From: Armin Wolf > Sent: 19 February 2022 21:10 > > The new assembly code works on both 32 bit and 64 bit > cpus and allows for more compiler optimisations by not > requiring smm_regs to be packed I'm intrigued about the __packed.. Prior to 5.17-rc1 __packed was only applied to the fields after 'eax'. This actually has no effect (on any architecture) because there is no padding to remove - so all the later fields are still assumed to be 32bit aligned. 5.17-rc1 (565210c781201) moved the __packed to the end of the structure. AFAICT this structure is only ever used in one file and for on-stack items. It will always actually be aligned and is only read by the code in the file - so why was it ever marked __packed at all! On x86 it would make no difference anyway. I can only guess it was to ensure that the asm code didn't go 'wrong' because of the compiler adding 'random' padding. That isn't what __packed is for at all. The linux kernel requires that the compiler doesn't add 'random' padding - even if the C standard might allow it. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
