This is a note to let you know that I've just added the patch titled MIPS: KVM: Handle MSA Disabled exceptions from guest to the 3.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mips-kvm-handle-msa-disabled-exceptions-from-guest.patch and it can be found in the queue-3.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 98119ad53376885819d93dfb8737b6a9a61ca0ba Mon Sep 17 00:00:00 2001 From: James Hogan <james.hogan@xxxxxxxxxx> Date: Fri, 6 Feb 2015 11:11:56 +0000 Subject: MIPS: KVM: Handle MSA Disabled exceptions from guest From: James Hogan <james.hogan@xxxxxxxxxx> commit 98119ad53376885819d93dfb8737b6a9a61ca0ba upstream. Guest user mode can generate a guest MSA Disabled exception on an MSA capable core by simply trying to execute an MSA instruction. Since this exception is unknown to KVM it will be passed on to the guest kernel. However guest Linux kernels prior to v3.15 do not set up an exception handler for the MSA Disabled exception as they don't support any MSA capable cores. This results in a guest OS panic. Since an older processor ID may be being emulated, and MSA support is not advertised to the guest, the correct behaviour is to generate a Reserved Instruction exception in the guest kernel so it can send the guest process an illegal instruction signal (SIGILL), as would happen with a non-MSA-capable core. Fix this as minimally as reasonably possible by preventing kvm_mips_check_privilege() from relaying MSA Disabled exceptions from guest user mode to the guest kernel, and handling the MSA Disabled exception by emulating a Reserved Instruction exception in the guest, via a new handle_msa_disabled() KVM callback. Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Paul Burton <paul.burton@xxxxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: Gleb Natapov <gleb@xxxxxxxxxx> Cc: linux-mips@xxxxxxxxxxxxxx Cc: kvm@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/mips/include/asm/kvm_host.h | 2 ++ arch/mips/kvm/emulate.c | 1 + arch/mips/kvm/mips.c | 4 ++++ arch/mips/kvm/trap_emul.c | 28 ++++++++++++++++++++++++++++ 4 files changed, 35 insertions(+) --- a/arch/mips/include/asm/kvm_host.h +++ b/arch/mips/include/asm/kvm_host.h @@ -321,6 +321,7 @@ enum mips_mmu_types { #define T_TRAP 13 /* Trap instruction */ #define T_VCEI 14 /* Virtual coherency exception */ #define T_FPE 15 /* Floating point exception */ +#define T_MSADIS 21 /* MSA disabled exception */ #define T_WATCH 23 /* Watch address reference */ #define T_VCED 31 /* Virtual coherency data */ @@ -577,6 +578,7 @@ struct kvm_mips_callbacks { int (*handle_syscall)(struct kvm_vcpu *vcpu); int (*handle_res_inst)(struct kvm_vcpu *vcpu); int (*handle_break)(struct kvm_vcpu *vcpu); + int (*handle_msa_disabled)(struct kvm_vcpu *vcpu); int (*vm_init)(struct kvm *kvm); int (*vcpu_init)(struct kvm_vcpu *vcpu); int (*vcpu_setup)(struct kvm_vcpu *vcpu); --- a/arch/mips/kvm/emulate.c +++ b/arch/mips/kvm/emulate.c @@ -2176,6 +2176,7 @@ enum emulation_result kvm_mips_check_pri case T_SYSCALL: case T_BREAK: case T_RES_INST: + case T_MSADIS: break; case T_COP_UNUSABLE: --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -1119,6 +1119,10 @@ int kvm_mips_handle_exit(struct kvm_run ret = kvm_mips_callbacks->handle_break(vcpu); break; + case T_MSADIS: + ret = kvm_mips_callbacks->handle_msa_disabled(vcpu); + break; + default: kvm_err("Exception Code: %d, not yet handled, @ PC: %p, inst: 0x%08x BadVaddr: %#lx Status: %#lx\n", exccode, opc, kvm_get_inst(opc, vcpu), badvaddr, --- a/arch/mips/kvm/trap_emul.c +++ b/arch/mips/kvm/trap_emul.c @@ -330,6 +330,33 @@ static int kvm_trap_emul_handle_break(st return ret; } +static int kvm_trap_emul_handle_msa_disabled(struct kvm_vcpu *vcpu) +{ + struct kvm_run *run = vcpu->run; + uint32_t __user *opc = (uint32_t __user *) vcpu->arch.pc; + unsigned long cause = vcpu->arch.host_cp0_cause; + enum emulation_result er = EMULATE_DONE; + int ret = RESUME_GUEST; + + /* No MSA supported in guest, guest reserved instruction exception */ + er = kvm_mips_emulate_ri_exc(cause, opc, run, vcpu); + + switch (er) { + case EMULATE_DONE: + ret = RESUME_GUEST; + break; + + case EMULATE_FAIL: + run->exit_reason = KVM_EXIT_INTERNAL_ERROR; + ret = RESUME_HOST; + break; + + default: + BUG(); + } + return ret; +} + static int kvm_trap_emul_vm_init(struct kvm *kvm) { return 0; @@ -470,6 +497,7 @@ static struct kvm_mips_callbacks kvm_tra .handle_syscall = kvm_trap_emul_handle_syscall, .handle_res_inst = kvm_trap_emul_handle_res_inst, .handle_break = kvm_trap_emul_handle_break, + .handle_msa_disabled = kvm_trap_emul_handle_msa_disabled, .vm_init = kvm_trap_emul_vm_init, .vcpu_init = kvm_trap_emul_vcpu_init, Patches currently in stable-queue which might be from james.hogan@xxxxxxxxxx are queue-3.19/mips-lose_fpu-disable-fpu-when-msa-enabled.patch queue-3.19/mips-kvm-handle-msa-disabled-exceptions-from-guest.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html