Re: [Qemu-devel] [PATCH v3 16/16] [RFC] dma/rc4030: do multiple calls to address_space_rw when doing DMA transfers

["Hervé Poussineau" <hpoussin@reactos.org>]

Hi Leon,

Le 10/06/2015 14:00, Leon Alrae a écrit :
> Hi Hervé,
>
> On 03/06/2015 21:45, Hervé Poussineau wrote:
>> This fixes Windows NT 4.0/MIPS, which was always bugchecking with
>> IRQL_NOT_LESS_OR_EQUAL.
>>
>> Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
>> ---
>>   hw/dma/rc4030.c | 14 ++++++++++++--
>>   1 file changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/dma/rc4030.c b/hw/dma/rc4030.c
>> index 3efa6de..deac0a8 100644
>> --- a/hw/dma/rc4030.c
>> +++ b/hw/dma/rc4030.c
>> @@ -681,6 +681,7 @@ static void rc4030_do_dma(void *opaque, int n, uint8_t *buf, int len, int is_wri
>>       rc4030State *s = opaque;
>>       hwaddr dma_addr;
>>       int dev_to_mem;
>> +    int i;
>>
>>       s->dma_regs[n][DMA_REG_ENABLE] &= ~(DMA_FLAG_TC_INTR | DMA_FLAG_MEM_INTR | DMA_FLAG_ADDR_INTR);
>>
>> @@ -699,8 +700,17 @@ static void rc4030_do_dma(void *opaque, int n, uint8_t *buf, int len, int is_wri
>>       dma_addr = s->dma_regs[n][DMA_REG_ADDRESS];
>>
>>       /* Read/write data at right place */
>> -    address_space_rw(&s->dma_as, dma_addr, MEMTXATTRS_UNSPECIFIED,
>> -                     buf, len, is_write);
>> +    for (i = 0; i < len; ) {
>> +        int ncpy = DMA_PAGESIZE - (dma_addr & (DMA_PAGESIZE - 1));
>> +        if (ncpy > len - i) {
>> +            ncpy = len - i;
>> +        }
>> +        address_space_rw(&s->dma_as, dma_addr, MEMTXATTRS_UNSPECIFIED,
>> +                         buf + i, ncpy, is_write);
>> +
>> +        dma_addr += ncpy;
>> +        i += ncpy;
>> +    }
>>
>>       s->dma_regs[n][DMA_REG_ENABLE] |= DMA_FLAG_TC_INTR;
>>       s->dma_regs[n][DMA_REG_COUNT] -= len;
>>
>
> I'm sending out current target-mips queue soon and I can include this series,
> but I'm not quite sure what to do with this RFC patch. I presume you put RFC
> here because it's a workaround for a bug, but it's not clear where the actual
> bug is?

Indeed, that's a workaround for a bug that I failed to identify. You can still take the RFC patch as a patch, as I didn't see any objection (yet).
I think we can defer the bug correction for later.

Regards,

Hervé