On Tue, 2009-05-12 at 12:45 -0600, Alex Williamson wrote: > On Mon, 2009-05-11 at 12:00 +0000, Yang, Sheng wrote: > > On Friday 08 May 2009 06:22:20 Alex Williamson wrote: > > > + /* Round the number of GSIs supported to a 4 byte > > > + * value so we can search it using ints and ffs */ > > > + i = kvm_get_gsi_count(kvm) & ~0x1f; > > > + kvm->used_gsi_bitmap = malloc(i >> 3); > > > > 3 or 5? > > 3, ie. /8 (bits to bytes) > > > I am a little confused by these magic numbers, including 0x1f... > > The 5 shift gives us the index into the array of ints, the 0x1f gives us > the bit index into a specific int. This is very similar to the code in > hw/acpi.c. > > > I think there are something can indicate the length of unsigned long in > > QEmu(sorry, can't find it now...), so how about using ffsl() and get other > > constants based on it? > > We'd probably want to use ffsll() so we can ignore 32b vs 64b longs. > There's HOST_LONG_BITS, but that doesn't actually help defining a shift > value. Thanks,
Hmm, neither ffsl() or ffsll() are standard. I'm inclined to stick with 32bits. We'll likely only be using the first index on x86_64 anyway (2nd on ia64). Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
