ACK: [SRU][Xenial][PATCH 1/1] KVM: PPC: Book3S HV: Enable TM before accessing TM registers

[Stefan Bader]

On 05.09.2017 02:06, Daniel Axtens wrote:
> BugLink: https://bugs.launchpad.net/bugs/1714420
> 
> Commit 46a704f8409f ("KVM: PPC: Book3S HV: Preserve userspace HTM state
> properly", 2017-06-15) added code to read transactional memory (TM)
> registers but forgot to enable TM before doing so.  The result is
> that if userspace does have live values in the TM registers, a KVM_RUN
> ioctl will cause a host kernel crash like this:
> 
> [  181.328511] Unrecoverable TM Unavailable Exception f60 at d00000001e7d9980
> [  181.328605] Oops: Unrecoverable TM Unavailable Exception, sig: 6 [#1]
> [  181.328613] SMP NR_CPUS=2048
> [  181.328613] NUMA
> [  181.328618] PowerNV
> [  181.328646] Modules linked in: vhost_net vhost tap nfs_layout_nfsv41_files rpcsec_gss_krb5 nfsv4 dns_resolver nfs
> +fscache xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat
> +nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 tun ebtable_filter ebtables
> +ip6table_filter ip6_tables iptable_filter bridge stp llc kvm_hv kvm nfsd ses enclosure scsi_transport_sas ghash_generic
> +auth_rpcgss gf128mul xts sg ctr nfs_acl lockd vmx_crypto shpchp ipmi_powernv i2c_opal grace ipmi_devintf i2c_core
> +powernv_rng sunrpc ipmi_msghandler ibmpowernv uio_pdrv_genirq uio leds_powernv powernv_op_panel ip_tables xfs sd_mod
> +lpfc ipr bnx2x libata mdio ptp pps_core scsi_transport_fc libcrc32c dm_mirror dm_region_hash dm_log dm_mod
> [  181.329278] CPU: 40 PID: 9926 Comm: CPU 0/KVM Not tainted 4.12.0+ #1
> [  181.329337] task: c000003fc6980000 task.stack: c000003fe4d80000
> [  181.329396] NIP: d00000001e7d9980 LR: d00000001e77381c CTR: d00000001e7d98f0
> [  181.329465] REGS: c000003fe4d837e0 TRAP: 0f60   Not tainted  (4.12.0+)
> [  181.329523] MSR: 9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE>
> [  181.329527]   CR: 24022448  XER: 00000000
> [  181.329608] CFAR: d00000001e773818 SOFTE: 1
> [  181.329608] GPR00: d00000001e77381c c000003fe4d83a60 d00000001e7ef410 c000003fdcfe0000
> [  181.329608] GPR04: c000003fe4f00000 0000000000000000 0000000000000000 c000003fd7954800
> [  181.329608] GPR08: 0000000000000001 c000003fc6980000 0000000000000000 d00000001e7e2880
> [  181.329608] GPR12: d00000001e7d98f0 c000000007b19000 00000001295220e0 00007fffc0ce2090
> [  181.329608] GPR16: 0000010011886608 00007fff8c89f260 0000000000000001 00007fff8c080028
> [  181.329608] GPR20: 0000000000000000 00000100118500a6 0000010011850000 0000010011850000
> [  181.329608] GPR24: 00007fffc0ce1b48 0000010011850000 00000000d673b901 0000000000000000
> [  181.329608] GPR28: 0000000000000000 c000003fdcfe0000 c000003fdcfe0000 c000003fe4f00000
> [  181.330199] NIP [d00000001e7d9980] kvmppc_vcpu_run_hv+0x90/0x6b0 [kvm_hv]
> [  181.330264] LR [d00000001e77381c] kvmppc_vcpu_run+0x2c/0x40 [kvm]
> [  181.330322] Call Trace:
> [  181.330351] [c000003fe4d83a60] [d00000001e773478] kvmppc_set_one_reg+0x48/0x340 [kvm] (unreliable)
> [  181.330437] [c000003fe4d83b30] [d00000001e77381c] kvmppc_vcpu_run+0x2c/0x40 [kvm]
> [  181.330513] [c000003fe4d83b50] [d00000001e7700b4] kvm_arch_vcpu_ioctl_run+0x114/0x2a0 [kvm]
> [  181.330586] [c000003fe4d83bd0] [d00000001e7642f8] kvm_vcpu_ioctl+0x598/0x7a0 [kvm]
> [  181.330658] [c000003fe4d83d40] [c0000000003451b8] do_vfs_ioctl+0xc8/0x8b0
> [  181.330717] [c000003fe4d83de0] [c000000000345a64] SyS_ioctl+0xc4/0x120
> [  181.330776] [c000003fe4d83e30] [c00000000000b004] system_call+0x58/0x6c
> [  181.330833] Instruction dump:
> [  181.330869] e92d0260 e9290b50 e9290108 792807e3 41820058 e92d0260 e9290b50 e9290108
> [  181.330941] 792ae8a4 794a1f87 408204f4 e92d0260 <7d4022a6> f9490ff0 e92d0260 7d4122a6
> [  181.331013] ---[ end trace 6f6ddeb4bfe92a92 ]---
> 
> The fix is just to turn on the TM bit in the MSR before accessing the
> registers.
> 
> Cc: stable at vger.kernel.org # v3.14+
> Fixes: 46a704f8409f ("KVM: PPC: Book3S HV: Preserve userspace HTM state properly")
> Reported-by: Jan Stancek <jstancek at redhat.com>
> Tested-by: Jan Stancek <jstancek at redhat.com>
> Signed-off-by: Paul Mackerras <paulus at ozlabs.org>
> (cherry picked from commit e47057151422a67ce08747176fa21cb3b526a2c9)
> Signed-off-by: Daniel Axtens <daniel.axtens at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---
>  arch/powerpc/kvm/book3s_hv.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 0283de0fe7d0..36e841e10db1 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -2708,6 +2708,8 @@ static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct kvm_vcpu *vcpu)
>  			run->fail_entry.hardware_entry_failure_reason = 0;
>  			return -EINVAL;
>  		}
> +		/* Enable TM so we can read the TM SPRs */
> +		mtmsr(mfmsr() | MSR_TM);
>  		current->thread.tm_tfhar = mfspr(SPRN_TFHAR);
>  		current->thread.tm_tfiar = mfspr(SPRN_TFIAR);
>  		current->thread.tm_texasr = mfspr(SPRN_TEXASR);
> 


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