On 04/12/17 14:13, Steve Capper wrote:
In save_elrsr(.), we use the following technique to ascertain the
address of the vgic global state:
(kern_hyp_va(&kvm_vgic_global_state))->nr_lr
For arm, kern_hyp_va(va) == va, and this call effectively compiles out.
For arm64, this call can be spurious as the address of kvm_vgic_global_state
will usually be determined by relative page/absolute page offset relocation
at link time. As the function is idempotent, having the call for arm64 does
not cause any problems.
Unfortunately, this is about to change for arm64 as we need to change
the logic of kern_hyp_va to allow for kernel addresses that are outside
the direct linear map.
This patch removes the call to kern_hyp_va, and ensures that correct
HYP addresses are computed via relative page offset addressing on arm64.
This is achieved by a custom accessor, hyp_address(.), which on arm is a
simple reference operator.
minor nit: I somehow feel that there word "symbol" should be part of the name of
the macro, to make it implicit that it can only be used on a symbol and not any
generic variable.
diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 08d3bb66c8b7..34a4ae906a97 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -25,6 +25,16 @@
#define __hyp_text __section(.hyp.text) notrace
+#define hyp_address(symbol) \
+({ \
+ typeof(&symbol) __ret; \
+ asm volatile( \
+ "adrp %[ptr], " #symbol "\n" \
+ "add %[ptr], %[ptr], :lo12:" #symbol "\n" \
+ : [ptr] "=r"(__ret)); \
+ __ret; \
+})
+
- addr = kern_hyp_va((kern_hyp_va(&kvm_vgic_global_state))->vcpu_base_va);
+ addr = kern_hyp_va(hyp_address(kvm_vgic_global_state)->vcpu_base_va);
e.g, Like here, why do we use hyp_address only for the kvm_vgic_global_state and not
the dereferenced value. Having a name, say, hyp_symbol_address() makes it clear.
Otherwise, looks good to me.
Suzuki
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