On 11/18/20 6:24 AM, David Gibson wrote: > On Mon, Nov 16, 2020 at 04:34:22PM +0100, Greg Kurz wrote: >> This series was largely built on the assumption that IPI numbers are >> numerically equal to vCPU ids. Even if this happens to be the case >> in practice with the default machine settings, this ceases to be true >> if VSMT is set to a different value than the number of vCPUs per core. >> This causes bogus IPI numbers to be created in KVM from a guest stand >> point. This leads to unknow results in the guest, including crashes >> or missing vCPUs (see BugLink) and even non-fatal oopses in current >> KVM that lacks a check before accessing misconfigured HW (see [1]). >> >> A tentative patch was sent (see [2]) but it seems too complex to be >> merged in an RC. Since the original changes are essentially an >> optimization, it seems safer to revert them for now. The damage is >> done by commit acbdb9956fe9 ("spapr/xive: Allocate IPIs independently >> from the other sources") but the previous patches in the series are >> really preparatory patches. So this reverts the whole series: >> >> eab0a2d06e97 ("spapr/xive: Allocate vCPU IPIs from the vCPU contexts") >> acbdb9956fe9 ("spapr/xive: Allocate IPIs independently from the other >> sources") >> fa94447a2cd6 ("spapr/xive: Use kvmppc_xive_source_reset() in post_load") >> 235d3b116213 ("spapr/xive: Modify kvm_cpu_is_enabled() interface") >> >> [1] https://marc.info/?l=kvm-ppc&m=160458409722959&w=4 >> [2] https://lists.gnu.org/archive/html/qemu-devel/2020-11/msg03626.html >> >> Reported-by: Satheesh Rajendran <sathn...@linux.vnet.ibm.com> >> Fixes: acbdb9956fe9 ("spapr/xive: Allocate IPIs independently from the other >> sources") >> BugLink: https://bugs.launchpad.net/qemu/+bug/1900241 >> Signed-off-by: Greg Kurz <gr...@kaod.org> >> --- >> >> Peter, >> >> I'm Cc'ing you because we really want to fix this regression in 5.2. >> Reverting the culprit optimization seems a lot safer than the changes >> proposed in my other patch. David is on PTO right now and I'm not sure >> if he can post a PR anytime soon. Just in case: would it be acceptable >> to you if I send a PR after it got some positive feedback from the >> people on the Cc: list ? The better the sooner or do we wait for David >> to get a chance to step in ? > > I am indeed on holiday, and I'm not going to review this until next > week. I trust Greg's judgement, though, so I'm happy for this to be > applied directly.
Acked-by: Cédric Le Goater <c...@kaod.org> C. > > >> --- >> hw/intc/spapr_xive_kvm.c | 102 >> ++++++++-------------------------------------- >> 1 file changed, 18 insertions(+), 84 deletions(-) >> >> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c >> index 66bf4c06fe55..e8667ce5f621 100644 >> --- a/hw/intc/spapr_xive_kvm.c >> +++ b/hw/intc/spapr_xive_kvm.c >> @@ -36,9 +36,10 @@ typedef struct KVMEnabledCPU { >> static QLIST_HEAD(, KVMEnabledCPU) >> kvm_enabled_cpus = QLIST_HEAD_INITIALIZER(&kvm_enabled_cpus); >> >> -static bool kvm_cpu_is_enabled(unsigned long vcpu_id) >> +static bool kvm_cpu_is_enabled(CPUState *cs) >> { >> KVMEnabledCPU *enabled_cpu; >> + unsigned long vcpu_id = kvm_arch_vcpu_id(cs); >> >> QLIST_FOREACH(enabled_cpu, &kvm_enabled_cpus, node) { >> if (enabled_cpu->vcpu_id == vcpu_id) { >> @@ -146,45 +147,6 @@ int kvmppc_xive_cpu_synchronize_state(XiveTCTX *tctx, >> Error **errp) >> return s.ret; >> } >> >> -/* >> - * Allocate the vCPU IPIs from the vCPU context. This will allocate >> - * the XIVE IPI interrupt on the chip on which the vCPU is running. >> - * This gives a better distribution of IPIs when the guest has a lot >> - * of vCPUs. When the vCPUs are pinned, this will make the IPI local >> - * to the chip of the vCPU. It will reduce rerouting between interrupt >> - * controllers and gives better performance. >> - */ >> -typedef struct { >> - SpaprXive *xive; >> - Error *err; >> - int rc; >> -} XiveInitIPI; >> - >> -static void kvmppc_xive_reset_ipi_on_cpu(CPUState *cs, run_on_cpu_data arg) >> -{ >> - unsigned long ipi = kvm_arch_vcpu_id(cs); >> - XiveInitIPI *s = arg.host_ptr; >> - uint64_t state = 0; >> - >> - s->rc = kvm_device_access(s->xive->fd, KVM_DEV_XIVE_GRP_SOURCE, ipi, >> - &state, true, &s->err); >> -} >> - >> -static