| Message ID | 60bc710b990ed1d45741888df7e97cf25d150e61.1713347222.git.oleksii.kurochko@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Enable build of full Xen for RISC-V | expand |
On 17.04.2024 12:04, Oleksii Kurochko wrote: > Return type was left 'int' because of the following compilation error: > > ./include/xen/kernel.h:18:21: error: comparison of distinct pointer types lacks a cast [-Werror] > 18 | (void) (&_x == &_y); \ > | ^~ > common/page_alloc.c:1843:34: note: in expansion of macro 'min' > 1843 | unsigned int inc_order = min(MAX_ORDER, flsl(e - s) - 1); Apart from this I'm okay with this patch, assuming Andrew's won't change in any conflicting way. As to the above - no, I don't see us having ffs() / ffsl() returning unsigned int, fls() / flsl() returning plain int. Even more so that, given the LHS variable's type, an unsigned quantity is really meant in the quoted code. Jan
On Thu, 2024-04-25 at 17:44 +0200, Jan Beulich wrote: > On 17.04.2024 12:04, Oleksii Kurochko wrote: > > Return type was left 'int' because of the following compilation > > error: > > > > ./include/xen/kernel.h:18:21: error: comparison of distinct pointer > > types lacks a cast [-Werror] > > 18 | (void) (&_x == &_y); \ > > | ^~ > > common/page_alloc.c:1843:34: note: in expansion of macro 'min' > > 1843 | unsigned int inc_order = min(MAX_ORDER, flsl(e > > - s) - 1); > > Apart from this I'm okay with this patch, assuming Andrew's won't > change in > any conflicting way. As to the above - no, I don't see us having > ffs() / ffsl() > returning unsigned int, fls() / flsl() returning plain int. Even more > so that, > given the LHS variable's type, an unsigned quantity is really meant > in the > quoted code. If I understand you correctly, it's acceptable for fls() / flsl() to return 'int'. Therefore, I can update the commit message by removing the part mentioning the compilation error, as it's expected for fls() / flsl() to return 'int'. Is my understanding correct? ~ Oleksii
On 26.04.2024 10:21, Oleksii wrote: > On Thu, 2024-04-25 at 17:44 +0200, Jan Beulich wrote: >> On 17.04.2024 12:04, Oleksii Kurochko wrote: >>> Return type was left 'int' because of the following compilation >>> error: >>> >>> ./include/xen/kernel.h:18:21: error: comparison of distinct pointer >>> types lacks a cast [-Werror] >>> 18 | (void) (&_x == &_y); \ >>> | ^~ >>> common/page_alloc.c:1843:34: note: in expansion of macro 'min' >>> 1843 | unsigned int inc_order = min(MAX_ORDER, flsl(e >>> - s) - 1); >> >> Apart from this I'm okay with this patch, assuming Andrew's won't >> change in >> any conflicting way. As to the above - no, I don't see us having >> ffs() / ffsl() >> returning unsigned int, fls() / flsl() returning plain int. Even more >> so that, >> given the LHS variable's type, an unsigned quantity is really meant >> in the >> quoted code. > If I understand you correctly, it's acceptable for fls() / flsl() to > return 'int'. Therefore, I can update the commit message by removing > the part mentioning the compilation error, as it's expected for fls() / > flsl() to return 'int'. Is my understanding correct? No. I firmly object to ffs() and fls() being different in their return types. I'm sorry, I realize now that my earlier wording was ambiguous (at least missing "but" after the comma). Jan
