| Message ID | 20241210-packing-pack-fields-and-ice-implementation-v10-0-ee56a47479ac@intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | lib: packing: introduce and use (un)pack_fields | expand |
On Tue, Dec 10, 2024 at 12:27:09PM -0800, Jacob Keller wrote: > This series improves the packing library with a new API for packing or > unpacking a large number of fields at once with minimal code footprint. The > API is then used to replace bespoke packing logic in the ice driver, > preparing it to handle unpacking in the future. Finally, the ice driver has > a few other cleanups related to the packing logic. > > The pack_fields and unpack_fields functions have the following improvements > over the existing pack() and unpack() API: > > 1. Packing or unpacking a large number of fields takes significantly less > code. This significantly reduces the .text size for an increase in the > .data size which is much smaller. > > 2. The unpacked data can be stored in sizes smaller than u64 variables. > This reduces the storage requirement both for runtime data structures, > and for the rodata defining the fields. This scales with the number of > fields used. > > 3. Most of the error checking is done at compile time, rather than > runtime, via CHECK_PACKED_FIELD macros. > > The actual packing and unpacking code still uses the u64 size > variables. However, these are converted to the appropriate field sizes when > storing or reading the data from the buffer. > > This version now uses significantly improved macro checks, thanks to the > work of Vladimir. We now only need 300 lines of macro for the generated > checks. In addition, each new check only requires 4 lines of code for its > macro implementation and 1 extra line in the CHECK_PACKED_FIELDS macro. > This is significantly better than previous versions which required ~2700 > lines. > > The CHECK_PACKED_FIELDS macro uses __builtin_choose_expr to select the > appropriately sized CHECK_PACKED_FIELDS_N macro. This enables directly > adding CHECK_PACKED_FIELDS calls into the pack_fields and unpack_fields > macros. Drivers no longer need to call the CHECK_PACKED_FIELDS_N macros > directly, and we do not need to modify Kbuild or introduce multiple CONFIG > options. > > The code for the CHECK_PACKED_FIELDS_(0..50) and CHECK_PACKED_FIELDS itself > can be generated from the C program in scripts/gen_packed_field_checks.c. > This little C program may be used in the future to update the checks to > more sizes if a driver with more than 50 fields appears in the future. > The total amount of required code is now much smaller, and we don't > anticipate needing to increase the size very often. Thus, it makes sense to > simply commit the result directly instead of attempting to modify Kbuild to > automatically generate it. > > This version uses the 5-argument format of pack_fields and unpack_fields, > with the size of the packed buffer passed as one of the arguments. We do > enforce that the compiler can tell its a constant using > __builtin_constant_p(), ensuring that the size checks are handled at > compile time. We could reduce these to 4 arguments and require that the > passed in pbuf be of a type which has the appropriate size. I opted against > that because it makes the API less flexible and a bit less natural to use > in existing code. > > Signed-off-by: Jacob Keller <jacob.e.keller@intel.com> > --- Any reason why you aren't carrying over my review and test tags from one version to another? Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Hello: This series was applied to netdev/net-next.git (main) by Jakub Kicinski <kuba@kernel.org>: On Tue, 10 Dec 2024 12:27:09 -0800 you wrote: > This series improves the packing library with a new API for packing or > unpacking a large number of fields at once with minimal code footprint. The > API is then used to replace bespoke packing logic in the ice driver, > preparing it to handle unpacking in the future. Finally, the ice driver has > a few other cleanups related to the packing logic. > > The pack_fields and unpack_fields functions have the following improvements > over the existing pack() and unpack() API: > > [...] Here is the summary with links: - [net-next,v10,01/10] lib: packing: create __pack() and __unpack() variants without error checking https://git.kernel.org/netdev/net-next/c/c4117091d029 - [net-next,v10,02/10] lib: packing: demote truncation error in pack() to a warning in __pack() https://git.kernel.org/netdev/net-next/c/48c2752785ad - [net-next,v10,03/10] lib: packing: add pack_fields() and unpack_fields() (no matching commit) - [net-next,v10,04/10] lib: packing: document recently added APIs https://git.kernel.org/netdev/net-next/c/a9ad2a8dfb43 - [net-next,v10,05/10] ice: remove int_q_state from ice_tlan_ctx (no matching commit) - [net-next,v10,06/10] ice: use structures to keep track of queue context size (no matching commit) - [net-next,v10,07/10] ice: use <linux/packing.h> for Tx and Rx queue context data (no matching commit) - [net-next,v10,08/10] ice: reduce size of queue context fields https://git.kernel.org/netdev/net-next/c/f72588a4267b - [net-next,v10,09/10] ice: move prefetch enable to ice_setup_rx_ctx https://git.kernel.org/netdev/net-next/c/ac001acc4d35 - [net-next,v10,10/10] ice: cleanup Rx queue context programming functions https://git.kernel.org/netdev/net-next/c/39be64c34ca3 You are awesome, thank you!
