Howdy, Ben reminded me a while back that we have a nasty race in our KVM PV code. We replace a few instructions with longer streams of instructions to check whether it's necessary to trap out from it (like mtmsr, no need to trap if we only disable interrupts). During those replacement chunks we must not get any interrupts, because they might overwrite scratch space that we already used to save otherwise clobbered register state into. So we have a thing called "critical sections" which allows us to atomically get in and out of "interrupt disabled" modes without touching MSR. When we are supposed to deliver an interrupt into the guest while we are in a critical section, we just don't inject the interrupt yet, but leave it be until the next trap. However, we never really know when the next trap would be. For all we know it could be never. At this point we created a race that is a potential source for interrupt loss or at least deferral. This patch set aims at solving the race. Instead of merely deferring an interrupt when we see such a situation, we go into a special instruction interpretation mode. In this mode, we interpret all PPC assembler instructions that happen until we are out of the critical section again, at which point we can now inject the interrupt. This bug only affects KVM implementations that make use of the magic page, so e500v2, book3s_32 and book3s_64 PR KVM. Alex Alexander Graf (33): KVM: PPC: Implement kvmppc_xlate for all targets KVM: PPC: Move kvmppc_ld/st to common code KVM: PPC: Remove kvmppc_bad_hva() KVM: PPC: Propagate kvmppc_xlate errors properly KVM: PPC: Use kvm_read_guest in kvmppc_ld KVM: PPC: Handle magic page in kvmppc_ld/st KVM: PPC: Separate loadstore emulation from priv emulation KVM: PPC: Introduce emulation for unprivileged instructions KVM: PPC: Move critical section detection to common code KVM: PPC: Make critical section detection conditional KVM: PPC: BookE: Use common critical section helper KVM: PPC: Emulate critical sections when we hit them KVM: PPC: Expose helper functions for data/inst faults KVM: PPC: Add std instruction emulation KVM: PPC: Add stw instruction emulation KVM: PPC: Add ld instruction emulation KVM: PPC: Add lwz instruction emulation KVM: PPC: Add mfcr instruction emulation KVM: PPC: Add addis instruction emulation KVM: PPC: Add ori instruction emulation KVM: PPC: Add and instruction emulation KVM: PPC: Add andi. instruction emulation KVM: PPC: Add or instruction emulation KVM: PPC: Add cmpwi/cmpdi instruction emulation KVM: PPC: Add bc instruction emulation KVM: PPC: Add mtcrf instruction emulation KVM: PPC: Add xor instruction emulation KVM: PPC: Add oris instruction emulation KVM: PPC: Add rldicr/rldicl/rldic instruction emulation KVM: PPC: Add rlwimi instruction emulation KVM: PPC: Add rlwinm instruction emulation KVM: PPC: Handle NV registers in emulated critical sections KVM: PPC: Enable critical section emulation arch/powerpc/include/asm/kvm_book3s.h | 9 +- arch/powerpc/include/asm/kvm_booke.h | 10 + arch/powerpc/include/asm/kvm_host.h | 4 +- arch/powerpc/include/asm/kvm_ppc.h | 29 ++ arch/powerpc/include/asm/ppc-opcode.h | 14 + arch/powerpc/kvm/Makefile | 4 +- arch/powerpc/kvm/book3s.c | 142 ++------ arch/powerpc/kvm/book3s_pr.c | 16 +- arch/powerpc/kvm/booke.c | 120 +++++-- arch/powerpc/kvm/emulate.c | 656 ++++++++++++++++++++++++---------- arch/powerpc/kvm/emulate_loadstore.c | 266 ++++++++++++++ arch/powerpc/kvm/powerpc.c | 123 ++++++- 12 files changed, 1076 insertions(+), 317 deletions(-) create mode 100644 arch/powerpc/kvm/emulate_loadstore.c -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