On Fri, 2024-04-26 at 12:51 +0200, Jan Beulich wrote: > On 26.04.2024 10:21, Oleksii wrote: > > On Thu, 2024-04-25 at 17:44 +0200, Jan Beulich wrote: > > > On 17.04.2024 12:04, Oleksii Kurochko wrote: > > > > Return type was left 'int' because of the following compilation > > > > error: > > > > > > > > ./include/xen/kernel.h:18:21: error: comparison of distinct > > > > pointer > > > > types lacks a cast [-Werror] > > > > 18 | (void) (&_x == &_y); \ > > > > | ^~ > > > > common/page_alloc.c:1843:34: note: in expansion of macro > > > > 'min' > > > > 1843 | unsigned int inc_order = min(MAX_ORDER, > > > > flsl(e > > > > - s) - 1); > > > > > > Apart from this I'm okay with this patch, assuming Andrew's won't > > > change in > > > any conflicting way. As to the above - no, I don't see us having > > > ffs() / ffsl() > > > returning unsigned int, fls() / flsl() returning plain int. Even > > > more > > > so that, > > > given the LHS variable's type, an unsigned quantity is really > > > meant > > > in the > > > quoted code. > > If I understand you correctly, it's acceptable for fls() / flsl() > > to > > return 'int'. Therefore, I can update the commit message by > > removing > > the part mentioning the compilation error, as it's expected for > > fls() / > > flsl() to return 'int'. Is my understanding correct? > > No. I firmly object to ffs() and fls() being different in their > return > types. I'm sorry, I realize now that my earlier wording was ambiguous > (at least missing "but" after the comma). Thanks for clarifying. I can change return type of fls() / flsl() to 'unsingned int' to be the same as return type of ffs() / ffsl(), but then it will be needed to add a cast in two places: --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -1842,7 +1842,7 @@ static void _init_heap_pages(const struct page_info *pg, * Note that the value of ffsl() and flsl() starts from 1 so we need * to decrement it by 1. */ - unsigned int inc_order = min(MAX_ORDER, flsl(e - s) - 1); + unsigned int inc_order = min((unsigned int)MAX_ORDER, flsl(e - s) - 1); if ( s ) inc_order = min(inc_order, ffsl(s) - 1U); @@ -2266,7 +2266,7 @@ void __init xenheap_max_mfn(unsigned long mfn) ASSERT(!first_node_initialised); ASSERT(!xenheap_bits); BUILD_BUG_ON((PADDR_BITS - PAGE_SHIFT) >= BITS_PER_LONG); - xenheap_bits = min(flsl(mfn + 1) - 1 + PAGE_SHIFT, PADDR_BITS); + xenheap_bits = min(flsl(mfn + 1) - 1 + PAGE_SHIFT, (unsigned int)PADDR_BITS); printk(XENLOG_INFO "Xen heap: %u bits\n", xenheap_bits); } If it looks okay, then I'll do that in the next patch version. ~ Oleksii
On 26.04.2024 14:09, Oleksii wrote: > On Fri, 2024-04-26 at 12:51 +0200, Jan Beulich wrote: >> On 26.04.2024 10:21, Oleksii wrote: >>> On Thu, 2024-04-25 at 17:44 +0200, Jan Beulich wrote: >>>> On 17.04.2024 12:04, Oleksii Kurochko wrote: >>>>> Return type was left 'int' because of the following compilation >>>>> error: >>>>> >>>>> ./include/xen/kernel.h:18:21: error: comparison of distinct >>>>> pointer >>>>> types lacks a cast [-Werror] >>>>> 18 | (void) (&_x == &_y); \ >>>>> | ^~ >>>>> common/page_alloc.c:1843:34: note: in expansion of macro >>>>> 'min' >>>>> 1843 | unsigned int inc_order = min(MAX_ORDER, >>>>> flsl(e >>>>> - s) - 1); >>>> >>>> Apart from this I'm okay with this patch, assuming Andrew's won't >>>> change in >>>> any conflicting way. As to the above - no, I don't see us having >>>> ffs() / ffsl() >>>> returning unsigned int, fls() / flsl() returning plain int. Even >>>> more >>>> so that, >>>> given the LHS variable's type, an unsigned quantity is really >>>> meant >>>> in the >>>> quoted code. >>> If I understand you correctly, it's acceptable for fls() / flsl() >>> to >>> return 'int'. Therefore, I can update the commit message by >>> removing >>> the part mentioning the compilation error, as it's expected for >>> fls() / >>> flsl() to return 'int'. Is my understanding correct? >> >> No. I firmly object to ffs() and fls() being different in their >> return >> types. I'm sorry, I realize