On Tue, 2023-06-27 at 12:51 +0300, kirill.shutemov@xxxxxxxxxxxxxxx wrote: > On Tue, Jun 27, 2023 at 02:12:38AM +1200, Kai Huang wrote: > > static int init_tdx_module(void) > > { > > + struct tdsysinfo_struct *sysinfo; > > + struct cmr_info *cmr_array; > > + int ret; > > + > > + /* > > + * Get the TDSYSINFO_STRUCT and CMRs from the TDX module. > > + * > > + * The buffers of the TDSYSINFO_STRUCT and the CMR array passed > > + * to the TDX module must be 1024-bytes and 512-bytes aligned > > + * respectively. Allocate one page to accommodate them both and > > + * also meet those alignment requirements. > > + */ > > + sysinfo = (struct tdsysinfo_struct *)__get_free_page(GFP_KERNEL); > > + if (!sysinfo) > > + return -ENOMEM; > > + cmr_array = (struct cmr_info *)((unsigned long)sysinfo + PAGE_SIZE / 2); > > + > > + BUILD_BUG_ON(PAGE_SIZE / 2 < TDSYSINFO_STRUCT_SIZE); > > + BUILD_BUG_ON(PAGE_SIZE / 2 < sizeof(struct cmr_info) * MAX_CMRS); > > This works, but why not just use slab for this? kmalloc has 512 and 1024 > pools already and you won't waste memory for rounding up. > > Something like this: > > sysinfo = kmalloc(TDSYSINFO_STRUCT_SIZE, GFP_KERNEL); > if (!sysinfo) > return -ENOMEM; > > cmr_array_size = sizeof(struct cmr_info) * MAX_CMRS; > > /* CMR array has to be 512-aligned */ > cmr_array_size = round_up(cmr_array_size, 512); Should we define a macro for 512 +#define CMR_INFO_ARRAY_ALIGNMENT 512 And get rid of this comment? AFAICT Dave didn't like such comment mentioning 512-bytes aligned if we have a macro for that. > > cmr_array = kmalloc(cmr_array_size, GFP_KERNEL); > if (!cmr_array) { > kfree(sysinfo); > return -ENOMEM; > } > > ? > I confess the reason I used __get_free_page() was to avoid having to allocate twice, and in case of failure, I need to handle additional memory free. But I can do if you think it's clearer? I wouldn't worry about wasting memory. The buffer is freed anyway for now. Long-termly it's just 4K.