On 09/11/2017 02:37 PM, Peter Maydell wrote: > On 11 September 2017 at 21:49, Philippe Mathieu-Daudé <f4...@amsat.org> wrote: >> this fixes building for ppc64 on ppc32 (changed in 5964fca8a12c): >> >> qemu/tcg/ppc/tcg-target.inc.c: In function 'tb_target_set_jmp_target': >> qemu/include/qemu/compiler.h:86:30: error: static assertion failed: "not >> expecting: sizeof(*(uint64_t *)jmp_addr) > ATOMIC_REG_SIZE" >> QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \ >> ^ >> qemu/tcg/ppc/tcg-target.inc.c:1377:9: note: in expansion of macro >> 'atomic_set' >> atomic_set((uint64_t *)jmp_addr, pair); >> ^ >> >> Suggested-by: Richard Henderson <r...@twiddle.net> >> Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org> >> --- >> This fixes Shippable builds, see: >> https://app.shippable.com/github/qemu/qemu/runs/434/10/console >> >> tcg/ppc/tcg-target.inc.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/tcg/ppc/tcg-target.inc.c b/tcg/ppc/tcg-target.inc.c >> index 21d764c102..0417901289 100644 >> --- a/tcg/ppc/tcg-target.inc.c >> +++ b/tcg/ppc/tcg-target.inc.c >> @@ -1374,7 +1374,7 @@ void tb_target_set_jmp_target(uintptr_t tc_ptr, >> uintptr_t jmp_addr, >> pair = (uint64_t)i2 << 32 | i1; >> #endif >> >> - atomic_set((uint64_t *)jmp_addr, pair); >> + atomic_set__nocheck((uint64_t *)jmp_addr, pair); >> flush_icache_range(jmp_addr, jmp_addr + 8); >> } else { >> intptr_t diff = addr - jmp_addr; > > Can you explain why this is the right thing? On the > face of it it looks correct to insist that we don't > try to do an atomic set of something that's bigger > than the host can actually handle...
It is the correct thing because ppc32 is handled earlier in the function; only ppc64 can reach here, therefore a 64-bit atomic_set is always available. However, I wrote the function intending to minimize the ifdefs so that we can be sure that it all compiles -- especially the ppc32 bits which I cannot test on gcc cfarm machines. I didn't think about the fact that ppc32 could not compile the _Static_assert within the 64-bit atomic_set here in the ppc64 section. r~