now that my earlier wording was ambiguous >> (at least missing "but" after the comma). > Thanks for clarifying. > > I can change return type of fls() / flsl() to 'unsingned int' to be the > same as return type of ffs() / ffsl(), but then it will be needed to > add a cast in two places: Except that no, it doesn't really need casts there. > --- a/xen/common/page_alloc.c > +++ b/xen/common/page_alloc.c > @@ -1842,7 +1842,7 @@ static void _init_heap_pages(const struct > page_info *pg, > * Note that the value of ffsl() and flsl() starts from 1 > so we need > * to decrement it by 1. > */ > - unsigned int inc_order = min(MAX_ORDER, flsl(e - s) - 1); > + unsigned int inc_order = min((unsigned int)MAX_ORDER, > flsl(e - s) - 1); The preferred course of action would want to be to simply make MAX_ORDER expand to an unsigned constant. Depending on the amount of fallout, an alternative would be to use _AC(MAX_ORDER, U) here. Yet another alternative would be to use MAX_ORDER + 0U here, as iirc we do in a few other places, for similar purposes. Avoiding a cast here is not only shorter, but - see statements elsewhere - generally preferable. Jan
diff --git a/xen/arch/arm/include/asm/arm32/bitops.h b/xen/arch/arm/include/asm/arm32/bitops.h index d0309d47c1..5552d4e945 100644 --- a/xen/arch/arm/include/asm/arm32/bitops.h +++ b/xen/arch/arm/include/asm/arm32/bitops.h @@ -1,7 +1,7 @@ #ifndef _ARM_ARM32_BITOPS_H #define _ARM_ARM32_BITOPS_H -#define flsl fls +#define arch_flsl fls /* * Little endian assembly bitops. nr = 0 -> byte 0 bit 0. diff --git a/xen/arch/arm/include/asm/arm64/bitops.h b/xen/arch/arm/include/asm/arm64/bitops.h index 0efde29068..5f5d97faa0 100644 --- a/xen/arch/arm/include/asm/arm64/bitops.h +++ b/xen/arch/arm/include/asm/arm64/bitops.h @@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long __ffs(unsigned long word) */ #define ffz(x) __ffs(~(x)) -static inline int flsl(unsigned long x) +static inline int arch_flsl(unsigned long x) { uint64_t ret; - if (__builtin_constant_p(x)) - return generic_flsl(x); - asm("clz\t%0, %1" : "=r" (ret) : "r" (x)); return BITS_PER_LONG - ret; } +#define arch_flsl arch_flsl /* Based on linux/include/asm-generic/bitops/find.h */ diff --git a/xen/arch/arm/include/asm/bitops.h b/xen/arch/arm/include/asm/bitops.h index 8e16335e76..860d6d4689 100644 --- a/xen/arch/arm/include/asm/bitops.h +++ b/xen/arch/arm/include/asm/bitops.h @@ -78,17 +78,14 @@ bool clear_mask16_timeout(uint16_t mask, volatile void *p, * the clz instruction for much better code efficiency. */ -static inline int fls(unsigned int x) +static inline int arch_fls(unsigned int x) { int ret; - if (__builtin_constant_p(x)) - return generic_fls(x); - asm("clz\t%"__OP32"0, %"__OP32"1" : "=r" (ret) : "r" (x)); return 32 - ret; } - +#define arch_fls arch_fls #define arch_ffs(x) ({ unsigned int __t = (x); fls(ISOLATE_LSB(__t)); }) #define arch_ffsl(x) ({ unsigned long __t = (x); flsl(ISOLATE_LSB(__t)); }) diff --git a/xen/arch/ppc/include/asm/bitops.h b/xen/arch/ppc/include/asm/bitops.h index e2b6473c8c..ca308fd62b 100644 --- a/xen/arch/ppc/include/asm/bitops.h +++ b/xen/arch/ppc/include/asm/bitops.h @@ -119,9 +119,6 @@ static inline int test_and_set_bit(unsigned int nr, volatile void *addr) (volatile unsigned int *)addr + BITOP_WORD(nr)) != 0; } -#define flsl(x) generic_flsl(x) -#define fls(x) generic_fls(x) - /* Based on linux/include/asm-generic/bitops/ffz.h */ /* * ffz - find first zero in word. diff --git a/xen/arch/x86/include/asm/bitops.h b/xen/arch/x86/include/asm/bitops.h index 2b2d9219ef..5d5b9445c5 100644 --- a/xen/arch/x86/include/asm/bitops.h +++ b/xen/arch/x86/include/asm/bitops.h @@ -430,7 +430,7 @@ static always_inline unsigned int arch_ffsl(unsigned long x) * * This is defined the same way as ffs. */ -static inline int flsl(unsigned long x) +static always_inline int arch_flsl(unsigned long x) { long r; @@ -440,8 +440,9 @@ static inline int flsl(unsigned long x) "1:" : "=r" (r) : "rm" (x)); return (int)r+1; } +#define arch_flsl arch_flsl -static inline int fls(unsigned int x) +static always_inline int arch_fls(unsigned int x) { int r; @@ -451,6 +452,7 @@ static inline int fls(unsigned int x) "1:" : "=r" (r) : "rm" (x)); return r + 1; } +#define arch_fls arch_fls /** * hweightN - returns the hamming weight of a N-bit word diff --git a/xen/common/bitops.c b/xen/common/bitops.c index a8c32f6767..95bc47176b 100644 --- a/xen/common/bitops.c +++ b/xen/common/bitops.c @@ -62,9 +62,31 @@ static void test_ffs(void) CHECK(ffs64, (uint64_t)0x8000000000000000, 64); } +static void test_fls(void) +{ + /* unsigned int ffs(unsigned int) */ + CHECK(fls, 1, 1); + CHECK(fls, 3, 2); + CHECK(fls, 3U << 30, 32); + + /* unsigned int flsl(unsigned long) */ + CHECK(flsl, 1, 1); + CHECK(flsl, 1UL << (BITS_PER_LONG - 1), BITS_PER_LONG); +#if BITS_PER_LONG > 32 + CHECK(flsl, 3UL << 32, 34); +#endif + + /* unsigned int fls64(uint64_t) */ + CHECK(fls64, 1, 1); + CHECK(fls64, 0x00000000C0000000ULL, 32); + CHECK(fls64, 0x0000000180000000ULL, 33); + CHECK(fls64, 0xC000000000000000ULL, 64); +} + static int __init cf_check test_bitops(void) { test_ffs(); + test_fls(); return 0; } diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h index a41ec44064..a7edee4a95 100644 --- a/xen/include/xen/bitops.h +++ b/xen/include/xen/bitops.h @@ -196,6 +196,30 @@ static always_inline bool test_bit(int nr, const volatile void *addr) test_bit(nr, addr); \ }) +static always_inline __pure int fls(unsigned int x) +{ + if ( __builtin_constant_p(x) ) + return generic_fls(x); + +#ifndef arch_fls +#define arch_fls generic_fls +#endif + + return arch_fls(x); +} + +static always_inline __pure int flsl(unsigned long x) +{ + if ( __builtin_constant_p(x) ) + return generic_flsl(x); + +#ifndef arch_flsl +#define arch_flsl generic_flsl +#endif + + return arch_flsl(x); +} + /* * Find First Set bit. Bits are labelled from 1. */
Return type was left 'int' because of the following compilation error: ./include/xen/kernel.h:18:21: error: comparison of distinct pointer types lacks a cast [-Werror] 18 | (void) (&_x == &_y); \ | ^~ common/page_alloc.c:1843:34: note: in expansion of macro 'min' 1843 | unsigned int inc_order = min(MAX_ORDER, flsl(e - s) - 1); generic_fls{l} was used instead of __builtin_clz{l}(x) as if x is 0, the result in undefined. Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com> --- The patch is almost independent from Andrew's patch series ( https://lore.kernel.org/xen-devel/20240313172716.2325427-1-andrew.cooper3@citrix.com/T/#t) except test_fls() function which IMO can be merged as a separate patch after Andrew's patch will be fully ready. --- Changes in V8: - do proper rebase: back definition of fls{l} to the current patch. - drop the changes which removed ffz() in PPC. it should be done not in this patch. - add a message after Signed-off. --- Changes in V7: - Code style fixes --- Changes in V6: - new patch for the patch series. --- xen/arch/arm/include/asm/arm32/bitops.h | 2 +- xen/arch/arm/include/asm/arm64/bitops.h | 6 ++---- xen/arch/arm/include/asm/bitops.h | 7 ++----- xen/arch/ppc/include/asm/bitops.h | 3 --- xen/arch/x86/include/asm/bitops.h | 6 ++++-- xen/common/bitops.c | 22 ++++++++++++++++++++++ xen/include/xen/bitops.h | 24 ++++++++++++++++++++++++ 7 files changed, 55 insertions(+), 15 deletions(-)