On Tue, Mar 15, 2022 at 5:47 PM Ralf Ramsauer <ralf.ramsa...@oth-regensburg.de> wrote: > > > > On 15/03/2022 09:33, Anup Patel wrote: > > On Tue, Mar 15, 2022 at 12:18 PM Alistair Francis <alistai...@gmail.com> > > wrote: > >> > >> On Sun, Mar 13, 2022 at 12:12 PM Ralf Ramsauer > >> <ralf.ramsa...@oth-regensburg.de> wrote: > >>> > >>> Hi, > >>> > >>> I'm trying to run Linux/QEMU+KVM inside an emulated > >>> qemu-system-riscv64 VM (x86 host). On latest&greatest QEMU (1416688c53), > >>> I run Linux inside QEMU. On host side: > >>> > >>> qemu-system-riscv64 -nographic \ > >>> -machine virt \ > >>> -cpu 'rv64,h=true' \ > >>> -smp 8 -m 8G \ > >>> -bios $latest_opensbi \ > >>> -kernel $latest_upstream_linux \ > >>> […snip…] > >>> > >>> Inside that machine, I boot Linux with KVM enabled: > >>> > >>> […] > >>> [ 0.228939] kvm [1]: hypervisor extension available > >>> [ 0.229000] kvm [1]: using Sv48x4 G-stage page table format > >>> [ 0.229033] kvm [1]: VMID 14 bits available > >>> […] > >>> > >>> KVM seems to load correctly. Inside that machine, I compiled QEMU from > >>> the same sources with the KVM accelerator enabled. When I try to start > >>> QEMU with KVM enabled, I get > >>> > >>> ./qemu-system-riscv64 -nographic \ > >>> -monitor none \ > >>> -machine virt \ > >>> -smp 1 -m 1G \ > >>> -bios ./pc-bios/opensbi-riscv64-generic-fw_dynamic.bin \ > >>> -serial stdio \ > >>> -enable-kvm > > > > The QEMU RISC-V KVM support is quite new so I haven't got a chance > > to play with it. > > Btw, the kernel's KVM selftests seem to run. > > > > > Nevertheless, we should not pass any firmware when using KVM > > so can you try "-bios none" ? > > I have no kernel specified in the guest, so I'd then expect to boot into > an completely empty machine (besides the tiny startup stub in the MROM). > However, I still get the exact same error as mentioned in my initial mail.
When KVM is enabled and the kernel is not provided, there is simply nothing in Guest RAM (0x80000000) or ROM (0x00000000) which means you are booting garbage. > > Again, without "-enable-kvm", everything works as expected (i.e., I > don't see any output, because there's basically no guest code to execute). Strange, but even in this case you might be running garbage. > > Just out of curiosity: if you don't pass a bios to the machine, what > would then the boot sequence be? For QEMU KVM: 1) There is no M-mode 2) Guest directly boots in S-mode 3) The SBI services are provided by in-kernel KVM module You need to specify the Guest kernel using "-kernel" parameter when using QEMU KVM. Regards, Anup > > Thanks > Ralf > > > > > Regards, > > Anup > > > >>> > >>> [ 4860.559194] kvm [9942]: VCPU exit error -95 > >>> [ 4860.584262] kvm [9942]: SEPC=0x0 SSTATUS=0x200004120 > >>> HSTATUS=0x2002001c0 > >>> [ 4860.586839] kvm [9942]: SCAUSE=0x14 STVAL=0x0 HTVAL=0x0 HTINST=0x0 > >>> > >>> on the ringbuffer, together with a register dump of qemu [1] on the > >>> console. Needless to say, but without -enable-kvm, it works fine. > >>> > >>> As far as I see that, SCAUSE=0x14 reports a 'Instruction Guest PF', > >>> which would be kind of correct, if the guest's PC really tries to > >>> execute at phys 0x0. DRAM of the 'virt' machine definition should start > >>> at 0x80000000, where OpenSBI resides. So I wonder if an erroneous reset > >>> PC might be the culprit… > >>> > >>> Before digging deeper into that issue, I wanted to ask if Qemu/KVM > >>> inside an emulated riscv64+H-extension is actually supported, or if this > >>> is a known bug and has some ongoing work. > >> > >> RISC-V KVM should work. I haven't had a chance to try it myself though. > >> > >> I have CCed two people who hopefully can help. > >> > >> Alistair > >> > >>> > >>> Thanks > >>> Ralf > >>> > >>> [1] > >>> > >>> pc 0000000000000000 > >>> mhartid 0000000000000000 > >>> mstatus 0000000200000000 > >>> mip 0000000000000000 > >>> mie 0000000000000000 > >>> mideleg 0000000000000000 > >>> medeleg 0000000000000000 > >>> mtvec 0000000000000000 > >>> stvec 0000000000000000 > >>> mepc 0000000000000000 > >>> sepc 0000000000000000 > >>> mcause 0000000000000000 > >>> scause 0000000000000000 > >>> mtval 0000000000000000 > >>> stval 0000000000000000 > >>> mscratch 0000000000000000 > >>> sscratch 0000000000000000 > >>> satp 0000000000000000 > >>> x0/zero 0000000000000000 x1/ra 0000000000000000 x2/sp > >>> 0000000000000000 x3/gp 0000000000000000 > >>> x4/tp 0000000000000000 x5/t0 0000000000000000 x6/t1 > >>> 0000000000000000 x7/t2 0000000000000000 > >>> x8/s0 0000000000000000 x9/s1 0000000000000000 x10/a0 > >>> 0000000000000000 x11/a1 00000000bf000000 > >>> x12/a2 0000000000000000 x13/a3 0000000000000000 x14/a4 > >>> 0000000000000000 x15/a5 0000000000000000 > >>> x16/a6 0000000000000000 x17/a7 0000000000000000 x18/s2 > >>> 0000000000000000 x19/s3 0000000000000000 > >>> x20/s4 0000000000000000 x21/s5 0000000000000000 x22/s6 > >>> 0000000000000000 x23/s7 0000000000000000 > >>> x24/s8 0000000000000000 x25/s9 0000000000000000 x26/s10 > >>> 0000000000000000 x27/s11 0000000000000000 > >>> x28/t3 0000000000000000 x29/t4 0000000000000000 x30/t5 > >>> 0000000000000000 x31/t6 0000000000000000 > >>>
