Re: [PATCH v5 3/3] hw/uefi/ovmf-log: add maxsize parameter

[Markus Armbruster <armbru@redhat.com>]

Gerd Hoffmann <kraxel@redhat.com> writes:

> Allow limiting the amount of log output sent.  Allow up to 1 MiB.
> In case the guest log buffer is larger than 1 MiB limit the output
> instead of throwing an error.
>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  hw/uefi/ovmf-log.c   | 42 ++++++++++++++++++++++++++++++++++--------
>  hmp-commands-info.hx |  4 ++--
>  qapi/machine.json    |  5 +++++
>  3 files changed, 41 insertions(+), 10 deletions(-)
>
> diff --git a/hw/uefi/ovmf-log.c b/hw/uefi/ovmf-log.c
> index e281a980a101..28788620e3f6 100644
> --- a/hw/uefi/ovmf-log.c
> +++ b/hw/uefi/ovmf-log.c
> @@ -18,6 +18,7 @@
>  #include "qapi/error.h"
>  #include "qapi/type-helpers.h"
>  #include "qapi/qapi-commands-machine.h"
> +#include "qobject/qdict.h"
>  
>  
>  /* ----------------------------------------------------------------------- */
> @@ -164,7 +165,8 @@ static void handle_ovmf_log_range(GString *out,
>      }
>  }
>  
> -FirmwareLog *qmp_query_firmware_log(Error **errp)
> +FirmwareLog *qmp_query_firmware_log(bool have_max_size, uint64_t max_size,
> +                                    Error **errp)
>  {
>      MEM_DEBUG_LOG_HDR header;
>      dma_addr_t offset, base;
> @@ -184,18 +186,40 @@ FirmwareLog *qmp_query_firmware_log(Error **errp)
>          return NULL;
>      }
>  
> -    if (header.DebugLogSize > MiB) {
> -        /* default size is 128k (32 pages), allow up to 1M */
> -        error_setg(errp, "firmware log: log buffer is too big");
> -        return NULL;
> -    }
> -
>      if (header.DebugLogHeadOffset > header.DebugLogSize ||
>          header.DebugLogTailOffset > header.DebugLogSize) {
>          error_setg(errp, "firmware log: invalid header");
>          return NULL;
>      }
>  
> +    if (have_max_size) {
> +        if (max_size > MiB) {
> +            error_setg(errp, "firmware log: max-size larger than 1 MiB");

"parameter 'max-size' exceeds 1MiB" or similar.

> +            return NULL;
> +        }
> +    } else {
> +        max_size = MiB;
> +    }
> +
> +    /* adjust header.DebugLogHeadOffset so we return at most maxsize bytes */
> +    if (header.DebugLogHeadOffset > header.DebugLogTailOffset) {
> +        /* wrap around */
> +        if (header.DebugLogTailOffset > max_size) {
> +            header.DebugLogHeadOffset = header.DebugLogTailOffset - max_size;
> +        } else {
> +            uint64_t max_chunk = max_size - header.DebugLogTailOffset;
> +            if (header.DebugLogSize > max_chunk &&
> +                header.DebugLogHeadOffset < header.DebugLogSize - max_chunk) {
> +                header.DebugLogHeadOffset = header.DebugLogSize - max_chunk;
> +            }
> +        }
> +    } else {
> +        if (header.DebugLogTailOffset > max_size &&
> +            header.DebugLogHeadOffset < header.DebugLogTailOffset - max_size) {
> +            header.DebugLogHeadOffset = header.DebugLogTailOffset - max_size;
> +        }
> +    }

Didn't review this part; my brain's fried for today :)

> +
>      base = offset + header.HeaderSize;
>      if (header.DebugLogHeadOffset > header.DebugLogTailOffset) {
>          /* wrap around */
> @@ -239,8 +263,10 @@ void hmp_info_firmware_log(Monitor *mon, const QDict *qdict)
>      Error *err = NULL;
>      FirmwareLog *log;
>      gsize log_len;
> +    int64_t maxsize;
>  
> -    log = qmp_query_firmware_log(&err);
> +    maxsize = qdict_get_try_int(qdict, "maxsize", -1);
> +    log = qmp_query_firmware_log(maxsize != -1, (uint64_t)maxsize, &err);
>      if (err)  {
>          hmp_handle_error(mon, err);
>          return;
> diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
> index f0aef419923c..f00d7081b40c 100644
> --- a/hmp-commands-info.hx
> +++ b/hmp-commands-info.hx
> @@ -993,8 +993,8 @@ ERST
>  
>      {
>          .name       = "firmware-log",
> -        .args_type  = "",
> -        .params     = "",
> +        .args_type  = "maxsize:o?",
> +        .params     = "[maxsize]",
>          .help       = "show the firmware (ovmf) debug log",
>          .cmd        = hmp_info_firmware_log,
>      },

Might want to spell it max-size for consistency with QMP.  Up to you.

> diff --git a/qapi/machine.json b/qapi/machine.json
> index 96133e5c71cf..e4b15680c172 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -1858,9 +1858,14 @@
>  #
>  # Find firmware memory log buffer in guest memory, return content.
>  #
> +# @max-size: limit the amount of log data returned.  Up to 1 MiB if
> +#            log data is allowed.  In case the amout of log data is

What are you trying to convey by "if log data is allowed"?

s/amout/amount/

> +#            larger than max-size the tail of the log is returned.

Please use @max-size here for nicer rendering.

> +#
>  # Since: 10.2
>  ##
>  { 'command': 'query-firmware-log',
> +  'data': { '*max-size': 'size' },
>    'returns': 'FirmwareLog' }
>  
>  ##