/srv/irclogs.linaro.org/2018/01/22/#kvm-arm.txt

mazbielski: do you actually give this memory to the guest as a memslot?08:25
bielskimaz: I guess QEMU does by a bit customized backend, but I am actually chasing it now how it works08:29
mazbielski: the fault you describe can only occur when you don't have read permission on the memory, which is pretty unexpected. this makes me think that you're not mapping the memory correctly.08:43
bielskiif that would help, it works in TCG mode08:44
bielskibut simply this is not my interest, I want a VM08:44
mazbielski: TCG mode with KVM in TCG? or just the guest running in TCG?08:46
bielskithe second, when I run my system without KVM the mmap'ed /dev/mem RAM works fine, just obviously slow08:47
bielskibut when adding '-enable kvm' it crashes at the first instruction (PC=0x40000000) and the host console prints 'Unexpected L2 read permission error'08:49
bielskiwhich somehow corresponds to what you are saying, question why...08:49
mazbecause there is no reason why you should be able to access to that physical memory from a guest unless you actually map it into the guest. the whole purpose of a hypervisor is to isolate the guest from the physical resources...08:56
mazor am I missing what you try to do?08:57
mazwhat is at that address? is that memory provided by QEMU to the guest? or something else?08:58
mazif it is "something else", then the guest won't be able to access it unless you tell KVM about it.08:59
=== agraf` is now known as agraf
bielskimaz: you may be totally right, I just need a way to tell the hypervisor that this is a valid piece of guest's memory16:49
chazybielski: then you need to use KVM_SET_USER_MEMORY_REGION.16:57
pm215well, ideally you want to tell qemu to do things so it uses KVM_SET_USER_MEMORY_REGION...17:15
chazyI thought it was doing something without QEMU, but I may have misunderstood.17:38
chazy(clarification: I thougth bielski was doing something with his own userspace tool, not QEMU)17:39
bielskiit is with QEMU, I simply thought that if in TCG mode it is enough that the RAM backend is just properly initialized, then it will be samely in KVM17:43
bielskibut from you are suggesting I should also setup hypervisor additionally with this backend resources17:44
bielskiI'll give this approach a shot, thx17:44
pm215bielski: QEMU already has code to call KVM_SET_USER_MEMORY_REGION for ram17:45
pm215if your setup is not causing that machinery to be invoked, you should find out why not, rather than reimplementing a bunch of code17:45
bielskipm215: Yes I have captured that in kvm-all.c and further down the call stack. Actually I am trying to find out why it is not setup properly.18:09

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