This series improves the packing library with a new API for packing or unpacking a large number of fields at once with minimal code footprint. The API is then used to replace bespoke packing logic in the ice driver, preparing it to handle unpacking in the future. Finally, the ice driver has a few other cleanups related to the packing logic. The pack_fields and unpack_fields functions have the following improvements over the existing pack() and unpack() API: 1. Packing or unpacking a large number of fields takes significantly less code. This significantly reduces the .text size for an increase in the .data size which is much smaller. 2. The unpacked data can be stored in sizes smaller than u64 variables. This reduces the storage requirement both for runtime data structures, and for the rodata defining the fields. This scales with the number of fields used. 3. Most of the error checking is done at compile time, rather than runtime, via CHECK_PACKED_FIELD macros. The actual packing and unpacking code still uses the u64 size variables. However, these are converted to the appropriate field sizes when storing or reading the data from the buffer. This version now uses significantly improved macro checks, thanks to the work of Vladimir. We now only need 300 lines of macro for the generated checks. In addition, each new check only requires 4 lines of code for its macro implementation and 1 extra line in the CHECK_PACKED_FIELDS macro. This is significantly better than previous versions which required ~2700 lines. The CHECK_PACKED_FIELDS macro uses __builtin_choose_expr to select the appropriately sized CHECK_PACKED_FIELDS_N macro. This enables directly adding CHECK_PACKED_FIELDS calls into the pack_fields and unpack_fields macros. Drivers no longer need to call the CHECK_PACKED_FIELDS_N macros directly, and we do not need to modify Kbuild or introduce multiple CONFIG options. The code for the CHECK_PACKED_FIELDS_(0..50) and CHECK_PACKED_FIELDS itself can be generated from the C program in scripts/gen_packed_field_checks.c. This little C program may be used in the future to update the checks to more sizes if a driver with more than 50 fields appears in the future. The total amount of required code is now much smaller, and we don't anticipate needing to increase the size very often. Thus, it makes sense to simply commit the result directly instead of attempting to modify Kbuild to automatically generate it. This version uses the 5-argument format of pack_fields and unpack_fields, with the size of the packed buffer passed as one of the arguments. We do enforce that the compiler can tell its a constant using __builtin_constant_p(), ensuring that the size checks are handled at compile time. We could reduce these to 4 arguments and require that the passed in pbuf be of a type which has the appropriate size. I opted against that because it makes the API less flexible and a bit less natural to use in existing code. Signed-off-by: Jacob Keller <jacob.e.keller@intel.com> --- Changes in v10: - Use '_u8' and '_u16' suffix instead of '_s' and '_m', for packed_field_* and (un)pack_fields_*. - Add gen_packed_field_checks to scripts/.gitignore - Add a note to the kdoc for the pack_fields_* and unpack_fields_* functions about preferring use of the macro. - Link to v9: https://lore.kernel.org/r/20241204-packing-pack-fields-and-ice-implementation-v9-0-81c8f2bd7323@intel.com Changes in v9: - Use BUILD_BUG_ON_MSG to provide more useful and detailed error messages, including the field array name, associated field index values, and the actual rule being violated. This improves the usability of the resulting error messages, especially for users unfamiliar with the API requirements. - New implementation of CHECK_PACKED_FIELD and CHECK_PACKED_FIELD_OVERLAP, taking the reference of the total array field directly. This allows tail-calling the CHECK_PACKED_FIELD_OVERLAP from within CHECK_PACKED_FIELD, significantly reducing the number of lines required to implement all the macros. - Drop the ARRAY_SIZE checks from the CHECK_PACKED_FIELDS_* macros. These were only necessary when users called the macros directly. Now that we always use __builtin_choose_expr to determine which one to call, this is a waste of the CPU cycles. - Implement each CHECK_PACKED_FIELD_N recursively, by calling the previous CHECK_PACKED_FIELD_* macro. This means each additional macro now only needs 4 lines of code, instead of scaling linearly with the size of N. This is possible now that we no longer directly check the ARRAY_SIZE in each macro. - Use do {} while(0) for implementing the multiline checks in each CHECK_PACKED_FIELD_* macro, instead of statement expressions. This helps with GCC giving up on processing due to