KVM: arm64: selftests: Add MMIO readl/writel support

Define the readl() and writel() functions for the guests to
access (4-byte) the MMIO region.

The routines, and their dependents, are inspired from the kernel's
arch/arm64/include/asm/io.h and arch/arm64/include/asm/barrier.h.
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211007233439.1826892-2-rananta@google.com

tools/testing/selftests/kvm/include/aarch64/processor.h

@@ -9,6 +9,7 @@
 
 #include "kvm_util.h"
 #include <linux/stringify.h>
+#include <linux/types.h>
 
 
 #define ARM64_CORE_REG(x) (KVM_REG_ARM64 | KVM_REG_SIZE_U64 | \
@@ -131,5 +132,48 @@ void vm_install_sync_handler(struct kvm_vm *vm,
 })
 
 #define isb()		asm volatile("isb" : : : "memory")
+#define dsb(opt)	asm volatile("dsb " #opt : : : "memory")
+#define dmb(opt)	asm volatile("dmb " #opt : : : "memory")
+
+#define dma_wmb()	dmb(oshst)
+#define __iowmb()	dma_wmb()
+
+#define dma_rmb()	dmb(oshld)
+
+#define __iormb(v)							\
+({									\
+	unsigned long tmp;						\
+									\
+	dma_rmb();							\
+									\
+	/*								\
+	 * Courtesy of arch/arm64/include/asm/io.h:			\
+	 * Create a dummy control dependency from the IO read to any	\
+	 * later instructions. This ensures that a subsequent call	\
+	 * to udelay() will be ordered due to the ISB in __delay().	\
+	 */								\
+	asm volatile("eor	%0, %1, %1\n"				\
+		     "cbnz	%0, ."					\
+		     : "=r" (tmp) : "r" ((unsigned long)(v))		\
+		     : "memory");					\
+})
+
+static __always_inline void __raw_writel(u32 val, volatile void *addr)
+{
+	asm volatile("str %w0, [%1]" : : "rZ" (val), "r" (addr));
+}
+
+static __always_inline u32 __raw_readl(const volatile void *addr)
+{
+	u32 val;
+	asm volatile("ldr %w0, [%1]" : "=r" (val) : "r" (addr));
+	return val;
+}
+
+#define writel_relaxed(v,c)	((void)__raw_writel((__force u32)cpu_to_le32(v),(c)))
+#define readl_relaxed(c)	({ u32 __r = le32_to_cpu((__force __le32)__raw_readl(c)); __r; })
+
+#define writel(v,c)		({ __iowmb(); writel_relaxed((v),(c));})
+#define readl(c)		({ u32 __v = readl_relaxed(c); __iormb(__v); __v; })
 
 #endif /* SELFTEST_KVM_PROCESSOR_H */