Re: [Qemu-devel] [PATCH 3/3] ide: really restart pending and in-flight atapi dma

[Pavel Butsykin <pbutsykin@virtuozzo.com>]

On 23.03.2016 22:36, John Snow wrote:
>
>
> On 03/23/2016 06:26 AM, Denis V. Lunev wrote:
>> From: Pavel Butsykin <pbutsykin@virtuozzo.com>
>>
>> Restart of ATAPI DMA used to be unreachable, because the request to do
>> so wasn't indicated in bus->error_status due to the lack of spare bits, and
>> ide_restart_bh() would return early doing nothing.
>>
>> This patch makes use of the observation that not all bit combinations were
>> possible in ->error_status. In particular, IDE_RETRY_READ only made sense
>> together with IDE_RETRY_DMA or IDE_RETRY_PIO. This allows to re-use
>> IDE_RETRY_READ alone as an indicator of ATAPI DMA restart request.
>>
>> As a means against confusion, macros are added to test the state of
>> ->error_status.
>>
>> The patch fixes the restart of both in-flight and pending ATAPI DMA,
>> following the scheme similar to that of IDE DMA.
>>
>> Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
>> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> CC: John Snow <jsnow@redhat.com>
>> ---
>>   hw/ide/atapi.c    | 15 +++++++--------
>>   hw/ide/core.c     | 23 ++++++++++-------------
>>   hw/ide/internal.h | 18 ++++++++++++++++++
>>   3 files changed, 35 insertions(+), 21 deletions(-)
>>
>> diff --git a/hw/ide/atapi.c b/hw/ide/atapi.c
>> index 8816b38..0d51b44 100644
>> --- a/hw/ide/atapi.c
>> +++ b/hw/ide/atapi.c
>> @@ -375,22 +375,25 @@ static void ide_atapi_cmd_check_status(IDEState *s)
>>   }
>>   /* ATAPI DMA support */
>>
>> -/* XXX: handle read errors */
>>   static void ide_atapi_cmd_read_dma_cb(void *opaque, int ret)
>>   {
>>       IDEState *s = opaque;
>>       int data_offset, n;
>>
>> -    if (ret < 0) { /* XXX: handle -ESTATESAVE for migration */
>> +    if (ret < 0) {
>>           if (ret == -ESTATESAVE) {
>>               /*
>>                * This case is not really an error
>>                * but a request to save the state.
>>                */
>> +            s->bus->error_status = IDE_RETRY_ATAPI;
>>               return;
>> +        } else if (ide_handle_rw_error(s, -ret, IDE_RETRY_ATAPI)) {
>> +            if (s->bus->error_status) {
>> +                return;
>> +            }
>> +            goto eot;
>>           }
>> -        ide_atapi_io_error(s, ret);
>> -        goto eot;
>>       }
>>
>>       if (s->io_buffer_size > 0) {
>> @@ -488,10 +491,6 @@ static void ide_atapi_cmd_read(IDEState *s, int lba, int nb_sectors,
>>       }
>>   }
>>
>> -
>> -/* Called by *_restart_bh when the transfer function points
>> - * to ide_atapi_cmd
>> - */
>>   void ide_atapi_dma_restart(IDEState *s)
>>   {
>>       /*
>> diff --git a/hw/ide/core.c b/hw/ide/core.c
>> index 872e11f..6d7533f 100644
>> --- a/hw/ide/core.c
>> +++ b/hw/ide/core.c
>> @@ -56,7 +56,6 @@ static const int smart_attributes[][12] = {
>>       { 190,  0x03, 0x00, 0x45, 0x45, 0x1f, 0x00, 0x1f, 0x1f, 0x00, 0x00, 0x32},
>>   };
>>
>> -static int ide_handle_rw_error(IDEState *s, int error, int op);
>>   static void ide_dummy_transfer_stop(IDEState *s);
>>
>>   static void padstr(char *str, const char *src, int len)
>> @@ -772,7 +771,7 @@ void ide_dma_error(IDEState *s)
>>       ide_set_irq(s->bus);
>>   }
>>
>> -static int ide_handle_rw_error(IDEState *s, int error, int op)
>> +int ide_handle_rw_error(IDEState *s, int error, int op)
>>   {
>>       bool is_read = (op & IDE_RETRY_READ) != 0;
>>       BlockErrorAction action = blk_get_error_action(s->blk, is_read, error);
>> @@ -782,8 +781,10 @@ static int ide_handle_rw_error(IDEState *s, int error, int op)
>>           s->bus->error_status = op;
>>       } else if (action == BLOCK_ERROR_ACTION_REPORT) {
>>           block_acct_failed(blk_get_stats(s->blk), &s->acct);
>> -        if (op & IDE_RETRY_DMA) {
>> +        if (IS_IDE_RETRY_DMA(op)) {
