[PATCH v3 08/23] arm64: KVM: VHE: Patch out kern_hyp_va

Marc Zyngier
2016-02-03T18:07:44Z

The kern_hyp_va macro is pretty meaninless with VHE, as there is
only one mapping - the kernel one.

In order to keep the code readable and efficient, use runtime
patching to replace the 'and' instruction used to compute the VA
with a 'nop'.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/include/asm/kvm_mmu.h | 12 +++++++++++-
arch/arm64/kvm/hyp/hyp.h | 25 ++++++++++++++++++++++---
2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 7364339..9a9318a 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -23,13 +23,16 @@
#include <asm/cpufeature.h>

/*
- * As we only have the TTBR0_EL2 register, we cannot express
+ * As ARMv8.0 only has the TTBR0_EL2 register, we cannot express
* "negative" addresses. This makes it impossible to directly share
* mappings with the kernel.
*
* Instead, give the HYP mode its own VA region at a fixed offset from
* the kernel by just masking the top bits (which are all ones for a
* kernel address).
+ *
+ * ARMv8.1 (using VHE) does have a TTBR1_EL2, and doesn't use these
+ * macros (the entire kernel runs at EL2).
*/
#define HYP_PAGE_OFFSET_SHIFT VA_BITS
#define HYP_PAGE_OFFSET_MASK ((UL(1) << HYP_PAGE_OFFSET_SHIFT) - 1)
@@ -56,12 +59,19 @@

#ifdef __ASSEMBLY__

+#include <asm/alternative.h>
+#include <asm/cpufeature.h>
+
/*
* Convert a kernel VA into a HYP VA.
* reg: VA to be converted.
*/
.macro kern_hyp_va reg
+alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
and \reg, \reg, #HYP_PAGE_OFFSET_MASK
+alternative_else
+ nop
+alternative_endif
.endm

#else
diff --git a/arch/arm64/kvm/hyp/hyp.h b/arch/arm64/kvm/hyp/hyp.h
index fb27517..fc502f3 100644
--- a/arch/arm64/kvm/hyp/hyp.h
+++ b/arch/arm64/kvm/hyp/hyp.h
@@ -25,9 +25,28 @@

#define __hyp_text __section(.hyp.text) notrace

-#define kern_hyp_va(v) (typeof(v))((unsigned long)(v) & HYP_PAGE_OFFSET_MASK)
-#define hyp_kern_va(v) (typeof(v))((unsigned long)(v) - HYP_PAGE_OFFSET \
- + PAGE_OFFSET)
+static inline unsigned long __kern_hyp_va(unsigned long v)
+{
+ asm volatile(ALTERNATIVE("and %0, %0, %1",
+ "nop",
+ ARM64_HAS_VIRT_HOST_EXTN)
+ : "+r" (v) : "i" (HYP_PAGE_OFFSET_MASK));
+ return v;
+}
+
+#define kern_hyp_va(v) (typeof(v))(__kern_hyp_va((unsigned long)(v)))
+
+static inline unsigned long __hyp_kern_va(unsigned long v)
+{
+ u64 offset = PAGE_OFFSET - HYP_PAGE_OFFSET;
+ asm volatile(ALTERNATIVE("add %0, %0, %1",
+ "nop",
+ ARM64_HAS_VIRT_HOST_EXTN)
+ : "+r" (v) : "r" (offset));
+ return v;
+}
+
+#define hyp_kern_va(v) (typeof(v))(__hyp_kern_va((unsigned long)(v)))

/**
* hyp_alternate_select - Generates patchable code sequences that are
--
2.1.4