> From: Igor Mammedov <imamm...@redhat.com>
> Sent: Tuesday, July 9, 2024 9:06 AM
> To: Salil Mehta <salil.me...@opnsrc.net>
>
> On Mon, 8 Jul 2024 23:30:01 +0000
> Salil Mehta <salil.me...@opnsrc.net> wrote:
>
> > Hi Igor,
> >
> > On 08/07/2024 13:32, Igor Mammedov wrote:
> > > On Sat, 6 Jul 2024 15:43:01 +0000
> > > Salil Mehta <salil.me...@opnsrc.net> wrote:
> > >
> > >> Hi Igor,
> > >> Thanks for taking out time to review.
> > >>
> > >> On Sat, Jul 6, 2024 at 1:12 PM Igor Mammedov
> <imamm...@redhat.com> wrote:
> > >>
> > >>> On Fri, 7 Jun 2024 12:56:42 +0100
> > >>> Salil Mehta <salil.me...@huawei.com> 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.me...@huawei.com>
> > >>>> Reviewed-by: Gavin Shan <gs...@redhat.com>
> > >>>> Tested-by: Vishnu Pajjuri <vis...@os.amperecomputing.com>
> > >>>> Reviewed-by: Jonathan Cameron <jonathan.came...@huawei.com>
> > >>>> Tested-by: Xianglai Li <lixiang...@loongson.cn>
> > >>>> Tested-by: Miguel Luis <miguel.l...@oracle.com>
> > >>>> Reviewed-by: Shaoqin Huang <shahu...@redhat.com>
> > >>>> Reviewed-by: Vishnu Pajjuri <vis...@os.amperecomputing.com>
> > >>>> Reviewed-by: Nicholas Piggin <npig...@gmail.com>
> > >>>> Tested-by: Zhao Liu <zhao1....@intel.com>
> > >>>> Reviewed-by: Zhao Liu <zhao1....@intel.com>
> > >>>> Reviewed-by: Harsh Prateek Bora <hars...@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;
> > >>>> +}
> > >>> Is there any reason why you are embedding/hiding kvm_state in new
> > >>> API instead of passing it as argument (all callers have it
> > >>> defined, so why not reuse that)?
> > >>>
> > >> It is a global variable and I don't think it is a usual practice to
> > >> specify the global variable as an input parameter.
> > > Ideally, global would be accessed once at API boundary entry and the
> > > passed as an argument to functions it calls.
> > > It makes it easier to follow as opposed to mixed access we have now,
> > > which is harder to review since one has to check both flavors
> > > (argument passed or directly accessed).
> > >
> > > in this patch kvm_init_vcpu() calls new kvm_create_vcpu() and the
> > > former caches these global into 's' local variable, so I'd reuse
> > > that local variable like kvm_get_vcpu() you are removing here did.
> > That is one perspective, but:
> > 1. kvm_create_vcpu() will also be called externally from other contexts.
>
> I'm fine with this as is, it would be better to mention in commit message
> that this (others) new API will be called externally. Otherwise it's not
> clear
> why KVMState is hidden inside.
ok, thanks.
Best regards
Salil.
> > It would be awkward to pass this variable from those non-local
> > places
> > where it would seem unnecessary.
> > 2. If you look at other symmetrical functions like kvm_destroy_vcpu(),
> > they also have a similar prototype.
> >
> > I think it is about doing a slight trade-off. If you really believe
> > this change is necessary for us to proceed, I will make the adjustment.
> > However, please note that it will affect the IBM team as well.
> >
> > Hi Nick,
> >
> > I hope you are okay with this suggested change?
> >
> > Thanks,
> > Salil
> > >>> otherwise patch lgtm
> > >>
> > >> May I request your Reviewed-by for this patch?
> > >>
> > >> Thanks
> > >> Salil.
> > >>
> > >>
> > >>>
> > >>>> +
> > >>>> 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[];
> > >>>
> >
>
