On Sun, Jan 14, 2018 at 05:23:49PM -0200, Jose Ricardo Ziviani wrote: > QEMU currently checks whether SMT passed is valid or not. However, it > doesn't check if KVM supports such mode when kvm is enabled.
That's not really true - the attempt to actually set the vsmt mode in
KVM later on in spapr_set_vsmt_mode() will fail if KVM can't support
the number of threads.
The error added here might be a bit easier to understand, since it
doesn't refer to vsmt modes, which might just confuse the issue.
The change isn't urgent, though.
> This patch relies on KVM_CAP_PPC_SMT_POSSIBLE to make it sure that QEMU
> will either set a valid SMT mode or warn an error message and quit.
>
> Signed-off-by: Jose Ricardo Ziviani <jos...@linux.vnet.ibm.com>
> ---
> hw/ppc/spapr.c | 10 ++++++++++
> target/ppc/kvm.c | 5 +++++
> target/ppc/kvm_ppc.h | 6 ++++++
> 3 files changed, 21 insertions(+)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index d1acfe8858..aed4d25fc4 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2261,12 +2261,22 @@ static void spapr_set_vsmt_mode(sPAPRMachineState
> *spapr, Error **errp)
> "on a pseries machine");
> goto out;
> }
> +
> if (!is_power_of_2(smp_threads)) {
> error_setg(&local_err, "Cannot support %d threads/core on a pseries "
> "machine because it must be a power of 2", smp_threads);
> goto out;
> }
>
> + if (kvm_enabled() && kvmppc_cap_smt_possible() > 0) {
> + if ((kvmppc_cap_smt_possible() & smp_threads) != smp_threads) {
> + error_setg(&local_err, "KVM does not support %d threads/core.",
> + smp_threads);
> + kvmppc_hint_smt_possible(&local_err);
> + goto out;
> + }
> + }
I'd like to see a fallback for kernels that don't support the
smt_possible cap and vsmt mode setting (for those, we must have
smp_threads <= kvm_smt).
> +
> /* Detemine the VSMT mode to use: */
> if (vsmt_user) {
> if (spapr->vsmt < smp_threads) {
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index 914be687e7..4a8ff4d63c 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -2456,6 +2456,11 @@ bool kvmppc_has_cap_mmu_hash_v3(void)
> return cap_mmu_hash_v3;
> }
>
> +int kvmppc_cap_smt_possible(void)
> +{
> + return cap_ppc_smt_possible;
> +}
> +
> PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void)
> {
> uint32_t host_pvr = mfpvr();
> diff --git a/target/ppc/kvm_ppc.h b/target/ppc/kvm_ppc.h
> index ecb55493cc..2221850723 100644
> --- a/target/ppc/kvm_ppc.h
> +++ b/target/ppc/kvm_ppc.h
> @@ -59,6 +59,7 @@ bool kvmppc_has_cap_fixup_hcalls(void);
> bool kvmppc_has_cap_htm(void);
> bool kvmppc_has_cap_mmu_radix(void);
> bool kvmppc_has_cap_mmu_hash_v3(void);
> +int kvmppc_cap_smt_possible(void);
> int kvmppc_enable_hwrng(void);
> int kvmppc_put_books_sregs(PowerPCCPU *cpu);
> PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void);
> @@ -290,6 +291,11 @@ static inline bool kvmppc_has_cap_mmu_hash_v3(void)
> return false;
> }
>
> +static inline int kvmppc_cap_smt_possible(void)
> +{
> + return 0;
> +}
> +
> static inline int kvmppc_enable_hwrng(void)
> {
> return -1;
--
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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