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 <yoshikawa.takuya@xxxxxxxxxxxxx>
---
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
--
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