On Fri, Apr 06, 2018 at 02:14:09PM +1000, Nicholas Piggin wrote:
> It's possible to take a SRESET or MCE in these paths due to a bug
> in the host code or a NMI IPI etc. A recent bug attempting to load
> a virtual address gave a complete but cryptic error, abridged:
>
> Oops: Bad interrupt in KVM entry/exit code, sig: 6 [#1]
> LE SMP NR_CPUS=2048 NUMA PowerNV
> CPU: 53 PID: 6582 Comm: qemu-system-ppc Not tainted
> NIP: c0000000000155ac LR: c0000000000c2430 CTR: c000000000015580
> REGS: c000000fff76dd80 TRAP: 0200 Not tainted
> MSR: 9000000000201003 <SF,HV,ME,RI,LE> CR: 48082222 XER: 00000000
> CFAR: 0000000102900ef0 DAR: d00017fffd941a28 DSISR: 00000040 SOFTE: 3
> NIP [c0000000000155ac] perf_trace_tlbie+0x2c/0x1a0
> LR [c0000000000c2430] do_tlbies+0x230/0x2f0
>
> Sending NMIs through the Linux handlers gives a nicer output:
>
> Severe Machine check interrupt [Not recovered]
> NIP [c0000000000155ac]: perf_trace_tlbie+0x2c/0x1a0
> Initiator: CPU
> Error type: Real address [Load (bad)]
> Effective address: d00017fffcc01a28
> opal: Machine check interrupt unrecoverable: MSR(RI=0)
> opal: Hardware platform error: Unrecoverable Machine Check exception
> CPU: 0 PID: 6700 Comm: qemu-system-ppc Tainted: G M
> NIP: c0000000000155ac LR: c0000000000c23c0 CTR: c000000000015580
> REGS: c000000fff9e9d80 TRAP: 0200 Tainted: G M
> MSR: 9000000000201001 <SF,HV,ME,LE> CR: 48082222 XER: 00000000
> CFAR: 000000010cbc1a30 DAR: d00017fffcc01a28 DSISR: 00000040 SOFTE: 3
> NIP [c0000000000155ac] perf_trace_tlbie+0x2c/0x1a0
> LR [c0000000000c23c0] do_tlbies+0x1c0/0x280
>
> Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> ---
> This is lightly tested only, not sure if there would be a better way
> to do it?
The patch seems reasonable. I have just one comment below. Do you
want to re-send it without the RFC tag, or should I just take it?
> arch/powerpc/kvm/book3s_hv_builtin.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c
> index de18299f92b7..0b9b8e188bfa 100644
> --- a/arch/powerpc/kvm/book3s_hv_builtin.c
> +++ b/arch/powerpc/kvm/book3s_hv_builtin.c
> @@ -18,6 +18,7 @@
> #include <linux/cma.h>
> #include <linux/bitops.h>
>
> +#include <asm/asm-prototypes.h>
> #include <asm/cputable.h>
> #include <asm/kvm_ppc.h>
> #include <asm/kvm_book3s.h>
> @@ -633,6 +634,17 @@ int kvmppc_rm_h_eoi(struct kvm_vcpu *vcpu, unsigned long xirr)
>
> void kvmppc_bad_interrupt(struct pt_regs *regs)
> {
> + regs->msr &= ~MSR_RI;
This is worth mentioning in the commit message. I assume you're doing
it to make sure we won't try to continue execution under any
circumstances?
> + /*
> + * 100 could happen at any time, 200 can happen due to
> + * invalid real address access for example.
> + */
> + if (TRAP(regs) == 0x100) {
> + get_paca()->in_nmi++;
> + system_reset_exception(regs);
> + }
> + if (TRAP(regs) == 0x200)
> + machine_check_exception(regs);
> die("Bad interrupt in KVM entry/exit code", regs, SIGABRT);
> panic("Bad KVM trap");
> }
> --
> 2.16.3
Paul.
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