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[PATCH-for-10.0,3/3] hw/char/riscv_htif: Clarify MemoryRegionOps expect 32-bit accesses

Message ID 20241129154304.34946-4-philmd@linaro.org
State New
Headers show
Series hw/char/riscv_htif: Remove tswap64() calls | expand

Commit Message

Philippe Mathieu-Daudé Nov. 29, 2024, 3:43 p.m. UTC
Looking at htif_mm_ops[] read/write handlers, we notice they
expect 32-bit values to accumulate into to the 'fromhost' and
'tohost' 64-bit variables. Explicit by setting the .impl
min/max fields.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
Notes

1/ these variables belong to HTIFState but are declared statically!

  static uint64_t fromhost_addr, tohost_addr, begin_sig_addr, end_sig_addr;

2/ I believe a 64-bit implementation would simplify the logic.

3/ This is a non-QOM device model!

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/char/riscv_htif.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Daniel Henrique Barboza Nov. 29, 2024, 5:08 p.m. UTC | #1
On 11/29/24 12:43 PM, Philippe Mathieu-Daudé wrote:
> Looking at htif_mm_ops[] read/write handlers, we notice they
> expect 32-bit values to accumulate into to the 'fromhost' and
> 'tohost' 64-bit variables. Explicit by setting the .impl
> min/max fields.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> Notes
> 
> 1/ these variables belong to HTIFState but are declared statically!
> 
>    static uint64_t fromhost_addr, tohost_addr, begin_sig_addr, end_sig_addr;
> 
> 2/ I believe a 64-bit implementation would simplify the logic.


Perhaps. We would need to check with the protocol first. There might be
a reason why we're using 64 bit read/writes internally while doing 32 bits
r/w in the device.


For now:

Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

> 
> 3/ This is a non-QOM device model!
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   hw/char/riscv_htif.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/hw/char/riscv_htif.c b/hw/char/riscv_htif.c
> index 3f84d8d6738..db69b5e3ca7 100644
> --- a/hw/char/riscv_htif.c
> +++ b/hw/char/riscv_htif.c
> @@ -325,6 +325,10 @@ static const MemoryRegionOps htif_mm_ops = {
>       .read = htif_mm_read,
>       .write = htif_mm_write,
>       .endianness = DEVICE_LITTLE_ENDIAN,
> +    .impl = {
> +        .min_access_size = 4,
> +        .max_access_size = 4,
> +    },
>   };
>   
>   HTIFState *htif_mm_init(MemoryRegion *address_space, Chardev *chr,
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Patch

diff --git a/hw/char/riscv_htif.c b/hw/char/riscv_htif.c
index 3f84d8d6738..db69b5e3ca7 100644
--- a/hw/char/riscv_htif.c
+++ b/hw/char/riscv_htif.c
@@ -325,6 +325,10 @@  static const MemoryRegionOps htif_mm_ops = {
     .read = htif_mm_read,
     .write = htif_mm_write,
     .endianness = DEVICE_LITTLE_ENDIAN,
+    .impl = {
+        .min_access_size = 4,
+        .max_access_size = 4,
+    },
 };
 
 HTIFState *htif_mm_init(MemoryRegion *address_space, Chardev *chr,