Re: [PATCH V13 1/8] accel/kvm: Extract common KVM vCPU {creation,parking} code

["Nicholas Piggin" <npiggin@gmail.com>]

Looks like there is a bit of noise around this recently. Do we
think the hotplug patches can get over the line this time?

If not, perhaps we work with Salil to get this patch 1 upstream
at least.

Thanks,
Nick

On Tue Jun 25, 2024 at 3:08 PM AEST, Harsh Prateek Bora wrote:
> +qemu-devel, qemu-ppc
>
> Ping!
>
> On 6/17/24 15:18, Harsh Prateek Bora wrote:
> > 
> > + MST, Igor - to help with early review/merge. TIA.
> > 
> > On 6/14/24 16:06, Salil Mehta wrote:
> >> Hello
> >>
> >>>   From: Harsh Prateek Bora <harshpb@linux.ibm.com>
> >>>   Sent: Friday, June 14, 2024 6:24 AM
> >>>   Hi Paolo, Nick,
> >>>   Can this patch 1/8 be merged earlier provided we have got 
> >>> sufficient R-bys
> >>>   for it and the review of entire series may take a longer time?
> >>>   We have some ppc64 patches based on it, hence the ask.
> >>>   Hi Salil,
> >>>   I am hoping we are not expecting anymore changes to this patch, please
> >>>   confirm.
> >>
> >>
> >> I do not expect any change. I had requested Michael to merge the complete
> >> series as it is stranding other users. He then requested Igor to take 
> >> a final look but
> >> he has not reverted yet. I'll remind Michael again. BTW, can you reply 
> >> to below
> >> patch explicitly indicating your interest in the series so that MST 
> >> knows who else
> >> are the stake holders here
> >>
> >> https://lore.kernel.org/qemu-devel/20240605160327.3c71f4ab@imammedo.users.ipa.redhat.com/
> >>
> >>
> >> Hi Paolo,
> >>
> >> A request, would it be possible to skim through this series from KVM 
> >> perspective?
> >> (although nothing has changed which will affect the KVM and this is 
> >> architecture
> >> agnostic patch-set)
> >>
> >> Many thanks!
> >>
> >> Best
> >> Salil.
> >>
> >>
> >>>   regards,
> >>>   Harsh
> >>>   On 6/7/24 17:26, Salil Mehta wrote:
> >>>   > KVM vCPU creation is done once during the vCPU realization when Qemu
> >>>   > vCPU thread is spawned. This is common to all the architectures 
> >>> as of now.
> >>>   >
> >>>   > Hot-unplug of vCPU results in destruction of the vCPU object in QOM
> >>>   > but the corresponding KVM vCPU object in the Host KVM is not 
> >>> destroyed
> >>>   > as KVM doesn't support vCPU removal. Therefore, its 
> >>> representative KVM
> >>>   > vCPU object/context in Qemu is parked.
> >>>   >
> >>>   > Refactor architecture common logic so that some APIs could be reused
> >>>   > by vCPU Hotplug code of some architectures likes ARM, Loongson etc.
> >>>   > Update new/old APIs with trace events. No functional change is 
> >>> intended
> >>>   here.
