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[Qemu-devel] [Xen-devel] [Block dev] : Qemu block ide_dma_read call rout
From: |
Shailesh Kumar |
Subject: |
[Qemu-devel] [Xen-devel] [Block dev] : Qemu block ide_dma_read call routine |
Date: |
Tue, 10 Feb 2015 19:51:05 -0800 |
Hi,
I am implementing read equivalent routine in qemu. Can some one
help me understand control flow of the qemu read/write
implementation.
I am using xen-4.2.0 and qemu-1.6.1
My requirement is simple:
I have a 1024*1024 buffer already filled with some useful data.
Now when windows (my guest OS) does IDE_DMA_READ command to the disk,
I want to intercept it and fill data from my private buffer.
my intention is to leverage existing dma_read infrastructure and
overwrite the read buffer-data at the lowest level of qemu . That way
the buffers /vectors "qiov" which are prepared due to cmd IDE_DMA_READ
will copy and return data from my data-buffer to guest-OS.
I could trace the control from.
ide_sector_start_dma
-> s->bus->dma->ops->start_dma
-> ide_dma_cb
->dma_bdrv_read
-> bdrv_aio_readv
. ->bdrv_co_aio_rw_vector
-> bdrv_co_do_rw "coroutine"
-> bdrv_co_do_readv
-> drv->bdrv_co_readv (( in my case it is
from raw.c raw_co_readv ))
-> bdrv_co_readv
-> bdrv_co_do_readv
->in bdrv_co_do_rw the bottom half is scheduled
bdrv_co_em_bh -->> this will invoke -> ide_dma_cb () which is
again the starting point. Looks like there a double-linked list
maintained for the coroutine entries and are off loaded to qemu-wait
queue during this process.
Now I need help to understand where to look for to find the last
read/write system call which will get the data out from the disk for
guest-OS (windows) .
I am seeking suggestions and help for the same.
thanks
S. Kumar
- [Qemu-devel] [Xen-devel] [Block dev] : Qemu block ide_dma_read call routine,
Shailesh Kumar <=