2011/9/26 Lluís Vilanova <vilan...@ac.upc.edu>: > Stefan Hajnoczi writes: > >> On Mon, Sep 26, 2011 at 12:23:21AM +0200, Lluís Vilanova wrote: >>> 1) Cannot start QEMU with KVM when the device is enabled: >>> kvm_set_phys_mem: error registering slot: Invalid argument >>> >>> 2) The driver never gets called on a read/write to its memory > >> If I add #include "pci.h" at the top of the file, change >> TARGET_PAGE_SIZE to 4096 (generic device code is not supposed to be >> target-dependent), and throw foo.o into Makefile.objs it builds here. > >> It launches successfully with -enable-kvm and I can see the device >> inside a VM. My qemu.git/HEAD is >> 1ce9ce6a6184f0192015ba9adf1123d89cd47a7b. > > Well, my intent is to implement the backdoor communication channel I rambled > about some time ago. Now, instead of overloading some unused opcodes, I use a > virtual device that is target agnostic (as someone wisely suggested). > > As the device is mmap'ed into userspace to interact with it, I thought it made > sense to use TARGET_PAGE_SIZE to establish the device's mappable ranges. > > Note that the device is not compiled with all the libhw code, so > TARGET_PAGE_SIZE is not poisoned. > > In any case, now I've just seen that the code I sent does indeed (almost) > work... the offending code is in the part I did not send. The second bar uses > a > simple malloc'ed piece of data that the user can use as a scratchpad for the > communication with QEMU, so that the flow is: > > - guest writes data into data channel > - guest writes anything into the control channel > - do in QEMU whatever is encoded in the data channel > > It is the second bar that generates the problems with KVM: It can work in my env with the codes below, and i can see the device. But it is pity that i don't know to test the two bar.
> > s->data_ptr = g_malloc(s->size); > memory_region_init_ram_ptr(&s->data, &s->dev.qdev, "backdoor.data", > s->size, s->data_ptr); > pci_register_bar(&s->dev, 1, PCI_BASE_ADDRESS_SPACE_MEMORY, &s->data); > > >> I only had a few minutes and couldn't test reading from BAR0, but you >> might want to get 32-bit reads working first before trying 64-bit. > > The next problem is using 64bit reads and writes... if I set min_access_size > and > max_access_size to 4, I get the calls to 'control_io_read', but not with 8... > > I've attached the real code I'm using, just to make it easier to test. > > > Thanks a lot, > Lluis > > -- > "And it's much the same thing with knowledge, for whenever you learn > something new, the whole world becomes that much richer." > -- The Princess of Pure Reason, as told by Norton Juster in The Phantom > Tollbooth > > -- Regards, Zhi Yong Wu
