Re: [Qemu-devel] [PATCH 1/3] pseries: Support SMT systems for KVM Book3S-HV

[Alexander Graf]

On 29.09.2011, at 08:45, David Gibson wrote:

> Alex Graf has already made qemu support KVM for the pseries machine
> when using the Book3S-PR KVM variant (which runs the guest in
> usermode, emulating supervisor operations).  This code allows gets us
> very close to also working with KVM Book3S-HV (using the hypervisor
> capabilities of recent POWER CPUs).
> 
> This patch moves us another step towards Book3S-HV support by
> correctly handling SMT (multithreaded) POWER CPUs.  There are two
> parts to this:
> 
> * Querying KVM to check SMT capability, and if present, adjusting the
>   cpu numbers that qemu assigns to cause KVM to assign guest threads
>   to cores in the right way (this isn't automatic, because the POWER
>   HV support has a limitation that different threads on a single core
>   cannot be in different guests at the same time).
> 
> * Correctly informing the guest OS of the SMT thread to core mappings
>   via the device tree.
> 
> Signed-off-by: David Gibson <address@hidden>
> ---
> hw/spapr.c           |   23 ++++++++++++++++++++---
> target-ppc/helper.c  |   11 +++++++++++
> target-ppc/kvm.c     |   10 ++++++++++
> target-ppc/kvm_ppc.h |    6 ++++++
> 4 files changed, 47 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/spapr.c b/hw/spapr.c
> index b118975..ba9ae1c 100644
> --- a/hw/spapr.c
> +++ b/hw/spapr.c
> @@ -29,6 +29,9 @@
> #include "elf.h"
> #include "net.h"
> #include "blockdev.h"
> +#include "cpus.h"
> +#include "kvm.h"
> +#include "kvm_ppc.h"
> 
> #include "hw/boards.h"
> #include "hw/ppc.h"
> @@ -103,6 +106,7 @@ static void *spapr_create_fdt_skel(const char *cpu_model,
>     uint32_t interrupt_server_ranges_prop[] = {0, cpu_to_be32(smp_cpus)};
>     int i;
>     char *modelname;
> +    int smt = kvmppc_smt_threads();
> 
> #define _FDT(exp) \
>     do { \
> @@ -162,13 +166,17 @@ static void *spapr_create_fdt_skel(const char 
> *cpu_model,
> 
>     for (env = first_cpu; env != NULL; env = env->next_cpu) {
>         int index = env->cpu_index;
> -        uint32_t gserver_prop[] = {cpu_to_be32(index), 0}; /* HACK! */
> +        uint32_t servers_prop[smp_threads];
> +        uint32_t gservers_prop[smp_threads * 2];
>         char *nodename;
>         uint32_t segs[] = {cpu_to_be32(28), cpu_to_be32(40),
>                            0xffffffff, 0xffffffff};
>         uint32_t tbfreq = kvm_enabled() ? kvmppc_get_tbfreq() : TIMEBASE_FREQ;
>         uint32_t cpufreq = kvm_enabled() ? kvmppc_get_clockfreq() : 
> 1000000000;
> 
> +        if ((index % smt) != 0)
> +            continue;

Please run through checkpatch.pl

Alex