Re: [PATCH 0/15] KVM: MIPS: Add Loongson-3 support (Host Side)

[Huacai Chen]

Hi, Jiaxun,

On Mon, Apr 13, 2020 at 4:19 PM Jiaxun Yang <address@hidden> wrote:
>
> On Mon, 13 Apr 2020 15:30:09 +0800
> Huacai Chen <address@hidden> wrote:
>
> > We are preparing to add KVM support for Loongson-3. VZ extension is
> > fully supported in Loongson-3A R4+, and we will not care about old
> > CPUs (at least now). We already have a full functional Linux kernel
> > (based on Linux-5.4.x LTS) and QEMU (based on 5.0.0-rc2) and their git
> > repositories are here:
> >
> > QEMU: https://github.com/chenhuacai/qemu
> > Kernel: https://github.com/chenhuacai/linux
> >
> > Of course these two repositories need to be rework and not suitable
> > for upstream (especially the commits need to be splitted). We show
> > them here is just to tell others what we have done, and how
> > KVM/Loongson will look like.
> >
> > Our plan is make the KVM host side be upstream first, and after that,
> > we will make the KVM guest side and QEMU emulator be upstream.
>
> + Aleksandar as QEMU/MIPS mainatiner
>
> I was involved in KVM/Loongson development a bit and also intend to
> help with mainline these works.
>
> After dealing with basic LS7A PCH kernel support, I'm going to
> cooperate with Huacai and anyone who interested in to deal with
> following stuff:
>
> - Basic QEMU/TCG support for Loongson64 instructions.
>         Well, it seems unrelated with KVM, but that would make
>         development easier with cross ISA emulation. I'm not going to
>         implement all the features like Loongson's page table fast walk
>         extension and binary translation extension but I'll ensure any
>         binary compiled with march=loongson3a can run flawlessly on
>         TCG.
>
> - Design of Loongson-VIRT QEMU machine
>         It is nearly impossible to bring a real Loongson system into
>         QEMU. Both RS780E and LS7A PCH have tons of unreasonable design
>         that would make the emulation extremely complex, Loongson
>         company's KVM implementation[1] has already proofed that,
>         thay're now in the hell. So we all agreed that we should build
>         a machine from draft. I think we should reuse existing infra as
>         far as possible to reduce our work load. I'm planing to use
>         pci-host-cam-generic together with VIRTIO PCI devices and a
>         a strip down version of loongson,liointc-1.0a to build a pure
>         PCI based system. But if any one have better idea please just
>         tell us, I'm still considering how to implement SMP-IPI and ACPI
>         stuff.
>
> - BIOS in VM
>         This has a lower priority. But BIOS is required to make a
>         emulated machine looks like a real machine. Loongson have their
>         open-sourced PMON and close-sourced UEFI(Based on tianocore).
>         I'd really with Loongson or Lemote will open-source their UEFI
>         but PMON is also a option.
There will be an open source BIOS, we have completed 98%.

>
> Any kind of feedback is appreciated.
>
> Thanks.
>
> Wish you good health :-)
>
>
> [1]: http://cgit.loongnix.org/cgit/linux-3.10/ &
> http://cgit.loongnix.org/cgit/qemu-2.7.0/
>
> Btw: I think Cc qemu-devel for the whole series is a little bit
> disturb, probably we should only Cc qemu-devel for the cover letter.
Sorrry, its my mistake.

>
> >
> > Mike Rapoport(1):
> >  mips: define pud_index() regardless of page table folding
> >
> > Xing Li(2):
> >  KVM: MIPS: Define KVM_ENTRYHI_ASID to cpu_asid_mask(&boot_cpu_data)
> >  KVM: MIPS: Fix VPN2_MASK definition for variable cpu_vmbits
> >
> > Huacai Chen(12):
> >  KVM: MIPS: Increase KVM_MAX_VCPUS and KVM_USER_MEM_SLOTS to 16
> >  KVM: MIPS: Add EVENTFD support which is needed by VHOST
> >  KVM: MIPS: Use lddir/ldpte instructions to lookup gpa_mm.pgd
> >  KVM: MIPS: Introduce and use cpu_guest_has_ldpte
> >  KVM: MIPS: Use root tlb to control guest's CCA for Loongson-3
> >  KVM: MIPS: Let indexed cacheops cause guest exit on Loongson-3
> >  KVM: MIPS: Add more types of virtual interrupts
> >  KVM: MIPS: Add Loongson-3 Virtual IPI interrupt support
> >  KVM: MIPS: Add CPUCFG emulation for Loongson-3
> >  KVM: MIPS: Add CONFIG6 and DIAG registers emulation
> >  KVM: MIPS: Add more MMIO load/store instructions emulation
> >  KVM: MIPS: Enable KVM support for Loongson-3
> >
> > Signed-off-by: Huacai Chen <address@hidden>
> > ---
> >  arch/mips/Kconfig                    |   1 +
> >  arch/mips/include/asm/cpu-features.h |   3 +
> >  arch/mips/include/asm/kvm_host.h     |  50 +++-
> >  arch/mips/include/asm/mipsregs.h     |   7 +
> >  arch/mips/include/asm/pgtable-64.h   |   4 +-
> >  arch/mips/include/uapi/asm/inst.h    |  11 +
> >  arch/mips/kernel/cpu-probe.c         |   2 +
> >  arch/mips/kvm/Kconfig                |   1 +
> >  arch/mips/kvm/Makefile               |   5 +-
> >  arch/mips/kvm/emulate.c              | 461
> > ++++++++++++++++++++++++++++++++++- arch/mips/kvm/entry.c
> >    |  19 +- arch/mips/kvm/interrupt.c            |  93 +------
> >  arch/mips/kvm/interrupt.h            |  14 +-
> >  arch/mips/kvm/loongson_ipi.c         | 215 ++++++++++++++++
> >  arch/mips/kvm/mips.c                 |  49 +++-
> >  arch/mips/kvm/tlb.c                  |  39 +++
> >  arch/mips/kvm/trap_emul.c            |   3 +
> >  arch/mips/kvm/vz.c                   | 204 +++++++++++-----
> >  18 files changed, 1013 insertions(+), 168 deletions(-)
> >  create mode 100644 arch/mips/kvm/loongson_ipi.c
> > --
> > 2.7.0
>
Huacai