Let's introduce a helper to probe read access (by actually reading a
piece of data of every page) and add a comment why this might not be
100% safe in all scenarios. Once we actually run into that issue, we'll
have to think of something else.
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
target/s390x/internal.h | 2 ++
target/s390x/mem_helper.c | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 36 insertions(+)
diff --git a/target/s390x/internal.h b/target/s390x/internal.h
index c243fa725b..bdb833c525 100644
--- a/target/s390x/internal.h
+++ b/target/s390x/internal.h
@@ -354,6 +354,8 @@ void ioinst_handle_sal(S390CPU *cpu, uint64_t reg1,
uintptr_t ra);
/* mem_helper.c */
target_ulong mmu_real2abs(CPUS390XState *env, target_ulong raddr);
+void probe_read_access(CPUS390XState *env, uint64_t addr, uint64_t len,
+ uintptr_t ra);
void probe_write_access(CPUS390XState *env, uint64_t addr, uint64_t len,
uintptr_t ra);
diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
index 7819aca15d..4e9d126e2c 100644
--- a/target/s390x/mem_helper.c
+++ b/target/s390x/mem_helper.c
@@ -2612,6 +2612,40 @@ uint32_t HELPER(cu42)(CPUS390XState *env, uint32_t r1,
uint32_t r2, uint32_t m3)
decode_utf32, encode_utf16);
}
+/*
+ * Make sure the read access is permitted and TLB entries are created. In
+ * very rare cases it might happen that the actual accesses might need
+ * new MMU translations. If the page tables were changed in between, we
+ * might still trigger a fault. However, this seems to barely happen, so we
+ * can ignore this for now.
+ */
+void probe_read_access(CPUS390XState *env, uint64_t addr, uint64_t len,
+ uintptr_t ra)
+{
+#ifdef CONFIG_USER_ONLY
+ if (!guest_addr_valid(addr) || !guest_addr_valid(addr + len - 1) ||
+ page_check_range(addr, len, PAGE_READ) < 0) {
+ s390_program_interrupt(env, PGM_ADDRESSING, ILEN_AUTO, ra);
+ }
+#else
+ while (len) {
+ const uint64_t pagelen = -(addr | -TARGET_PAGE_MASK);
+ const uint64_t curlen = MIN(pagelen, len);
+
+ cpu_ldub_data_ra(env, addr, ra);
+ addr = wrap_address(env, addr + curlen);
+ len -= curlen;
+ }
+#endif
+}
+
+/*
+ * Make sure the write access is permitted and TLB entries are created. In
+ * very rare cases it might happen that the actual accesses might need
+ * new MMU translations - especially, on LAP protected pages. If the page
+ * tables were changed in between, we might still trigger a fault. However,
+ * this seems to barely happen, so we can ignore this for now.
+ */
void probe_write_access(CPUS390XState *env, uint64_t addr, uint64_t len,
uintptr_t ra)
{
--
2.21.0
