Re: [PATCH 2/6] dump/win_dump: Improve error messages on write error

[Markus Armbruster <armbru@redhat.com>]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> On 13/5/24 16:16, Markus Armbruster wrote:
>> create_win_dump() and write_run report qemu_write_full() failure to
>> their callers as
>>      An IO error has occurred
>> The errno set by qemu_write_full() is lost.
>> Improve this to
>>      win-dump: failed to write header: <description of errno>
>> and
>>      win-dump: failed to save memory: <description of errno>
>> This matches how dump.c reports similar errors.
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> ---
>>   dump/win_dump.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>> diff --git a/dump/win_dump.c b/dump/win_dump.c
>> index b7bfaff379..0e4fe692ce 100644
>> --- a/dump/win_dump.c
>> +++ b/dump/win_dump.c
>> @@ -12,7 +12,6 @@
>>   #include "sysemu/dump.h"
>>   #include "qapi/error.h"
>>   #include "qemu/error-report.h"
>> -#include "qapi/qmp/qerror.h"
>>   #include "exec/cpu-defs.h"
>>   #include "hw/core/cpu.h"
>>   #include "qemu/win_dump_defs.h"
>> @@ -52,6 +51,7 @@ static size_t write_run(uint64_t base_page, uint64_t page_count,
>>       uint64_t addr = base_page << TARGET_PAGE_BITS;
>>       uint64_t size = page_count << TARGET_PAGE_BITS;
>>       uint64_t len, l;
>> +    int eno;
>>       size_t total = 0;
>>         while (size) {
>> @@ -65,9 +65,10 @@ static size_t write_run(uint64_t base_page, uint64_t page_count,
>>           }
>>             l = qemu_write_full(fd, buf, len);
>> +        eno = errno;
>
> Hmm this show the qemu_write_full() API isn't ideal.
> Maybe we could pass &l as argument and return errno.
> There are only 20 calls.

qemu_write_full() is a drop-in replacement for write().

>>           cpu_physical_memory_unmap(buf, addr, false, len);
>>           if (l != len) {
>> -            error_setg(errp, QERR_IO_ERROR);
>> +            error_setg_errno(errp, eno, "win-dump: failed to save memory");
>>               return 0;
>>           }
>>   @@ -459,7 +460,7 @@ void create_win_dump(DumpState *s, Error **errp)
>>         s->written_size = qemu_write_full(s->fd, h, hdr_size);
>>       if (s->written_size != hdr_size) {
>> -        error_setg(errp, QERR_IO_ERROR);
>> +        error_setg_errno(errp, errno, "win-dump: failed to write header");
>>           goto out_restore;
>>       }
>>