Re: [PATCH v9 00/13] Make PCI's devres API more consistent

Bjorn Helgaas
2024-06-13T21:57:45Z

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 - Remove the comment advising to call (the outdated) pcim_intx() in pci.c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.

Planned for v6.11.

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);

/*