@@ -127,14 +127,24 @@ void kvm_apply_hyp_relocations(void);
#define __hyp_pa(x) (((phys_addr_t)(x)) + hyp_physvirt_offset)
+/*
+ * Convert a kernel VA into a HYP VA.
+ *
+ * Can be called from hyp or non-hyp context.
+ */
static __always_inline unsigned long __kern_hyp_va(unsigned long v)
{
+/*
+ * This #ifndef is an optimisation for when this is called from VHE hyp
+ * context. When called from a VHE non-hyp context, kvm_update_va_mask() will
+ * replace the instructions with `nop`s.
+ */
#ifndef __KVM_VHE_HYPERVISOR__
- asm volatile(ALTERNATIVE_CB("and %0, %0, #1\n"
- "ror %0, %0, #1\n"
- "add %0, %0, #0\n"
- "add %0, %0, #0, lsl 12\n"
- "ror %0, %0, #63\n",
+ asm volatile(ALTERNATIVE_CB("and %0, %0, #1\n" /* mask with va_mask */
+ "ror %0, %0, #1\n" /* rotate to the first tag bit */
+ "add %0, %0, #0\n" /* insert the low 12 bits of the tag */
+ "add %0, %0, #0, lsl 12\n" /* insert the top 12 bits of the tag */
+ "ror %0, %0, #63\n", /* rotate back */
ARM64_ALWAYS_SYSTEM,
kvm_update_va_mask)
: "+r" (v));
Document this function a little, to make it easier to understand. The assembly comments were copied from the kern_hyp_va asm macro. Signed-off-by: Joey Gouly <joey.gouly@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Oliver Upton <oliver.upton@linux.dev> --- arch/arm64/include/asm/kvm_mmu.h | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-)