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. Thanks, James
