how emulated disk IO translated to physical disk IO on host side

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Hi all,

i am trying to figure out the code path which translate the emulated
disk IO issued by VM to actual physical disk IO on host side. Can
anyone give me a clear view about this?

i read the kvm side code about the VMexit handling, the handle_io()
will be called for IO exits. for IO job that cannot be handled inside
the hyperviser, it will switch to qemu-kvm process and the handle_io()
at qemu side will be called. finally it seems invoke the
ioport_read()/ioport_write() which invoke the actual registered
read/write operator. Then i get lost here, i do not know for emulated
disk io which function will be responsible for the remaining job. i.e.
catch the cmd for accessing the virtual disk and translate to the
read/write to offset of the disk img file (assume we use file for
virtual disk), and then issue the system call to the host to issue the
real io cmd to physical disk.

i really hope someone can help me with it. if my understanding is not
correct, please figure out. i will be appreciated.

Thanks,
Sheng
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