Re: [PATCH 5/7] hw/hyperv/syndbg: common compilation unit

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 6/3/25 17:23, Pierrick Bouvier wrote:
> On 3/6/25 08:19, Richard Henderson wrote:
>> On 3/5/25 22:41, Pierrick Bouvier wrote:
>>> Replace TARGET_PAGE.* by runtime calls
>>>
>>> Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
>>> ---
>>>    hw/hyperv/syndbg.c    | 7 ++++---
>>>    hw/hyperv/meson.build | 2 +-
>>>    2 files changed, 5 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/hw/hyperv/syndbg.c b/hw/hyperv/syndbg.c
>>> index d3e39170772..f9382202ed3 100644
>>> --- a/hw/hyperv/syndbg.c
>>> +++ b/hw/hyperv/syndbg.c
>>> @@ -14,7 +14,7 @@
>>>    #include "migration/vmstate.h"
>>>    #include "hw/qdev-properties.h"
>>>    #include "hw/loader.h"
>>> -#include "cpu.h"
>>> +#include "exec/target_page.h"
>>>    #include "hw/hyperv/hyperv.h"
>>>    #include "hw/hyperv/vmbus-bridge.h"
>>>    #include "hw/hyperv/hyperv-proto.h"
>>> @@ -188,7 +188,8 @@ static uint16_t handle_recv_msg(HvSynDbg *syndbg, 
>>> uint64_t outgpa,
>>>                                    uint64_t timeout, uint32_t 
>>> *retrieved_count)
>>>    {
>>>        uint16_t ret;
>>> -    uint8_t data_buf[TARGET_PAGE_SIZE - UDP_PKT_HEADER_SIZE];
>>> +    const size_t buf_size = qemu_target_page_size() - 
>>> UDP_PKT_HEADER_SIZE;
>>> +    uint8_t *data_buf = g_alloca(buf_size);
>>>        hwaddr out_len;
>>>        void *out_data;
>>>        ssize_t recv_byte_count;
>>
>> We've purged the code base of VLAs, and those are preferable to alloca.
>> Just use g_malloc and g_autofree.
>>
> 
> I hesitated, due to potential performance considerations for people 
> reviewing the patch. I'll switch to heap based storage.

OTOH hyperv is x86-only, so we could do:

#define BUFSZ (4 * KiB)

handle_recv_msg()
{
   uint8_t data_buf[BUFSZ - UDP_PKT_HEADER_SIZE];
   ...

hv_syndbg_class_init()
{
   assert(BUFSZ > qemu_target_page_size());
   ...

and call it a day.