On 6/21/2017 10:38 AM, Thomas Gleixner wrote: > On Wed, 21 Jun 2017, Tom Lendacky wrote: >> On 6/21/2017 2:16 AM, Thomas Gleixner wrote: >>> Why is this an unconditional function? Isn't the mask simply 0 when the MEM >>> ENCRYPT support is disabled? >> >> I made it unconditional because of the call from head_64.S. I can't make >> use of the C level static inline function and since the mask is not a >> variable if CONFIG_AMD_MEM_ENCRYPT is not configured (#defined to 0) I >> can't reference the variable directly. >> >> I could create a #define in head_64.S that changes this to load rax with >> the variable if CONFIG_AMD_MEM_ENCRYPT is configured or a zero if it's >> not or add a #ifdef at that point in the code directly. Thoughts on >> that? > > See below. > >>> That does not make any sense. Neither the call to sme_encrypt_kernel() nor >>> the following call to sme_get_me_mask(). >>> >>> __startup_64() is already C code, so why can't you simply call that from >>> __startup_64() in C and return the mask from there? >> >> I was trying to keep it explicit as to what was happening, but I can >> move those calls into __startup_64(). > > That's much preferred. And the return value wants to be documented in both > C and ASM code. Will do. > >> I'll still need the call to sme_get_me_mask() in the secondary_startup_64 >> path, though (depending on your thoughts to the above response). > > call verify_cpu > > movq $(init_top_pgt - __START_KERNEL_map), %rax > > So if you make that: > > /* > * Sanitize CPU configuration and retrieve the modifier > * for the initial pgdir entry which will be programmed > * into CR3. Depends on enabled SME encryption, normally 0. > */ > call __startup_secondary_64 > > addq $(init_top_pgt - __START_KERNEL_map), %rax > > You can hide that stuff in C-code nicely without adding any cruft to the > ASM code. > Moving the call to verify_cpu into the C-code might be quite a bit of change. Currently, the verify_cpu code is included code and not a global function. I can still do the __startup_secondary_64() function and then look to incorporate verify_cpu into both __startup_64() and __startup_secondary_64() as a post-patch to this series. At least the secondary path will have a base C routine to which modifications can be made in the future if needed. How does that sound? Thanks, Tom > Thanks, > > tglx >
