mask, int bar)
> {
> return mask & BIT(bar);
> @@ -438,8 +441,8 @@ static struct pcim_intx_devres
> *get_or_create_intx_devres(struct device *dev)
> *
> * Returns: 0 on success, -ENOMEM on error.
> *
> - * Enables/disables PCI INTx for device @pdev.
> - * Restores the original state on driver detach.
> + * Enable/disable PCI INTx for device @pdev.
> + * Restore the original state on driver detach.
> */
> int pcim_intx(struct pci_dev *pdev, int enable)
> {
> @@ -492,7 +495,7 @@ int pcim_enable_device(struct pci_dev *pdev)
>
> /*
> * We prefer removing the action in case of an error over
> - * devm_add_action_or_reset() because the later could
> theoretically be
> + * devm_add_action_or_reset() because the latter could
> theoretically be
> * disturbed by users having pinned the device too soon.
> */
> ret = pci_enable_device(pdev);
> @@ -618,7 +621,7 @@ static void
> pcim_remove_mapping_from_legacy_table(struct pci_dev *pdev,
> * The same as pcim_remove_mapping_from_legacy_table(), but
> identifies the
> * mapping by its BAR index.
> */
> -static void pcim_remove_bar_from_legacy_table(struct pci_dev *pdev,
> short bar)
> +static void pcim_remove_bar_from_legacy_table(struct pci_dev *pdev,
> int bar)
> {
> void __iomem **legacy_iomap_table;
>
> @@ -783,7 +786,7 @@ static void pcim_iounmap_region(struct pci_dev
> *pdev, int bar)
> int pcim_iomap_regions(struct pci_dev *pdev, int mask, const char
> *name)
> {
> int ret;
> - short bar;
> + int bar;
> void __iomem *mapping;
>
> for (bar = 0; bar < DEVICE_COUNT_RESOURCE; bar++) {
> @@ -813,7 +816,7 @@ int pcim_iomap_regions(struct pci_dev *pdev, int
> mask, const char *name)
> EXPORT_SYMBOL(pcim_iomap_regions);
>
> static int _pcim_request_region(struct pci_dev *pdev, int bar, const
> char *name,
> - int request_flags)
> + int request_flags)
> {
> int ret;
> struct pcim_addr_devres *res;
> @@ -903,7 +906,7 @@ void pcim_release_region(struct pci_dev *pdev,
> int bar)
> */
> static void pcim_release_all_regions(struct pci_dev *pdev)
> {
> - short bar;
> + int bar;
>
> for (bar = 0; bar < PCI_STD_NUM_BARS; bar++)
> pcim_release_region(pdev, bar);
> @@ -923,7 +926,7 @@ static void pcim_release_all_regions(struct
> pci_dev *pdev)
> static int pcim_request_all_regions(struct pci_dev *pdev, const char
> *name)
> {
> int ret;
> - short bar;
> + int bar;
>
> for (bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
> ret = pcim_request_region(pdev, bar, name);
> @@ -960,7 +963,7 @@ static int pcim_request_all_regions(struct
> pci_dev *pdev, const char *name)
> int pcim_iomap_regions_request_all(struct pci_dev *pdev, int mask,
> const char *name)
> {
> - short bar;
> + int bar;
> int ret;
> void __iomem **legacy_iomap_table;
>
> @@ -1004,14 +1007,14 @@
> EXPORT_SYMBOL(pcim_iomap_regions_request_all);
> */
> void pcim_iounmap_regions(struct pci_dev *pdev, int mask)
> {
> - short bar;
> + int i;
>
> - for (bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
> - if (!mask_contains_bar(mask, bar))
> + for (i = 0; i < PCI_STD_NUM_BARS; i++) {
> + if (!mask_contains_bar(mask, i))
> continue;
>
> - pcim_iounmap_region(pdev, bar);
> - pcim_remove_bar_from_legacy_table(pdev, bar);
> + pcim_iounmap_region(pdev, i);
> + pcim_remove_bar_from_legacy_table(pdev, i);
> }
> }
> EXPORT_SYMBOL(pcim_iounmap_regions);
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 1b4832a60047..807f8be043cd 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4073,6 +4073,11 @@ EXPORT_SYMBOL(pci_release_regions);
> *
> * Returns 0 on success, or %EBUSY on error. A warning
> * message is also printed on failure.
> + *
> + * NOTE:
> + * This is a "hybrid" function: It's normally unmanaged, but becomes
> managed
> + * when pcim_enable_device() has been called in advance. This hybrid
> feature is
> + * DEPRECATED! If you want managed cleanup, use the pcim_* functions
> instead.
> */
> int pci_request_regions(struct pci_dev *pdev, const char *res_name)
> {
> @@ -4437,17 +4442,13 @@ void pci_disable_parity(struct pci_dev *dev)
> * NOTE:
> * This is a "hybrid" function: It's normally unmanaged, but becomes
> managed
> * when pcim_enable_device() has been called in advance. This hybrid
> feature is
> - * DEPRECATED!
> + * DEPRECATED! If you want managed cleanup, use pcim_intx() instead.
> */
> void pci_intx(struct pci_dev *pdev, int enable)
> {
> u16 pci_command, new;
>
> - /*
> - * This is done for backwards compatibility, because the old
> PCI devres
> - * API had a mode in which this function became managed if
> the dev had
> - * been enabled with pcim_enable_device() instead of
> pci_enable_device().
> - */
> + /* Preserve the "hybrid" behavior for backwards compatibility
> */
> if (pci_is_managed(pdev)) {
> WARN_ON_ONCE(pcim_intx(pdev, enable) != 0);
> return;
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index e51e6fa79fcc..e6d299b93c21 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -813,7 +813,8 @@ static inline pci_power_t
> mid_pci_get_power_state(struct pci_dev *pdev)
> int pcim_intx(struct pci_dev *dev, int enable);
>
> int pcim_request_region(struct pci_dev *pdev, int bar, const char
> *name);
> -int pcim_request_region_exclusive(struct pci_dev *pdev, int bar,
> const char *name);
> +int pcim_request_region_exclusive(struct pci_dev *pdev, int bar,
> + const char *name);
> void pcim_release_region(struct pci_dev *pdev, int bar);
>
> /*
>
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