Re: [Qemu-devel] [PATCH v2 20/28] s390x/tcg: OC: Fault-safe handling

[David Hildenbrand]

On 11.09.19 23:26, Richard Henderson wrote:
> On 9/6/19 3:57 AM, David Hildenbrand wrote:
>> +srca2 = access_prepare(env, dest, l, MMU_DATA_LOAD, ra);
>> +desta = access_prepare(env, dest, l, MMU_DATA_STORE, ra);
> 
> We should find a way to perform this in one step.
> RWM isn't uncommon...

Yes, like converting MMU_* into flags we can then process in probe_access().

> 
> That said,
> Reviewed-by: Richard Henderson 
> 
> r~
> 


-- 

Thanks,

David / dhildenb

Re: [Qemu-devel] [PATCH v2 20/28] s390x/tcg: OC: Fault-safe handling

[Richard Henderson]

On 9/6/19 3:57 AM, David Hildenbrand wrote:
> +srca2 = access_prepare(env, dest, l, MMU_DATA_LOAD, ra);
> +desta = access_prepare(env, dest, l, MMU_DATA_STORE, ra);

We should find a way to perform this in one step.
RWM isn't uncommon...

That said,
Reviewed-by: Richard Henderson 

r~

[Qemu-devel] [PATCH v2 20/28] s390x/tcg: OC: Fault-safe handling

[David Hildenbrand]

We can process a maximum of 256 bytes, crossing two pages.

Signed-off-by: David Hildenbrand 
---
 target/s390x/mem_helper.c | 16 
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
index 0366cbc753..ff57fec8de 100644
--- a/target/s390x/mem_helper.c
+++ b/target/s390x/mem_helper.c
@@ -385,17 +385,25 @@ uint32_t HELPER(xc)(CPUS390XState *env, uint32_t l, 
uint64_t dest,
 static uint32_t do_helper_oc(CPUS390XState *env, uint32_t l, uint64_t dest,
  uint64_t src, uintptr_t ra)
 {
+S390Access srca1, srca2, desta;
 uint32_t i;
 uint8_t c = 0;
 
 HELPER_LOG("%s l %d dest %" PRIx64 " src %" PRIx64 "\n",
__func__, l, dest, src);
 
-for (i = 0; i <= l; i++) {
-uint8_t x = cpu_ldub_data_ra(env, src + i, ra);
-x |= cpu_ldub_data_ra(env, dest + i, ra);
+/* OC always processes one more byte than specified - maximum is 256 */
+l++;
+
+srca1 = access_prepare(env, src, l, MMU_DATA_LOAD, ra);
+srca2 = access_prepare(env, dest, l, MMU_DATA_LOAD, ra);
+desta = access_prepare(env, dest, l, MMU_DATA_STORE, ra);
+for (i = 0; i < l; i++) {
+const uint8_t x = access_get_byte(env, &srca1, i, ra) |
+  access_get_byte(env, &srca2, i, ra);
+
 c |= x;
-cpu_stb_data_ra(env, dest + i, x, ra);
+access_set_byte(env, &desta, i, x, ra);
 }
 return c != 0;
 }
-- 
2.21.0