On 11/24/22 16:59, Huang, Kai wrote: > On Wed, 2022-11-23 at 15:56 -0800, Dave Hansen wrote: >> On 11/20/22 16:26, Kai Huang wrote: >>> + array_sz = ALIGN(tdmr_num * sizeof(u64), TDMR_INFO_PA_ARRAY_ALIGNMENT); >>> + tdmr_pa_array = kzalloc(array_sz, GFP_KERNEL); >> >> Just to be clear, all that chatter about alignment is because the >> *START* of the array has to be aligned. Right? > > Correct. > >> I see alignment for >> 'array_sz', but that's not the start of the array. >> >> tdmr_pa_array is the start of the array. Where is *THAT* aligned? > > The alignment is assumed to be guaranteed based on the Documentation you quoted > below. I'm feeling kinda dense today, being Thanksgiving and all. Could you please walk me through, step-by-step how you get kzalloc() to give you an allocation where the start address is 512-byte aligned? ... > Perhaps I should just allocate one page so it must be 512-byte aligned? > > /* > * TDMR_INFO entries are configured to the TDX module via an array > * of physical address of each TDMR_INFO. The TDX module requires > * the array itself to be 512-byte aligned. Just allocate a page > * to use it as the array so the alignment can be guaranteed. The > * page will be freed after TDH.SYS.CONFIG anyway. > */ Kai, I just plain can't believe at this point that comments like this are still being written. I _thought_ I was very clear before that if you have a constant, say: #define FOO_ALIGN 512 and you want to align foo, you can just do: foo = ALIGN(foo, FOO_ALIGN); You don't need to mention the 512-byte alignment again. The #define is good enough.
