On 3/27/2025 5:48 PM, Thomas Gleixner wrote: > On Thu, Mar 27 2025 at 16:47, Neeraj Upadhyay wrote: >> On 3/27/2025 3:57 PM, Thomas Gleixner wrote: >>> The relevant registers are starting at regs[SAVIC_ALLOWED_IRR]. Due to >>> the 16-byte alignment the vector number obviously cannot be used for >>> linear bitmap addressing. >>> >>> But the resulting bit number can be trivially calculated with: >>> >>> bit = vector + 32 * (vector / 32); >>> >> >> Somehow, this math is not working for me. I will think more on how this >> works. From what I understand, bit number is: >> >> bit = vector % 32 + (vector / 32) * 16 * 8 >> >> So, for example, vector number 32, bit number need to be 128. >> With you formula, it comes as 64. > > Duh. I did the math for 8 byte alignment. But for 16 byte it's obviously > exactly the same formula just with a different multiplicator: > > bit = vector + 96 * (vector / 32); > > No? > Ah ok. Got it. Makes sense. 96 * (vector / 32) counts all unused space. - Neeraj
