From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43740) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c6m3W-0001XN-Fb for qemu-devel@nongnu.org; Tue, 15 Nov 2016 17:18:20 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c6m3U-00038f-LJ for qemu-devel@nongnu.org; Tue, 15 Nov 2016 17:18:18 -0500 From: David Gibson Date: Wed, 16 Nov 2016 09:17:55 +1100 Message-Id: <1479248275-18889-13-git-send-email-david@gibson.dropbear.id.au> In-Reply-To: <1479248275-18889-1-git-send-email-david@gibson.dropbear.id.au> References: <1479248275-18889-1-git-send-email-david@gibson.dropbear.id.au> Subject: [Qemu-devel] [RFCv2 12/12] ppc: Rework CPU compatibility testing across migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: groug@kaod.org, clg@kaod.org, aik@ozlabs.ru, mdroth@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com Cc: agraf@suse.de, qemu-ppc@nongnu.org, qemu-devel@nongnu.org, abologna@redhat.com, thuth@redhat.com, lvivier@redhat.com, David Gibson Migrating between different CPU versions is quite complicated for ppc. A long time ago, we ensure identical CPU versions at either end by checking the PVR had the same value. However, this breaks under KVM HV, because we always have to use the host's PVR - it's not virtualized. That would mean we couldn't migrate between hosts with different PVRs, even if the CPUs are close enough to compatible in practice (sometimes identical cores with different surrounding logic have different PVRs, so this happens in practice quite often). So, we removed the PVR check, but instead checked that several flags indicating supported instructions matched. This turns out to be a bad idea, because those instruction masks are not architected information, but essentially a TCG implementation detail. So changes to qemu internal CPU modelling can break migration - this happened between qemu-2.6 and qemu-2.7. Modern server-class CPUs can be placed into compatibility modes. Now that we're handling those properly, we finally have the information to sanely deal with CPU compatibility across migration. This patch bumps the migration version number for the ppc CPU removing the instruction mask field (and some other unwise VMSTATE_EQUAL checks), and adding the compatibility PVR to the migration stream. We consider the CPUs compatible for migration if: * The source was running in a compatibility mode which the destination supports OR * The source has a PVR matching the same qemu CPU class as the destination, either an exact match or an approximate match determined by the cpu class's pvr_match hook. Signed-off-by: David Gibson --- target-ppc/machine.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 79 insertions(+), 8 deletions(-) diff --git a/target-ppc/machine.c b/target-ppc/machine.c index e43cb6c..25a30d5 100644 --- a/target-ppc/machine.c +++ b/target-ppc/machine.c @@ -8,6 +8,7 @@ #include "helper_regs.h" #include "mmu-hash64.h" #include "migration/cpu.h" +#include "qapi/error.h" static int cpu_load_old(QEMUFile *f, void *opaque, int version_id) { @@ -163,6 +164,30 @@ static void cpu_pre_save(void *opaque) } } +/* + * Determine if a given PVR is a "close enough" match to the CPU + * object. For TCG and KVM PR it would probably be sufficient to + * require an exact PVR match. However for KVM HV the user is + * restricted to a PVR exactly matching the host CPU. The correct way + * to handle this is to put the guest into an architected + * compatibility mode. However, to allow a more forgiving transition + * and migration from before this was widely done, we allow migration + * between sufficiently similar PVRs, as determined by the CPU class's + * pvr_match() hook. + */ +static bool pvr_match(PowerPCCPU *cpu, uint32_t pvr) +{ + PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu); + + if (pvr == pcc->pvr) { + return true; + } + if (pcc->pvr_match) { + return pcc->pvr_match(pcc, pvr); + } + return false; +} + static int cpu_post_load(void *opaque, int version_id) { PowerPCCPU *cpu = opaque; @@ -171,10 +196,31 @@ static int cpu_post_load(void *opaque, int version_id) target_ulong msr; /* - * We always ignore the source PVR. The user or management - * software has to take care of running QEMU in a compatible mode. + * If we're operating in compat mode, we should be ok as long as + * the destination supports the same compatiblity mode. + * + * Otherwise, however, we require that the destination has exactly + * the same CPU model as the source. */ - env->spr[SPR_PVR] = env->spr_cb[SPR_PVR].default_value; + +#if defined(TARGET_PPC64) + if (cpu->compat_pvr) { + Error *local_err = NULL; + + ppc_set_compat(cpu, cpu->compat_pvr, &local_err); + if (local_err) { + error_report_err(local_err); + error_free(local_err); + return -1; + } + } else +#endif + { + if (!pvr_match(cpu, env->spr[SPR_PVR])) { + return -1; + } + } + env->lr = env->spr[SPR_LR]; env->ctr = env->spr[SPR_CTR]; cpu_write_xer(env, env->spr[SPR_XER]); @@ -527,9 +573,32 @@ static const VMStateDescription vmstate_tlbmas = { } }; +static bool compat_needed(void *opaque) +{ + PowerPCCPU *cpu = opaque; + + return cpu->vhyp != NULL; +} + +static const VMStateDescription vmstate_compat = { + .name = "cpu/compat", + .version_id = 1, + .minimum_version_id = 1, + .needed = compat_needed, + .fields = (VMStateField[]) { + VMSTATE_UINT32(compat_pvr, PowerPCCPU), + VMSTATE_END_OF_LIST() + } +}; + +static bool version_before_6(void *opaque, int version_id) +{ + return version_id < 6; +} + const VMStateDescription vmstate_ppc_cpu = { .name = "cpu", - .version_id = 5, + .version_id = 6, .minimum_version_id = 5, .minimum_version_id_old = 4, .load_state_old = cpu_load_old, @@ -561,10 +630,11 @@ const VMStateDescription vmstate_ppc_cpu = { /* FIXME: access_type? */ /* Sanity checking */ - VMSTATE_UINTTL_EQUAL(env.msr_mask, PowerPCCPU), - VMSTATE_UINT64_EQUAL(env.insns_flags, PowerPCCPU), - VMSTATE_UINT64_EQUAL(env.insns_flags2, PowerPCCPU), - VMSTATE_UINT32_EQUAL(env.nb_BATs, PowerPCCPU), + VMSTATE_UNUSED_TEST(version_before_6, + sizeof(target_ulong) /* msr_mask */ + + sizeof(uint64_t) /* insns_flags */ + + sizeof(uint64_t) /* insns_flags2 */ + + sizeof(uint32_t)), /* nb_BATs */ VMSTATE_END_OF_LIST() }, .subsections = (const VMStateDescription*[]) { @@ -579,6 +649,7 @@ const VMStateDescription vmstate_ppc_cpu = { &vmstate_tlb6xx, &vmstate_tlbemb, &vmstate_tlbmas, + &vmstate_compat, NULL } }; -- 2.7.4