Although returning -1 should be likely according to the likely(), the ASSERT in apic_find_highest_irr() will be triggered in such a case. It seems that this optimization is not working as expected.
This patch simplifies the logic to mitigate this issue: search for the first non-zero word in a for loop and then use __fls() if found. When nothing found, we are out of the loop, so we can just return -1. Signed-off-by: Takuya Yoshikawa <[email protected]> --- arch/x86/kvm/lapic.c | 18 ++++++++++-------- 1 files changed, 10 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 18d149d..5eb4dde 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -208,16 +208,18 @@ static unsigned int apic_lvt_mask[APIC_LVT_NUM] = { static int find_highest_vector(void *bitmap) { - u32 *word = bitmap; - int word_offset = MAX_APIC_VECTOR >> 5; + u32 *p = bitmap; + u32 word; + int word_offset; - while ((word_offset != 0) && (word[(--word_offset) << 2] == 0)) - continue; + for (word_offset = (MAX_APIC_VECTOR >> 5) - 1; + word_offset >= 0; --word_offset) { + word = p[word_offset << 2]; + if (word) + return __fls(word) + (word_offset << 5); + } - if (likely(!word_offset && !word[0])) - return -1; - else - return fls(word[word_offset << 2]) - 1 + (word_offset << 5); + return -1; } static u8 count_vectors(void *bitmap) -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