>>               ide_dma_error(s);
>> +        } else if (IS_IDE_RETRY_ATAPI(op)) {
>> +            ide_atapi_io_error(s, -error);
>>           } else {
>>               ide_rw_error(s);
>>           }
>> @@ -2533,13 +2534,13 @@ static void ide_restart_bh(void *opaque)
>>           }
>>       }
>>
>> -    if (error_status & IDE_RETRY_DMA) {
>> +    if (IS_IDE_RETRY_DMA(error_status)) {
>>           if (error_status & IDE_RETRY_TRIM) {
>>               ide_restart_dma(s, IDE_DMA_TRIM);
>>           } else {
>>               ide_restart_dma(s, is_read ? IDE_DMA_READ : IDE_DMA_WRITE);
>>           }
>> -    } else if (error_status & IDE_RETRY_PIO) {
>> +    } else if (IS_IDE_RETRY_PIO(error_status)) {
>>           if (is_read) {
>>               ide_sector_read(s);
>>           } else {
>> @@ -2547,15 +2548,11 @@ static void ide_restart_bh(void *opaque)
>>           }
>>       } else if (error_status & IDE_RETRY_FLUSH) {
>>           ide_flush_cache(s);
>> +    } else if (IS_IDE_RETRY_ATAPI(error_status)) {
>> +        assert(s->end_transfer_func == ide_atapi_cmd);
>> +        ide_atapi_dma_restart(s);
>>       } else {
>> -        /*
>> -         * We've not got any bits to tell us about ATAPI - but
>> -         * we do have the end_transfer_func that tells us what
>> -         * we're trying to do.
>> -         */
>> -        if (s->end_transfer_func == ide_atapi_cmd) {
>> -            ide_atapi_dma_restart(s);
>> -        }
>> +        abort();
>>       }
>>   }
>>
>> diff --git a/hw/ide/internal.h b/hw/ide/internal.h
>> index dcd8627..2e845d0 100644
>> --- a/hw/ide/internal.h
>> +++ b/hw/ide/internal.h
>> @@ -508,11 +508,27 @@ struct IDEDevice {
>>   /* These are used for the error_status field of IDEBus */
>>   #define IDE_RETRY_DMA  0x08
>>   #define IDE_RETRY_PIO  0x10
>> +#define IDE_RETRY_ATAPI 0x20 /* reused IDE_RETRY_READ bit */
>>   #define IDE_RETRY_READ  0x20
>>   #define IDE_RETRY_FLUSH 0x40
>>   #define IDE_RETRY_TRIM 0x80
>>   #define IDE_RETRY_HBA  0x100
>>
>> +#define IS_IDE_RETRY_DMA(_status) \
>> +    ((_status) & IDE_RETRY_DMA)
>> +
>> +#define IS_IDE_RETRY_PIO(_status) \
>> +    ((_status) & IDE_RETRY_PIO)
>> +
>> +/*
>> + * The method of the IDE_RETRY_ATAPI determination is to use a previously
>> + * impossible bit combination as a new status value.
>> + */
>> +#define IS_IDE_RETRY_ATAPI(_status)   \
>> +    (((_status) & IDE_RETRY_ATAPI) && \
>> +     !IS_IDE_RETRY_DMA(_status) &&    \
>> +     !IS_IDE_RETRY_PIO(_status))
>> +
>>   /*
>>    * a code to trigger entering error path and save/restore the "ready to DMA"
>>    * state just like DMA-ing state. (Ab)use EINPROGRESS as it's not supposed to
>> @@ -604,4 +620,6 @@ void ide_bus_new(IDEBus *idebus, size_t idebus_size, DeviceState *dev,
>>                    int bus_id, int max_units);
>>   IDEDevice *ide_create_drive(IDEBus *bus, int unit, DriveInfo *drive);
>>
>> +int ide_handle_rw_error(IDEState *s, int error, int op);
>> +
>>   #endif /* HW_IDE_INTERNAL_H */
>>
>
> Sorry, this causes "make check" to fail on the AHCI test.
>
> Try this:
>
> export QTEST_QEMU_BINARY ./x86_64-softmmu/qemu-system-x86_64
> make tests/ahci-test
> ./tests/ahci-test -p /x86_64/ahci/io/ncq/retry
>
> The QEMU instance aborts in hw/ide/core.c line 2555,
> function 'ide_restart_bh'
>
>      } else {
>          abort(); <-- here.
>      }
>
>
Thank you, it seems that I have missed the case for the IDE_RETRY_HBA.

     /* The HBA has generically asked to be kicked on retry */
     if (error_status & IDE_RETRY_HBA) {
         if (s->bus->dma->ops->restart) {
             s->bus->dma->ops->restart(s->bus->dma);
         }
     }
This case uses only to the AHCI. Why are we after the processing of
the IDE_RETRY_HBA case still need to handle other IDE_RETRY_* cases?
It seems that here we just need to get out from the ide_restart_bh function.