diff options
Diffstat (limited to 'arch/arm64/include')
| -rw-r--r-- | arch/arm64/include/asm/virt.h | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h index 1466d14c664d..1569c3a0d794 100644 --- a/arch/arm64/include/asm/virt.h +++ b/arch/arm64/include/asm/virt.h @@ -19,9 +19,14 @@ #define __ASM__VIRT_H /* - * The arm64 hcall implementation uses x0 to specify the hcall type. A value - * less than 0xfff indicates a special hcall, such as get/set vector. - * Any other value is used as a pointer to the function to call. + * The arm64 hcall implementation uses x0 to specify the hcall + * number. A value less than HVC_STUB_HCALL_NR indicates a special + * hcall, such as set vector. Any other value is handled in a + * hypervisor specific way. + * + * The hypercall is allowed to clobber any of the caller-saved + * registers (x0-x18), so it is advisable to use it through the + * indirection of a function call (as implemented in hyp-stub.S). */ /* HVC_GET_VECTORS - Return the value of the vbar_el2 register. */ |