Re: [Qemu-devel] [PATCH v2 18/28] s390x/tcg: MVC: Fault-safe handling on destructive overlaps

[Richard Henderson]

On 9/6/19 3:57 AM, David Hildenbrand wrote:
> +static S390Access access_prepare(CPUS390XState *env, vaddr vaddr, int size,
> + MMUAccessType access_type, uintptr_t ra)
> +{
> +int mmu_idx = cpu_mmu_index(env, false);
> +
> +return access_prepare_idx(env, vaddr, size, access_type, mmu_idx, ra);
> +}
> +
>  static void access_memset_idx(CPUS390XState *env, vaddr vaddr, uint8_t byte,
>int size, int mmu_idx, uintptr_t ra)
>  {
> @@ -420,9 +428,13 @@ static uint32_t do_helper_mvc(CPUS390XState *env, 
> uint32_t l, uint64_t dest,
>  } else if (!is_destructive_overlap(env, dest, src, l)) {
>  access_memmove(env, dest, src, l, ra);
>  } else {
> +S390Access srca = access_prepare(env, src, l, MMU_DATA_LOAD, ra);
> +S390Access desta = access_prepare(env, dest, l, MMU_DATA_STORE, ra);

I was just thinking it might be better to drop the non-idx functions:
access_prepare, access_memset, access_memmove.  What this is leading to is
computation of cpu_mmu_index multiple times, as here.

It could just as easily be hoisted to the top of do_helper_mvc and used in all
of the sub-cases.

That said, the code here is correct so
Reviewed-by: Richard Henderson 

r~

[Qemu-devel] [PATCH v2 18/28] s390x/tcg: MVC: Fault-safe handling on destructive overlaps

[David Hildenbrand]

The last remaining bit for MVC is handling destructive overlaps in a
fault-safe way.

Signed-off-by: David Hildenbrand 
---
 target/s390x/mem_helper.c | 16 ++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
index 2607dd1677..f636f3a011 100644
--- a/target/s390x/mem_helper.c
+++ b/target/s390x/mem_helper.c
@@ -145,6 +145,14 @@ static S390Access access_prepare_idx(CPUS390XState *env, 
vaddr vaddr, int size,
 return access;
 }
 
+static S390Access access_prepare(CPUS390XState *env, vaddr vaddr, int size,
+ MMUAccessType access_type, uintptr_t ra)
+{
+int mmu_idx = cpu_mmu_index(env, false);
+
+return access_prepare_idx(env, vaddr, size, access_type, mmu_idx, ra);
+}
+
 static void access_memset_idx(CPUS390XState *env, vaddr vaddr, uint8_t byte,
   int size, int mmu_idx, uintptr_t ra)
 {
@@ -420,9 +428,13 @@ static uint32_t do_helper_mvc(CPUS390XState *env, uint32_t 
l, uint64_t dest,
 } else if (!is_destructive_overlap(env, dest, src, l)) {
 access_memmove(env, dest, src, l, ra);
 } else {
+S390Access srca = access_prepare(env, src, l, MMU_DATA_LOAD, ra);
+S390Access desta = access_prepare(env, dest, l, MMU_DATA_STORE, ra);
+
 for (i = 0; i < l; i++) {
-uint8_t x = cpu_ldub_data_ra(env, src + i, ra);
-cpu_stb_data_ra(env, dest + i, x, ra);
+uint8_t byte = access_get_byte(env, &srca, i, ra);
+
+access_set_byte(env, &desta, i, byte, ra);
 }
 }
 
-- 
2.21.0