int kvmppc_xive_reset_ipi(SpaprXive *xive, CPUState *cs, Error >> **errp) >> -{ >> - XiveInitIPI s = { >> - .xive = xive, >> - .err = NULL, >> - .rc = 0, >> - }; >> - >> - run_on_cpu(cs, kvmppc_xive_reset_ipi_on_cpu, RUN_ON_CPU_HOST_PTR(&s)); >> - if (s.err) { >> - error_propagate(errp, s.err); >> - } >> - return s.rc; >> -} >> - >> int kvmppc_xive_cpu_connect(XiveTCTX *tctx, Error **errp) >> { >> ERRP_GUARD(); >> @@ -195,7 +157,7 @@ int kvmppc_xive_cpu_connect(XiveTCTX *tctx, Error **errp) >> assert(xive->fd != -1); >> >> /* Check if CPU was hot unplugged and replugged. */ >> - if (kvm_cpu_is_enabled(kvm_arch_vcpu_id(tctx->cs))) { >> + if (kvm_cpu_is_enabled(tctx->cs)) { >> return 0; >> } >> >> @@ -214,12 +176,6 @@ int kvmppc_xive_cpu_connect(XiveTCTX *tctx, Error >> **errp) >> return ret; >> } >> >> - /* Create/reset the vCPU IPI */ >> - ret = kvmppc_xive_reset_ipi(xive, tctx->cs, errp); >> - if (ret < 0) { >> - return ret; >> - } >> - >> kvm_cpu_enable(tctx->cs); >> return 0; >> } >> @@ -279,12 +235,6 @@ int kvmppc_xive_source_reset_one(XiveSource *xsrc, int >> srcno, Error **errp) >> >> assert(xive->fd != -1); >> >> - /* >> - * The vCPU IPIs are now allocated in kvmppc_xive_cpu_connect() >> - * and not with all sources in kvmppc_xive_source_reset() >> - */ >> - assert(srcno >= SPAPR_XIRQ_BASE); >> - >> if (xive_source_irq_is_lsi(xsrc, srcno)) { >> state |= KVM_XIVE_LEVEL_SENSITIVE; >> if (xsrc->status[srcno] & XIVE_STATUS_ASSERTED) { >> @@ -296,28 +246,12 @@ int kvmppc_xive_source_reset_one(XiveSource *xsrc, int >> srcno, Error **errp) >> true, errp); >> } >> >> -/* >> - * To be valid, a source must have been claimed by the machine (valid >> - * entry in the EAS table) and if it is a vCPU IPI, the vCPU should >> - * have been enabled, which means the IPI has been allocated in >> - * kvmppc_xive_cpu_connect(). >> - */ >> -static bool xive_source_is_valid(SpaprXive *xive, int i) >> -{ >> - return xive_eas_is_valid(&xive->eat[i]) && >> - (i >= SPAPR_XIRQ_BASE || kvm_cpu_is_enabled(i)); >> -} >> - >> static int kvmppc_xive_source_reset(XiveSource *xsrc, Error **errp) >> { >> SpaprXive *xive = SPAPR_XIVE(xsrc->xive); >> int i; >> >> - /* >> - * Skip the vCPU IPIs. These are created/reset when the vCPUs are >> - * connected in kvmppc_xive_cpu_connect() >> - */ >> - for (i = SPAPR_XIRQ_BASE; i < xsrc->nr_irqs; i++) { >> + for (i = 0; i < xsrc->nr_irqs; i++) { >> int ret; >> >> if (!xive_eas_is_valid(&xive->eat[i])) { >> @@ -399,7 +333,7 @@ static void kvmppc_xive_source_get_state(XiveSource >> *xsrc) >> for (i = 0; i < xsrc->nr_irqs; i++) { >> uint8_t pq; >> >> - if (!xive_source_is_valid(xive, i)) { >> + if (!xive_eas_is_valid(&xive->eat[i])) { >> continue; >> } >> >> @@ -582,7 +516,7 @@ static void kvmppc_xive_change_state_handler(void >> *opaque, int running, >> uint8_t pq; >> uint8_t old_pq; >> >> - if (!xive_source_is_valid(xive, i)) { >> + if (!xive_eas_is_valid(&xive->eat[i])) { >> continue; >> } >> >> @@ -610,7 +544,7 @@ static void kvmppc_xive_change_state_handler(void >> *opaque, int running, >> for (i = 0; i < xsrc->nr_irqs; i++) { >> uint8_t pq; >> >> - if (!xive_source_is_valid(xive, i)) { >> + if (!xive_eas_is_valid(&xive->eat[i])) { >> continue; >> } >> >> @@ -713,22 +647,22 @@ int kvmppc_xive_post_load(SpaprXive *xive, int >> version_id) >> } >> } >> >> - /* >> - * We can only restore the source config if the source has been >> - * previously set in KVM. Since we don't do that at reset time >> - * when restoring a VM, let's do it now. >> - */ >> - ret = kvmppc_xive_source_reset(&xive->source, &local_err); >> - if (ret < 0) { >> - goto fail; >> - } >> - >> /* Restore the EAT */ >> for (i = 0; i < xive->nr_irqs; i++) { >> - if (!xive_source_is_valid(xive, i)) { >> + if (!xive_eas_is_valid(&xive->eat[i])) { >> continue; >> } >> >> + /* >> + * We can only restore the source config if the source has been >> + * previously set in KVM. Since we don't do that for all interrupts >> + * at reset time anymore, let's do it now. >> + */ >> + ret = kvmppc_xive_source_reset_one(&xive->source, i, &local_err); >> + if (ret < 0) { >> + goto fail; >> + } >> + >> ret = kvmppc_xive_set_source_config(xive, i, &xive->eat[i], >> &local_err); >> if (ret < 0) { >> goto fail; >> >> >