> >>>   >
> >>>   > Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> >>>   > Reviewed-by: Gavin Shan <gshan@redhat.com>
> >>>   > Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
> >>>   > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> >>>   > Tested-by: Xianglai Li <lixianglai@loongson.cn>
> >>>   > Tested-by: Miguel Luis <miguel.luis@oracle.com>
> >>>   > Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
> >>>   > Reviewed-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
> >>>   > Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> >>>   > Tested-by: Zhao Liu <zhao1.liu@intel.com>
> >>>   > Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
> >>>   > Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
> >>>   > ---
> >>>   >   accel/kvm/kvm-all.c    | 95 
> >>> ++++++++++++++++++++++++++++------------
> >>>   --
> >>>   >   accel/kvm/kvm-cpus.h   |  1 -
> >>>   >   accel/kvm/trace-events |  5 ++-
> >>>   >   include/sysemu/kvm.h   | 25 +++++++++++
> >>>   >   4 files changed, 92 insertions(+), 34 deletions(-)
> >>>   >
> >>>   > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index
> >>>   > c0be9f5eed..8f9128bb92 100644
> >>>   > --- a/accel/kvm/kvm-all.c
> >>>   > +++ b/accel/kvm/kvm-all.c
> >>>   > @@ -340,14 +340,71 @@ err:
> >>>   >       return ret;
> >>>   >   }
> >>>   >
> >>>   > +void kvm_park_vcpu(CPUState *cpu)
> >>>   > +{
> >>>   > +    struct KVMParkedVcpu *vcpu;
> >>>   > +
> >>>   > +    trace_kvm_park_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
> >>>   > +
> >>>   > +    vcpu = g_malloc0(sizeof(*vcpu));
> >>>   > +    vcpu->vcpu_id = kvm_arch_vcpu_id(cpu);
> >>>   > +    vcpu->kvm_fd = cpu->kvm_fd;
> >>>   > +    QLIST_INSERT_HEAD(&kvm_state->kvm_parked_vcpus, vcpu, node); }
> >>>   > +
> >>>   > +int kvm_unpark_vcpu(KVMState *s, unsigned long vcpu_id) {
> >>>   > +    struct KVMParkedVcpu *cpu;
> >>>   > +    int kvm_fd = -ENOENT;
> >>>   > +
> >>>   > +    QLIST_FOREACH(cpu, &s->kvm_parked_vcpus, node) {
> >>>   > +        if (cpu->vcpu_id == vcpu_id) {
> >>>   > +            QLIST_REMOVE(cpu, node);
> >>>   > +            kvm_fd = cpu->kvm_fd;
> >>>   > +            g_free(cpu);
> >>>   > +        }
> >>>   > +    }
> >>>   > +
> >>>   > +    trace_kvm_unpark_vcpu(vcpu_id, kvm_fd > 0 ? "unparked" : "not
> >>>   > + found parked");
> >>>   > +
> >>>   > +    return kvm_fd;
> >>>   > +}
> >>>   > +
> >>>   > +int kvm_create_vcpu(CPUState *cpu)
> >>>   > +{
> >>>   > +    unsigned long vcpu_id = kvm_arch_vcpu_id(cpu);
> >>>   > +    KVMState *s = kvm_state;
> >>>   > +    int kvm_fd;
> >>>   > +
> >>>   > +    /* check if the KVM vCPU already exist but is parked */
> >>>   > +    kvm_fd = kvm_unpark_vcpu(s, vcpu_id);
> >>>   > +    if (kvm_fd < 0) {
> >>>   > +        /* vCPU not parked: create a new KVM vCPU */
> >>>   > +        kvm_fd = kvm_vm_ioctl(s, KVM_CREATE_VCPU, vcpu_id);
> >>>   > +        if (kvm_fd < 0) {
> >>>   > +            error_report("KVM_CREATE_VCPU IOCTL failed for vCPU 
> >>> %lu",
> >>>   vcpu_id);
> >>>   > +            return kvm_fd;
> >>>   > +        }
> >>>   > +    }
> >>>   > +
> >>>   > +    cpu->kvm_fd = kvm_fd;
> >>>   > +    cpu->kvm_state = s;
> >>>   > +    cpu->vcpu_dirty = true;
> >>>   > +    cpu->dirty_pages = 0;
> >>>   > +    cpu->throttle_us_per_full = 0;
> >>>   > +
