vitalif
commented
2 years ago Hi, that's something interesting. Are these read or write requests? What's the idea of sharing the same address? I.e. as I understand if it requests to read 2 different parts of data into the same buffer it can't rely on anything? I.e. the real hardware also doesn't guarantee any order as I understand. Or are these write requests? But as I understand if these shared requests were write requests they would be executed correctly?..
mirrorll
hi, @vitalif i use windows 10 as guest os and found that when it start， some of the qemu iov array item use the same address at a IO request。for example in a iovcnt = 5 request，iov[0] and iov[3] use the same address。when client slice the reqeust (in two part_op), part_op[0] use iov[0]-iov[2] and send to one osd , part_op[1] use iov[3]-iov[4] and send to another osd. if part_op[1] return earlier than part_op[0], the address of iov[0] and iov[3] will use the data of iov[0], this result is not same as use qcow2 file as vm disk. so, when the request opcode is read, i use another malloc part_op iov buf to save the data read from different osd, and memcpy data to qemu iov after all part_op done. but when i calc crc32 at part_op iov and qemu iov, some time it is different。i mprotect the qemu iov PROT_READ before all part_op done. then mprotect it PROT_READ|PROT_WRITE. but this way will cause qemu error: kvm run failed Bad address.