This patch set provides enough kernel support to allow hosting Xen HVM guests in KVM. It allows hypercalls to be trapped to userspace for handling, uses the existing KVM functions for writing system clock and pvclock information to Xen shared pages, and adds Xen runstate info and event channel upcall vector delivery. It's based on the first section of a patch set that Joao posted as RFC last year^W^W in 2019: https://lore.kernel.org/kvm/20190220201609.28290-1-joao.m.martins@xxxxxxxxxx/ I've updated and reworked the original a bit, including (in my v1): • Support for 32-bit guests • 64-bit second support in wallclock • Time counters for runnable/blocked states in runstate support • Self-tests • Fixed Viridian coexistence • No new KVM_CAP_XEN_xxx, just more bits returned by KVM_CAP_XEN_HVM v2: • Remember the RCU read-critical sections on using the shared info pages • Fix 32-bit build of compat structures (which we use there too) • Use RUNSTATE_blocked as initial state not RUNSTATE_runnable • Include documentation, add cosmetic KVM_XEN_HVM_CONFIG_HYPERCALL_MSR v3: • Stop mapping the shared pages; use kvm_guest_write_cached() instead. • Use kvm_setup_pvclock_page() for Xen pvclock writes too. • Fix CPU numbering confusion and update documentation accordingly. • Support HVMIRQ_callback_vector delivery based on evtchn_upcall_pending. v4: • Rebase on top of the KVM changes merged into 5.11-rc1. • Drop the kvm_{un,}map_gfn() cleanup as it isn't used since v2 anyway. • Trivial cosmetic cleanup (superfluous parens, remove declaration of a function removed in v3, etc.) v5: • Rebased onto kvm/next as of 2021-01-08 (commit 872f36eb0b0f4). • Fix error handling for XEN_HVM_GET_ATTR. • Stop moving struct kvm_host_map definition; it's not used any more. • Add explicit padding to struct kvm_xen_hvm_attr to make it have identical layout on 32-bit vs. 64-bit machines. With the addition in v3 of the callback vector support, we can now successfully boot Linux guests. Other callback types can be handled entirely from userspace, but the vector injection needs kernel support because it doesn't quite work to inject it as ExtINT. We will work on a little bit more event channel offload in future patches, as discussed, but those are purely optimisations. There's a bunch of work for us to do in userspace before those get to the top of our list, and this patch set should be functionally complete as it is. We're working on pushing out rust-vmm support to make use of this, and Joao's qemu patches from last year should still also work with minor tweaks where I've "improved" the KVM←→userspace ABI. David Woodhouse (7): KVM: x86/xen: Fix coexistence of Xen and Hyper-V hypercalls KVM: x86/xen: latch long_mode when hypercall page is set up KVM: x86/xen: add definitions of compat_shared_info, compat_vcpu_info xen: add wc_sec_hi to struct shared_info KVM: x86: declare Xen HVM shared info capability and add test case KVM: Add documentation for Xen hypercall and shared_info updates KVM: x86/xen: Add event channel interrupt vector upcall Joao Martins (9): KVM: x86/xen: fix Xen hypercall page msr handling KVM: x86/xen: intercept xen hypercalls if enabled KVM: x86/xen: add KVM_XEN_HVM_SET_ATTR/KVM_XEN_HVM_GET_ATTR KVM: x86/xen: register shared_info page KVM: x86/xen: update wallclock region KVM: x86/xen: register vcpu info KVM: x86/xen: setup pvclock updates KVM: x86/xen: register vcpu time info region KVM: x86/xen: register runstate info Documentation/virt/kvm/api.rst | 124 +++++- arch/x86/include/asm/kvm_host.h | 24 + arch/x86/include/asm/xen/interface.h | 3 + arch/x86/kvm/Makefile | 2 +- arch/x86/kvm/hyperv.c | 40 +- arch/x86/kvm/irq.c | 7 + arch/x86/kvm/trace.h | 36 ++ arch/x86/kvm/x86.c | 134 ++++-- arch/x86/kvm/x86.h | 1 + arch/x86/kvm/xen.c | 495 +++++++++++++++++++++ arch/x86/kvm/xen.h | 68 +++ include/uapi/linux/kvm.h | 50 +++ include/xen/interface/xen.h | 4 +- tools/testing/selftests/kvm/Makefile | 3 + tools/testing/selftests/kvm/lib/kvm_util.c | 1 + .../testing/selftests/kvm/x86_64/xen_shinfo_test.c | 194 ++++++++ .../testing/selftests/kvm/x86_64/xen_vmcall_test.c | 150 +++++++ 17 files changed, 1273 insertions(+), 63 deletions(-)