> >>>   > +    trace_kvm_create_vcpu(cpu->cpu_index, vcpu_id, kvm_fd);
> >>>   > +
> >>>   > +    return 0;
> >>>   > +}
> >>>   > +
> >>>   >   static int do_kvm_destroy_vcpu(CPUState *cpu)
> >>>   >   {
> >>>   >       KVMState *s = kvm_state;
> >>>   >       long mmap_size;
> >>>   > -    struct KVMParkedVcpu *vcpu = NULL;
> >>>   >       int ret = 0;
> >>>   >
> >>>   > -    trace_kvm_destroy_vcpu();
> >>>   > +    trace_kvm_destroy_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
> >>>   >
> >>>   >       ret = kvm_arch_destroy_vcpu(cpu);
> >>>   >       if (ret < 0) {
> >>>   > @@ -373,10 +430,7 @@ static int do_kvm_destroy_vcpu(CPUState *cpu)
> >>>   >           }
> >>>   >       }
> >>>   >
> >>>   > -    vcpu = g_malloc0(sizeof(*vcpu));
> >>>   > -    vcpu->vcpu_id = kvm_arch_vcpu_id(cpu);
> >>>   > -    vcpu->kvm_fd = cpu->kvm_fd;
> >>>   > -    QLIST_INSERT_HEAD(&kvm_state->kvm_parked_vcpus, vcpu, node);
> >>>   > +    kvm_park_vcpu(cpu);
> >>>   >   err:
> >>>   >       return ret;
> >>>   >   }
> >>>   > @@ -389,24 +443,6 @@ void kvm_destroy_vcpu(CPUState *cpu)
> >>>   >       }
> >>>   >   }
> >>>   >
> >>>   > -static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id) -{
> >>>   > -    struct KVMParkedVcpu *cpu;
> >>>   > -
> >>>   > -    QLIST_FOREACH(cpu, &s->kvm_parked_vcpus, node) {
> >>>   > -        if (cpu->vcpu_id == vcpu_id) {
> >>>   > -            int kvm_fd;
> >>>   > -
> >>>   > -            QLIST_REMOVE(cpu, node);
> >>>   > -            kvm_fd = cpu->kvm_fd;
> >>>   > -            g_free(cpu);
> >>>   > -            return kvm_fd;
> >>>   > -        }
> >>>   > -    }
> >>>   > -
> >>>   > -    return kvm_vm_ioctl(s, KVM_CREATE_VCPU, (void *)vcpu_id);
> >>>   > -}
> >>>   > -
> >>>   >   int kvm_init_vcpu(CPUState *cpu, Error **errp)
> >>>   >   {
> >>>   >       KVMState *s = kvm_state;
> >>>   > @@ -415,19 +451,14 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)
> >>>   >
> >>>   >       trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
> >>>   >
> >>>   > -    ret = kvm_get_vcpu(s, kvm_arch_vcpu_id(cpu));
> >>>   > +    ret = kvm_create_vcpu(cpu);
> >>>   >       if (ret < 0) {
> >>>   > -        error_setg_errno(errp, -ret, "kvm_init_vcpu: 
> >>> kvm_get_vcpu failed
> >>>   (%lu)",
> >>>   > +        error_setg_errno(errp, -ret,
> >>>   > +                         "kvm_init_vcpu: kvm_create_vcpu failed
> >>>   > + (%lu)",
> >>>   >                            kvm_arch_vcpu_id(cpu));
> >>>   >           goto err;
> >>>   >       }
> >>>   >
> >>>   > -    cpu->kvm_fd = ret;
> >>>   > -    cpu->kvm_state = s;
> >>>   > -    cpu->vcpu_dirty = true;
> >>>   > -    cpu->dirty_pages = 0;
> >>>   > -    cpu->throttle_us_per_full = 0;
> >>>   > -
> >>>   >       mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0);
> >>>   >       if (mmap_size < 0) {
> >>>   >           ret = mmap_size;
> >>>   > diff --git a/accel/kvm/kvm-cpus.h b/accel/kvm/kvm-cpus.h index
> >>>   > ca40add32c..171b22fd29 100644
> >>>   > --- a/accel/kvm/kvm-cpus.h
> >>>   > +++ b/accel/kvm/kvm-cpus.h
> >>>   > @@ -22,5 +22,4 @@ bool kvm_supports_guest_debug(void);
> >>>   >   int kvm_insert_breakpoint(CPUState *cpu, int type, vaddr addr, 
> >>> vaddr
> >>>   len);
> >>>   >   int kvm_remove_breakpoint(CPUState *cpu, int type, vaddr addr, 
> >>> vaddr
> >>>   len);