the multiple layers of statement expressions when evaluating the CHECK_PACKED_FIELD_* macros. - Link to v8: https://lore.kernel.org/r/20241203-packing-pack-fields-and-ice-implementation-v8-0-2ed68edfe583@intel.com Changes in v8: - Add my missing SOB on one of the patches - Remove include/linux/packing_types.h and put the generated code directly into include/linux/packing.h - Split documentation to its own patch, and use the proposed documentation from Vladimir - Link to v7: https://lore.kernel.org/r/20241202-packing-pack-fields-and-ice-implementation-v7-0-ed22e38e6c65@intel.com Changes in v7: - Dropped the RFC tag for submission to net-next - Link to v6: https://lore.kernel.org/r/20241118-packing-pack-fields-and-ice-implementation-v6-0-6af8b658a6c3@intel.com Changes in v6: - Revert to macro checks similar to v2. - Add a __builtin_choose_expr() based macro to automatically select the appropriate size macro. - Keep the pbuflen check separate from the main loop check, similar to v5. - Link to v5: https://lore.kernel.org/r/20241111-packing-pack-fields-and-ice-implementation-v5-0-80c07349e6b7@intel.com Changes in v5: - Fix printf format specifier for the sym->st_size - Link to v4: https://lore.kernel.org/r/20241108-packing-pack-fields-and-ice-implementation-v4-0-81a9f42c30e5@intel.com Changes in v4: - Move the buffer size checks to (un)pack_fields() macros. - Enforce use of a sized type of the packed buffer, removing the now unnecessary pbuflen argument of (un)pack_fields(). - Drop exporting the buffer size to modpost. - Simplify modpost implementation to directly check each symbol in the handle_packed_field_symbol() function. This removes the need for a hash, and is ultimately much simpler now that modpost doesn't need the size of the target buffer. - Fix the width check to correctly calculate the width and compare it properly. - Refactor modpost messages to consistently report the module name first, the symbol name second, and the field number 3rd. - Correctly implement overlap checks in the modpost, rather than only checking field ordering. - Link to v3: https://lore.kernel.org/r/20241107-packing-pack-fields-and-ice-implementation-v3-0-27c566ac2436@intel.com Changes in v3: - Replace macro-based C pre-processor checks with checks implemented in modpost. - Move structure definitions into <linux/packing_types.h> to enable reuse within modpost. - Add DECLARE_PACKED_FIELDS_S and DECLARE_PACKED_FIELDS_M to enable automatically generating the buffer size constants and the section attributes. - Add additional unit tests for the pack_fields and unpack_fields APIs. - Update documentation with an explanation of the new API as well as some example code. - Link to v2: https://lore.kernel.org/r/20241025-packing-pack-fields-and-ice-implementation-v2-0-734776c88e40@intel.com Changes in v2: - Add my missing sign-off to the first patch - Update the descriptions for a few patches - Only generate CHECK_PACKED_FIELDS_N when another module selects it - Add a new patch introducing wrapper structures for the packed Tx and Rx queue context, suggested by Vladimir. - Drop the now unnecessary macros in ice, thanks to the new types - Link to v1: https://lore.kernel.org/r/20241011-packing-pack-fields-and-ice-implementation-v1-0-d9b1f7500740@intel.com --- Jacob Keller (7): lib: packing: document recently added APIs ice: remove int_q_state from ice_tlan_ctx ice: use structures to keep track of queue context size ice: use <linux/packing.h> for Tx and Rx queue context data ice: reduce size of queue context fields ice: move prefetch enable to ice_setup_rx_ctx ice: cleanup Rx queue context programming functions Vladimir Oltean (3): lib: packing: create __pack() and __unpack() variants without error checking lib: packing: demote truncation error in pack() to a warning in __pack() lib: packing: add pack_fields() and unpack_fields() Makefile | 4 + drivers/net/ethernet/intel/ice/ice_adminq_cmd.h | 11 +- drivers/net/ethernet/intel/ice/ice_common.h | 5 +- drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h | 49 +-- include/linux/packing.h | 425 ++++++++++++++++++++++++ drivers/net/dsa/sja1105/sja1105_static_config.c | 8 +- drivers/net/ethernet/intel/ice/ice_base.c | 6 +- drivers/net/ethernet/intel/ice/ice_common.c | 293 ++++------------ lib/packing.c | 293 ++++++++++++---- lib/packing_test.c | 61 ++++ scripts/gen_packed_field_checks.c | 37 +++ Documentation/core-api/packing.rst | 118 ++++++- MAINTAINERS | 1 + drivers/net/ethernet/intel/Kconfig | 1 + scripts/.gitignore | 1 + scripts/Makefile | 2 +- 16 files changed, 955 insertions(+), 360 deletions(-) --- base-commit: a0e1fc921cb0651cd11469bf5378ec342bf7094d change-id: 20241004-packing-pack-fields-and-ice-implementation-b17c7ce8e373 Best regards,