accel/tcg: Add 'size' param to probe_access_flags()

probe_access_flags() as it is today uses probe_access_full(), which in
turn uses probe_access_internal() with size = 0. probe_access_internal()
then uses the size to call the tlb_fill() callback for the given CPU.
This size param ('fault_size' as probe_access_internal() calls it) is
ignored by most existing .tlb_fill callback implementations, e.g.
arm_cpu_tlb_fill(), ppc_cpu_tlb_fill(), x86_cpu_tlb_fill() and
mips_cpu_tlb_fill() to name a few.

But RISC-V riscv_cpu_tlb_fill() actually uses it. The 'size' parameter
is used to check for PMP (Physical Memory Protection) access. This is
necessary because PMP does not make any guarantees about all the bytes
of the same page having the same permissions, i.e. the same page can
have different PMP properties, so we're forced to make sub-page range
checks. To allow RISC-V emulation to do a probe_acess_flags() that
covers PMP, we need to either add a 'size' param to the existing
probe_acess_flags() or create a new interface (e.g.
probe_access_range_flags).

There are quite a few probe_* APIs already, so let's add a 'size' param
to probe_access_flags() and re-use this API. This is done by open coding
what probe_access_full() does inside probe_acess_flags() and passing the
'size' param to probe_acess_internal(). Existing probe_access_flags()
callers use size = 0 to not change their current API usage. 'size' is
asserted to enforce single page access like probe_access() already does.

No behavioral changes intended.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-Id: <20230223234427.521114-2-dbarboza@ventanamicro.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

accel/stubs/tcg-stub.c

@@ -25,7 +25,7 @@ void tcg_flush_jmp_cache(CPUState *cpu)
 {
 }
 
-int probe_access_flags(CPUArchState *env, target_ulong addr,
+int probe_access_flags(CPUArchState *env, target_ulong addr, int size,
                        MMUAccessType access_type, int mmu_idx,
                        bool nonfault, void **phost, uintptr_t retaddr)
 {

accel/tcg/cputlb.c

@@ -1606,14 +1606,25 @@ int probe_access_full(CPUArchState *env, target_ulong addr,
     return flags;
 }
 
-int probe_access_flags(CPUArchState *env, target_ulong addr,
+int probe_access_flags(CPUArchState *env, target_ulong addr, int size,
                        MMUAccessType access_type, int mmu_idx,
                        bool nonfault, void **phost, uintptr_t retaddr)
 {
     CPUTLBEntryFull *full;
+    int flags;
 
-    return probe_access_full(env, addr, access_type, mmu_idx,
-                             nonfault, phost, &full, retaddr);
+    g_assert(-(addr | TARGET_PAGE_MASK) >= size);
+
+    flags = probe_access_internal(env, addr, size, access_type, mmu_idx,
+                                  nonfault, phost, &full, retaddr);
+
+    /* Handle clean RAM pages. */
+    if (unlikely(flags & TLB_NOTDIRTY)) {
+        notdirty_write(env_cpu(env), addr, 1, full, retaddr);
+        flags &= ~TLB_NOTDIRTY;
+    }
+
+    return flags;
 }
 
 void *probe_access(CPUArchState *env, target_ulong addr, int size,

accel/tcg/user-exec.c

@@ -761,13 +761,14 @@ static int probe_access_internal(CPUArchState *env, target_ulong addr,
     cpu_loop_exit_sigsegv(env_cpu(env), addr, access_type, maperr, ra);
 }
 
-int probe_access_flags(CPUArchState *env, target_ulong addr,
+int probe_access_flags(CPUArchState *env, target_ulong addr, int size,
                        MMUAccessType access_type, int mmu_idx,
                        bool nonfault, void **phost, uintptr_t ra)
 {
     int flags;
 
-    flags = probe_access_internal(env, addr, 0, access_type, nonfault, ra);
+    g_assert(-(addr | TARGET_PAGE_MASK) >= size);
+    flags = probe_access_internal(env, addr, size, access_type, nonfault, ra);
     *phost = flags ? NULL : g2h(env_cpu(env), addr);
     return flags;
 }

include/exec/exec-all.h

@@ -447,6 +447,7 @@ static inline void *probe_read(CPUArchState *env, target_ulong addr, int size,
  * probe_access_flags:
  * @env: CPUArchState
  * @addr: guest virtual address to look up
+ * @size: size of the access
  * @access_type: read, write or execute permission
  * @mmu_idx: MMU index to use for lookup
  * @nonfault: suppress the fault
@@ -461,7 +462,7 @@ static inline void *probe_read(CPUArchState *env, target_ulong addr, int size,
  * 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,
+int probe_access_flags(CPUArchState *env, target_ulong addr, int size,
                        MMUAccessType access_type, int mmu_idx,
                        bool nonfault, void **phost, uintptr_t retaddr);
 

semihosting/uaccess.c

@@ -37,7 +37,7 @@ ssize_t softmmu_strlen_user(CPUArchState *env, target_ulong addr)
         /* Find the number of bytes remaining in the page. */
         left_in_page = TARGET_PAGE_SIZE - (addr & ~TARGET_PAGE_MASK);
 
-        flags = probe_access_flags(env, addr, MMU_DATA_LOAD,
+        flags = probe_access_flags(env, addr, 0, MMU_DATA_LOAD,
                                    mmu_idx, true, &h, 0);
         if (flags & TLB_INVALID_MASK) {
             return -1;

target/arm/ptw.c

@@ -411,7 +411,7 @@ static uint64_t arm_casq_ptw(CPUARMState *env, uint64_t old_val,
         void *discard;
 
         env->tlb_fi = fi;
-        flags = probe_access_flags(env, ptw->out_virt, MMU_DATA_STORE,
+        flags = probe_access_flags(env, ptw->out_virt, 0, MMU_DATA_STORE,
                                    arm_to_core_mmu_idx(ptw->in_ptw_idx),
                                    true, &discard, 0);
         env->tlb_fi = NULL;

target/arm/tcg/sve_helper.c

@@ -5352,7 +5352,7 @@ bool sve_probe_page(SVEHostPage *info, bool nofault, CPUARMState *env,
     addr = useronly_clean_ptr(addr);
 
 #ifdef CONFIG_USER_ONLY
-    flags = probe_access_flags(env, addr, access_type, mmu_idx, nofault,
+    flags = probe_access_flags(env, addr, 0, access_type, mmu_idx, nofault,
                                &info->host, retaddr);
 #else
     CPUTLBEntryFull *full;

target/s390x/tcg/mem_helper.c

@@ -145,7 +145,7 @@ static inline int s390_probe_access(CPUArchState *env, target_ulong addr,
                                     int mmu_idx, bool nonfault,
                                     void **phost, uintptr_t ra)
 {
-    int flags = probe_access_flags(env, addr, access_type, mmu_idx,
+    int flags = probe_access_flags(env, addr, 0, access_type, mmu_idx,
                                    nonfault, phost, ra);
 
     if (unlikely(flags & TLB_INVALID_MASK)) {