kernel/linux.git/include/linux/math64.h, branch v6.12.80

ice: add and use roundup_u64 instead of open coding equivalent

2024-06-11T02:52:44+00:00

In ice_ptp_cfg_clkout(), the ice driver needs to calculate the nearest next second of a current time value specified in nanoseconds. It implements this using div64_u64, because the time value is a u64. It could use div_u64 since NSEC_PER_SEC is smaller than 32-bits. Ideally this would be implemented directly with roundup(), but that can't work on all platforms due to a division which requires using the specific macros and functions due to platform restrictions, and to ensure that the most appropriate and fast instructions are used. The kernel doesn't currently provide any 64-bit equivalents for doing roundup. Attempting to use roundup() on a 32-bit platform will result in a link failure due to not having a direct 64-bit division. The closest equivalent for this is DIV64_U64_ROUND_UP, which does a division always rounding up. However, this only computes the division, and forces use of the div64_u64 in cases where the divisor is a 32bit value and could make use of div_u64. Introduce DIV_U64_ROUND_UP based on div_u64, and then use it to implement roundup_u64 which takes a u64 input value and a u32 rounding value. The name roundup_u64 matches the naming scheme of div_u64, and future patches could implement roundup64_u64 if they need to round by a multiple that is greater than 32-bits. Replace the logic in ice_ptp.c which does this equivalent with the newly added roundup_u64. Tested-by: Pucha Himasekhar Reddy Signed-off-by: Jacob Keller Link: https://lore.kernel.org/r/20240607-next-2024-06-03-intel-next-batch-v3-2-d1470cee3347@intel.com Signed-off-by: Jakub Kicinski

vdso, math64: Provide mul_u64_u32_add_u64_shr()

2024-04-08T13:03:07+00:00

Provide mul_u64_u32_add_u64_shr() which is a calculation that will be used by timekeeping and VDSO. Place #include after #include to allow architecture-specific overrides, at least for the kernel. Signed-off-by: Adrian Hunter Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240325064023.2997-6-adrian.hunter@intel.com

math64: Tidy up mul_u64_u32_shr()

2024-04-08T13:03:06+00:00

Put together declaration and initialization of local variables. Suggested-by: Thomas Gleixner Signed-off-by: Adrian Hunter Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240325064023.2997-5-adrian.hunter@intel.com

math64: Always inline u128 version of mul_u64_u64_shr()

2023-06-05T19:11:06+00:00

In order to prevent the following complaint from happening, always inline the u128 variant of mul_u64_u64_shr() -- which is what x86_64 will use. vmlinux.o: warning: objtool: read_hv_sched_clock_tsc+0x5a: call to mul_u64_u64_shr.constprop.0() leaves .noinstr.text section It should compile into something like: asm("mul %[mul];" "shrd %rdx, %rax, %cl" : "+&a" (a) : "c" shift, [mul] "r" (mul) : "d"); Which is silly not to inline, but it happens. Signed-off-by: Peter Zijlstra (Intel) Tested-by: Michael Kelley # Hyper-V Link: https://lore.kernel.org/r/20230519102715.637420396@infradead.org

sched/clock/x86: Mark sched_clock() noinstr

2023-01-31T14:01:47+00:00

In order to use sched_clock() from noinstr code, mark it and all it's implenentations noinstr. The whole pvclock thing (used by KVM/Xen) is a bit of a pain, since it calls out to watchdogs, create a pvclock_clocksource_read_nowd() variant doesn't do that and can be noinstr. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20230126151323.702003578@infradead.org

math64: fix kernel-doc return value warnings

2022-11-21T21:30:54+00:00

Fix the following kernel-doc warnings by adding a description for return values of div_[us]64. math64.h:126: warning: No description found for return value of 'div_u64' math64.h:139: warning: No description found for return value of 'div_s64' Signed-off-by: Liam Beguin Link: https://lore.kernel.org/r/20221118182309.3824530-3-liambeguin@gmail.com Signed-off-by: Jonathan Corbet

math64: add kernel-doc for DIV64_U64_ROUND_UP

2022-11-21T21:30:54+00:00

Add kernel-doc for DIV64_U64_ROUND_UP so that it appears in the documentation. Signed-off-by: Liam Beguin Acked-by: Randy Dunlap Tested-by: Randy Dunlap Link: https://lore.kernel.org/r/20221118182309.3824530-2-liambeguin@gmail.com Signed-off-by: Jonathan Corbet

math64: favor kernel-doc from header files

2022-11-21T21:30:53+00:00

Fix the kernel-doc markings for div64 functions to point to the header file instead of the lib/ directory. This avoids having implementation specific comments in generic documentation. Furthermore, given that some kernel-doc comments are identical, drop them from lib/math64 and only keep there comments that add implementation details. Signed-off-by: Liam Beguin Acked-by: Randy Dunlap Tested-by: Randy Dunlap Link: https://lore.kernel.org/r/20221118182309.3824530-1-liambeguin@gmail.com Signed-off-by: Jonathan Corbet

math64: New DIV_U64_ROUND_CLOSEST helper

2022-02-25T09:27:57+00:00

Provide DIV_U64_ROUND_CLOSEST helper which uses div_u64 to perform division rounded to the closest integer using unsigned 64bit dividend and unsigned 32bit divisor. Reviewed-by: Marek Behún Signed-off-by: Pali Rohár Signed-off-by: Marek Behún Link: https://lore.kernel.org/r/20220219152818.4319-2-kabel@kernel.org Signed-off-by: Greg Kroah-Hartman

math64.h: Add mul_s64_u64_shr()

2021-06-17T17:09:27+00:00

This function is needed for KVM's nested virtualization. The nested TSC scaling implementation requires multiplying the signed TSC offset with the unsigned TSC multiplier. Signed-off-by: Ilias Stamatis Reviewed-by: Maxim Levitsky Message-Id: <20210526184418.28881-2-ilstam@amazon.com> Signed-off-by: Paolo Bonzini