Hi ----- Original Message ----- > Hello! > > I have merged this PULL into our local repository and my colleague gave it a > try. > It seems to work, but looks like ivshmem + memdev + hugetlbfs doesn't do the > right thing. Memdev does attach itself to a hugetlb, but we cannot actually > share data with it. > Our command line was: > --- cut --- > /usr/local/bin/qemu-system-aarch64 \ > -name ivshmem1_huge \ > -machine virt,accel=kvm,usb=off,gic-version=3 \ > -cpu host -m 2048 \ > -realtime mlock=off \ > -smp 8,sockets=8,cores=1,threads=1 \ > -nographic \ > -kernel /var/lib/libvirt/images/Image_uio \ > -append console='ttyAMA0,115200n8 root=/dev/sda4 rootwait > hugepages=128 earlycon=pl011,0x9000000' \ > -device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x1 \ > -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x1 \ > -device virtio-scsi-pci,id=scsi0,bus=pci.2,addr=0x1 \ > -drive > > file=/var/lib/libvirt/images/sda3_pool/ivshmem1_huge.qcow2,if=none,id=drive-scsi0-0-0-0,format=qcow2 > \ > -device > > scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=1 > \ > -object > memory-backend-file,size=4G,mem-path=/dev/huge,id=mb1,share=on \ > -device ivshmem,memdev=mb1 \ > -msg timestamp=on > --- cut --- > > The problem is that memdev creates a file as temporary, and then immediately > unlinks it. Therefore, we cannot feed the same file to another VM. These > are open files, used by two running VMs, which are supposed to exchange > data via ivshmem. > --- cut --- > [root@thunderx-2 igor]# ls -l /proc/34845/fd > total 0 > lrwx------ 1 root root 64 Oct 9 06:59 0 -> /dev/pts/2 > lrwx------ 1 root root 64 Oct 9 06:59 1 -> /dev/pts/2 > ... > lrwx------ 1 root root 64 Oct 9 06:59 7 -> anon_inode:[eventfd] > lrwx------ 1 root root 64 Oct 9 06:59 8 -> > /dev/huge/qemu_back_mem._objects_mb1.lwEeDc (deleted) > lrwx------ 1 root root 64 Oct 9 06:59 9 -> /dev/kvm > [root@thunderx-2 igor]# ls -l /proc/34866/fd > total 0 > lrwx------ 1 root root 64 Oct 9 06:59 0 -> /dev/pts/0 > lrwx------ 1 root root 64 Oct 9 06:59 1 -> /dev/pts/0 > ... > lrwx------ 1 root root 64 Oct 9 06:59 7 -> anon_inode:[eventfd] > lrwx------ 1 root root 64 Oct 9 06:59 8 -> > /dev/huge/qemu_back_mem._objects_mb1.0Myp8M (deleted) > lrwx------ 1 root root 64 Oct 9 06:59 9 -> /dev/kvm > --- cut --- > Due to the same reason, we cannot also exchange data between host and VM. > Is it a flaw or do we just do something wrong?
file_ram_alloc() only allocates with temporary files, even when using share=true. We could teach it to use an existing file instead. This is an additional feature that could be considered after this series, since it's not a regression. Also, the prefered way to share memory (including hugetlb) is to use the ivshmem-server (that way you have a clear owner, and you can signal vm2vm). > Tested-by: Igor Skalkin <i.skal...@samsung.com> Thanks a lot for testing. > > Kind regards, > Pavel Fedin > Expert Engineer > Samsung Electronics Research center Russia > > >
