[Qemu-devel] [PATCH v1 10/22] RISC-V: Hold rcu_read_lock when accessing memory

[Michael Clark]

>From reading other code that accesses memory regions directly,
it appears that the rcu_read_lock needs to be held. Note: the
original code for accessing RAM directly was added because
there is no other way to use atomic_cmpxchg easily.

Signed-off-by: Michael Clark 
Signed-off-by: Stefan O'Rear 
Signed-off-by: Palmer Dabbelt 
---
 target/riscv/helper.c | 4 
 1 file changed, 4 insertions(+)

diff --git a/target/riscv/helper.c b/target/riscv/helper.c
index 02cbcea..228933c 100644
--- a/target/riscv/helper.c
+++ b/target/riscv/helper.c
@@ -209,6 +209,7 @@ restart:
as the PTE is no longer valid */
 MemoryRegion *mr;
 hwaddr l = sizeof(target_ulong), addr1;
+rcu_read_lock();
 mr = address_space_translate(cs->as, pte_addr,
 , , false);
 if (memory_access_is_direct(mr, true)) {
@@ -222,16 +223,19 @@ restart:
 target_ulong old_pte =
 atomic_cmpxchg(pte_pa, pte, updated_pte);
 if (old_pte != pte) {
+rcu_read_unlock();
 goto restart;
 } else {
 pte = updated_pte;
 }
 #endif
 } else {
+rcu_read_unlock();
 /* misconfigured PTE in ROM (AD bits are not preset) or
  * PTE is in IO space and can't be updated atomically */
 return TRANSLATE_FAIL;
 }
+rcu_read_unlock();
 }
 
 /* for superpage mappings, make a fake leaf PTE for the TLB's
-- 
2.7.0

[Qemu-devel] [PATCH v1 10/22] RISC-V: Hold rcu_read_lock when accessing memory

[Michael Clark]

>From reading other code that accesses memory regions directly,
it appears that the rcu_read_lock needs to be held. Note: the
original code for accessing RAM directly was added because
there is no other way to use atomic_cmpxchg easily.

Signed-off-by: Michael Clark 
Signed-off-by: Stefan O'Rear 
Signed-off-by: Palmer Dabbelt 
---
 target/riscv/helper.c | 4 
 1 file changed, 4 insertions(+)

diff --git a/target/riscv/helper.c b/target/riscv/helper.c
index 02cbcea..228933c 100644
--- a/target/riscv/helper.c
+++ b/target/riscv/helper.c
@@ -209,6 +209,7 @@ restart:
as the PTE is no longer valid */
 MemoryRegion *mr;
 hwaddr l = sizeof(target_ulong), addr1;
+rcu_read_lock();
 mr = address_space_translate(cs->as, pte_addr,
 , , false);
 if (memory_access_is_direct(mr, true)) {
@@ -222,16 +223,19 @@ restart:
 target_ulong old_pte =
 atomic_cmpxchg(pte_pa, pte, updated_pte);
 if (old_pte != pte) {
+rcu_read_unlock();
 goto restart;
 } else {
 pte = updated_pte;
 }
 #endif
 } else {
+rcu_read_unlock();
 /* misconfigured PTE in ROM (AD bits are not preset) or
  * PTE is in IO space and can't be updated atomically */
 return TRANSLATE_FAIL;
 }
+rcu_read_unlock();
 }
 
 /* for superpage mappings, make a fake leaf PTE for the TLB's
-- 
2.7.0