On Fri, Dec 18, 2020 at 02:53:24PM +0100, Greg Kurz wrote:
> Running a guest with 128 NUMA nodes crashes QEMU:
>
> ../../util/error.c:59: error_setv: Assertion `*errp == NULL' failed.
>
> The crash happens when setting the FWNMI migration blocker:
>
> 2861 if (spapr_get_cap(spapr, SPAPR_CAP_FWNMI) == SPAPR_CAP_ON) {
> 2862 /* Create the error string for live migration blocker */
> 2863 error_setg(&spapr->fwnmi_migration_blocker,
> 2864 "A machine check is being handled during migration. The
> handler"
> 2865 "may run and log hardware error on the destination");
> 2866 }
>
> Inspection reveals that papr->fwnmi_migration_blocker isn't NULL:
>
> (gdb) p spapr->fwnmi_migration_blocker
> $1 = (Error *) 0x8000000004000000
>
> Since this is the only place where papr->fwnmi_migration_blocker is
> set, this means someone wrote there in our back. Further analysis
> points to spapr_numa_associativity_init(), especially the part
> that initializes the associative arrays for NVLink GPUs:
>
> max_nodes_with_gpus = nb_numa_nodes + NVGPU_MAX_NUM;
>
> ie. max_nodes_with_gpus = 128 + 6, but the array isn't sized to
> accommodate the 6 extra nodes:
>
> #define MAX_NODES 128
>
> struct SpaprMachineState {
> .
> .
> .
> uint32_t numa_assoc_array[MAX_NODES][NUMA_ASSOC_SIZE];
>
> Error *fwnmi_migration_blocker;
> };
>
> and the following loops happily overwrite spapr->fwnmi_migration_blocker,
> and probably more:
>
> for (i = nb_numa_nodes; i < max_nodes_with_gpus; i++) {
> spapr->numa_assoc_array[i][0] = cpu_to_be32(MAX_DISTANCE_REF_POINTS);
>
> for (j = 1; j < MAX_DISTANCE_REF_POINTS; j++) {
> uint32_t gpu_assoc = smc->pre_5_1_assoc_refpoints ?
> SPAPR_GPU_NUMA_ID : cpu_to_be32(i);
> spapr->numa_assoc_array[i][j] = gpu_assoc;
> }
>
> spapr->numa_assoc_array[i][MAX_DISTANCE_REF_POINTS] = cpu_to_be32(i);
> }
>
> Fix the size of the array. This requires "hw/ppc/spapr.h" to see
> NVGPU_MAX_NUM. Including "hw/pci-host/spapr.h" introduces a
> circular dependency that breaks the build, so this moves the
> definition of NVGPU_MAX_NUM to "hw/ppc/spapr.h" instead.
>
> Reported-by: Min Deng <md...@redhat.com>
> BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1908693
> Fixes: dd7e1d7ae431 ("spapr_numa: move NVLink2 associativity handling to
> spapr_numa.c")
> Cc: danielhb...@gmail.com
> Signed-off-by: Greg Kurz <gr...@kaod.org>
Oof. Applied.
> ---
> include/hw/pci-host/spapr.h | 2 --
> include/hw/ppc/spapr.h | 5 ++++-
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/include/hw/pci-host/spapr.h b/include/hw/pci-host/spapr.h
> index 4f58f0223b56..bd014823a933 100644
> --- a/include/hw/pci-host/spapr.h
> +++ b/include/hw/pci-host/spapr.h
> @@ -115,8 +115,6 @@ struct SpaprPhbState {
> #define SPAPR_PCI_NV2RAM64_WIN_BASE SPAPR_PCI_LIMIT
> #define SPAPR_PCI_NV2RAM64_WIN_SIZE (2 * TiB) /* For up to 6 GPUs 256GB
> each */
>
> -/* Max number of these GPUsper a physical box */
> -#define NVGPU_MAX_NUM 6
> /* Max number of NVLinks per GPU in any physical box */
> #define NVGPU_MAX_LINKS 3
>
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 06a5b4259f20..1cc19575f548 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -112,6 +112,9 @@ typedef enum {
> #define NUMA_ASSOC_SIZE (MAX_DISTANCE_REF_POINTS + 1)
> #define VCPU_ASSOC_SIZE (NUMA_ASSOC_SIZE + 1)
>
> +/* Max number of these GPUsper a physical box */
> +#define NVGPU_MAX_NUM 6
> +
> typedef struct SpaprCapabilities SpaprCapabilities;
> struct SpaprCapabilities {
> uint8_t caps[SPAPR_CAP_NUM];
> @@ -240,7 +243,7 @@ struct SpaprMachineState {
> unsigned gpu_numa_id;
> SpaprTpmProxy *tpm_proxy;
>
> - uint32_t numa_assoc_array[MAX_NODES][NUMA_ASSOC_SIZE];
> + uint32_t numa_assoc_array[MAX_NODES + NVGPU_MAX_NUM][NUMA_ASSOC_SIZE];
>
> Error *fwnmi_migration_blocker;
> };
>
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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