accel/tcg: Add probe_access_flags

This new interface will allow targets to probe for a page
and then handle watchpoints themselves.  This will be most
useful for vector predicated memory operations, where one
page lookup can be used for many operations, and one test
can avoid many watchpoint checks.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200508154359.7494-6-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 34 insertions, 1 deletions

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 49384bb..43ddcf0 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -328,7 +328,18 @@ CPUArchState *cpu_copy(CPUArchState *env);
      | CPU_INTERRUPT_TGT_EXT_3   \
      | CPU_INTERRUPT_TGT_EXT_4)
 
-#if !defined(CONFIG_USER_ONLY)
+#ifdef CONFIG_USER_ONLY
+
+/*
+ * Allow some level of source compatibility with softmmu.  We do not
+ * support any of the more exotic features, so only invalid pages may
+ * be signaled by probe_access_flags().
+ */
+#define TLB_INVALID_MASK    (1 << (TARGET_PAGE_BITS_MIN - 1))
+#define TLB_MMIO            0
+#define TLB_WATCHPOINT      0
+
+#else
 
 /*
  * Flags stored in the low bits of the TLB virtual address.
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index d656a1f..8792bea 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -362,6 +362,28 @@ static inline void *probe_read(CPUArchState *env, target_ulong addr, int size,
     return probe_access(env, addr, size, MMU_DATA_LOAD, mmu_idx, retaddr);
 }
 
+/**
+ * probe_access_flags:
+ * @env: CPUArchState
+ * @addr: guest virtual address to look up
+ * @access_type: read, write or execute permission
+ * @mmu_idx: MMU index to use for lookup
+ * @nonfault: suppress the fault
+ * @phost: return value for host address
+ * @retaddr: return address for unwinding
+ *
+ * Similar to probe_access, loosely returning the TLB_FLAGS_MASK for
+ * the page, and storing the host address for RAM in @phost.
+ *
+ * If @nonfault is set, do not raise an exception but return TLB_INVALID_MASK.
+ * Do not handle watchpoints, but include TLB_WATCHPOINT in the returned flags.
+ * Do handle clean pages, so exclude TLB_NOTDIRY from the returned flags.
+ * For simplicity, all "mmio-like" flags are folded to TLB_MMIO.
+ */
+int probe_access_flags(CPUArchState *env, target_ulong addr,
+                       MMUAccessType access_type, int mmu_idx,
+                       bool nonfault, void **phost, uintptr_t retaddr);
+
 #define CODE_GEN_ALIGN           16 /* must be >= of the size of a icache line */
 
 /* Estimated block size for TB allocation.  */