On 21/03/17 17:25, James Morse wrote: > Hi Catalin, > > On 21/03/17 17:04, Catalin Marinas wrote: >> On Mon, Mar 06, 2017 at 02:24:34PM +0000, Marc Zyngier wrote: >>> Let's define a new stub hypercall that resets the HYP configuration >>> to its default: hyp-stub vectors, and MMU disabled. >>> >>> Of course, for the hyp-stub itself, this is a trivial no-op. >>> Hypervisors will have a bit more work to do. >>> >>> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> >>> --- >>> arch/arm64/include/asm/virt.h | 9 +++++++++ >>> arch/arm64/kernel/hyp-stub.S | 13 ++++++++++++- >>> 2 files changed, 21 insertions(+), 1 deletion(-) >> [...] >>> +ENTRY(__hyp_reset_vectors) >>> + str lr, [sp, #-16]! >>> + mov x0, #HVC_RESET_VECTORS >>> + hvc #0 >>> + ldr lr, [sp], #16 >>> + ret >>> +ENDPROC(__hyp_reset_vectors) >> >> Why do we need to specifically preserve lr across the hvc call? Is it >> corrupted by the EL2 code (if yes, are other caller-saved registers that >> need preserving)? I don't see something similar in the arch/arm code. > > Kexec on arm64 needed a register to clobber in the hyp-stub's el1_sync code. We > wanted to preserve all the registers so soft_restart() could look more like a > function call. I don't think we need this anymore. Once we enter __cpu_soft_restart(), there is no turning back. Or am I missing something else? Thanks, M. -- Jazz is not dead. It just smells funny...