> >>>   >   void kvm_remove_all_breakpoints(CPUState *cpu);
> >>>   > -
> >>>   >   #endif /* KVM_CPUS_H */
> >>>   > diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events index
> >>>   > 681ccb667d..37626c1ac5 100644
> >>>   > --- a/accel/kvm/trace-events
> >>>   > +++ b/accel/kvm/trace-events
> >>>   > @@ -9,6 +9,10 @@ kvm_device_ioctl(int fd, int type, void *arg) 
> >>> "dev fd
> >>>   %d, type 0x%x, arg %p"
> >>>   >   kvm_failed_reg_get(uint64_t id, const char *msg) "Warning: 
> >>> Unable to
> >>>   retrieve ONEREG %" PRIu64 " from KVM: %s"
> >>>   >   kvm_failed_reg_set(uint64_t id, const char *msg) "Warning: 
> >>> Unable to
> >>>   set ONEREG %" PRIu64 " to KVM: %s"
> >>>   >   kvm_init_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: 
> >>> %d id:
> >>>   %lu"
> >>>   > +kvm_create_vcpu(int cpu_index, unsigned long arch_cpu_id, int
> >>>   kvm_fd) "index: %d, id: %lu, kvm fd: %d"
> >>>   > +kvm_destroy_vcpu(int cpu_index, unsigned long arch_cpu_id) "index:
> >>>   %d id: %lu"
> >>>   > +kvm_park_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d
> >>>   id: %lu"
> >>>   > +kvm_unpark_vcpu(unsigned long arch_cpu_id, const char *msg) "id: 
> >>> %lu
> >>>   %s"
> >>>   >   kvm_irqchip_commit_routes(void) ""
> >>>   >   kvm_irqchip_add_msi_route(char *name, int vector, int virq) 
> >>> "dev %s
> >>>   vector %d virq %d"
> >>>   >   kvm_irqchip_update_msi_route(int virq) "Updating MSI route 
> >>> virq=%d"
> >>>   > @@ -25,7 +29,6 @@ kvm_dirty_ring_reaper(const char *s) "%s"
> >>>   >   kvm_dirty_ring_reap(uint64_t count, int64_t t) "reaped 
> >>> %"PRIu64" pages
> >>>   (took %"PRIi64" us)"
> >>>   >   kvm_dirty_ring_reaper_kick(const char *reason) "%s"
> >>>   >   kvm_dirty_ring_flush(int finished) "%d"
> >>>   > -kvm_destroy_vcpu(void) ""
> >>>   >   kvm_failed_get_vcpu_mmap_size(void) ""
> >>>   >   kvm_cpu_exec(void) ""
> >>>   >   kvm_interrupt_exit_request(void) ""
> >>>   > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h index
> >>>   > c31d9c7356..c4a914b3d8 100644
> >>>   > --- a/include/sysemu/kvm.h
> >>>   > +++ b/include/sysemu/kvm.h
> >>>   > @@ -313,6 +313,31 @@ int kvm_create_device(KVMState *s, uint64_t
> >>>   type, bool test);
> >>>   >    */
> >>>   >   bool kvm_device_supported(int vmfd, uint64_t type);
> >>>   >
> >>>   > +/**
> >>>   > + * kvm_create_vcpu - Gets a parked KVM vCPU or creates a KVM vCPU
> >>>   > + * @cpu: QOM CPUState object for which KVM vCPU has to be
> >>>   fetched/created.
> >>>   > + *
> >>>   > + * @returns: 0 when success, errno (<0) when failed.
> >>>   > + */
> >>>   > +int kvm_create_vcpu(CPUState *cpu);
> >>>   > +
> >>>   > +/**
> >>>   > + * kvm_park_vcpu - Park QEMU KVM vCPU context
> >>>   > + * @cpu: QOM CPUState object for which QEMU KVM vCPU context has
> >>>   to be parked.
> >>>   > + *
> >>>   > + * @returns: none
> >>>   > + */
> >>>   > +void kvm_park_vcpu(CPUState *cpu);
> >>>   > +
> >>>   > +/**
> >>>   > + * kvm_unpark_vcpu - unpark QEMU KVM vCPU context
> >>>   > + * @s: KVM State
> >>>   > + * @vcpu_id: Architecture vCPU ID of the parked vCPU
> >>>   > + *
> >>>   > + * @returns: KVM fd
> >>>   > + */
> >>>   > +int kvm_unpark_vcpu(KVMState *s, unsigned long vcpu_id);
> >>>   > +
> >>>   >   /* Arch specific hooks */
> >>>   >
> >>>   >   extern const KVMCapabilityInfo kvm_arch_required_capabilities[];