target-arm: Split NO_MIGRATE into ALIAS and NO_RAW

We currently mark ARM coprocessor/system register definitions with
the flag ARM_CP_NO_MIGRATE for two different reasons:
1) register is an alias on to state that's also visible via
   some other register, and that other register is the one
   responsible for migrating the state
2) register is not actually state at all (for instance the TLB
   or cache maintenance operation "registers") and it makes no
   sense to attempt to migrate it or otherwise access the raw state

This works fine for identifying which registers should be ignored
when performing migration, but we also use the same functions for
synchronizing system register state between QEMU and the kernel
when using KVM. In this case we don't want to try to sync state
into registers in category 2, but we do want to sync into registers
in category 1, because the kernel might have picked a different
one of the aliases as its choice for which one to expose for
migration. (In particular, on 32 bit hosts the kernel will
expose the state in the AArch32 version of the register, but
TCG's convention is to mark the AArch64 version as the version
to migrate, even if the CPU being emulated happens to be 32 bit,
so almost all system registers will hit this issue now that we've
added AArch64 system emulation.)

Fix this by splitting the NO_MIGRATE flag in two (ALIAS and NO_RAW)
corresponding to the two different reasons we might not want to
migrate a register. When setting up the TCG list of registers to
migrate we honour both flags; when populating the list from KVM,
only ignore registers which are NO_RAW.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NGreg Bellows <greg.bellows@linaro.org>
Message-id: 1422282372-13735-2-git-send-email-peter.maydell@linaro.org
[PMM: changed ARM_CP_NO_MIGRATE to ARM_CP_ALIAS on new SP_EL1 and
 SP_EL2 reginfo stanzas since there was a (semantic) merge conflict
 with the patchset that added those]

target-arm/cpu.h

@@ -1110,8 +1110,14 @@ static inline uint64_t cpreg_to_kvm_id(uint32_t cpregid)
  * a register definition to override a previous definition for the
  * same (cp, is64, crn, crm, opc1, opc2) tuple: either the new or the
  * old must have the OVERRIDE bit set.
- * NO_MIGRATE indicates that this register should be ignored for migration;
- * (eg because any state is accessed via some other coprocessor register).
+ * ALIAS indicates that this register is an alias view of some underlying
+ * state which is also visible via another register, and that the other
+ * register is handling migration; registers marked ALIAS will not be migrated
+ * but may have their state set by syncing of register state from KVM.
+ * NO_RAW indicates that this register has no underlying state and does not
+ * support raw access for state saving/loading; it will not be used for either
+ * migration or KVM state synchronization. (Typically this is for "registers"
+ * which are actually used as instructions for cache maintenance and so on.)
  * IO indicates that this register does I/O and therefore its accesses
  * need to be surrounded by gen_io_start()/gen_io_end(). In particular,
  * registers which implement clocks or timers require this.
@@ -1121,8 +1127,9 @@ static inline uint64_t cpreg_to_kvm_id(uint32_t cpregid)
 #define ARM_CP_64BIT 4
 #define ARM_CP_SUPPRESS_TB_END 8
 #define ARM_CP_OVERRIDE 16
-#define ARM_CP_NO_MIGRATE 32
+#define ARM_CP_ALIAS 32
 #define ARM_CP_IO 64
+#define ARM_CP_NO_RAW 128
 #define ARM_CP_NOP (ARM_CP_SPECIAL | (1 << 8))
 #define ARM_CP_WFI (ARM_CP_SPECIAL | (2 << 8))
 #define ARM_CP_NZCV (ARM_CP_SPECIAL | (3 << 8))
@@ -1132,7 +1139,7 @@ static inline uint64_t cpreg_to_kvm_id(uint32_t cpregid)
 /* Used only as a terminator for ARMCPRegInfo lists */
 #define ARM_CP_SENTINEL 0xffff
 /* Mask of only the flag bits in a type field */
-#define ARM_CP_FLAG_MASK 0x7f
+#define ARM_CP_FLAG_MASK 0xff
 
 /* Valid values for ARMCPRegInfo state field, indicating which of
  * the AArch32 and AArch64 execution states this register is visible in.