[PATCH v4 0/6] Improve KVM's interaction with CPU hotplug

[PATCH v4 0/6] Improve KVM's interaction with CPU hotplug

[Chao Gao]

Changes from v3->v4:
 - rebased to the lastest kvm/next branch.
 - add Sean's reviewed-by tags
 - add Marc's patch to simplify ARM's cpu hotplug logic in KVM

Changes from v2->v3:
 - rebased to the latest kvm/next branch. 
 - patch 1: rename {svm,vmx}_check_processor_compat to follow the name
	    convention
 - patch 3: newly added to provide more information when hardware enabling
	    fails
 - patch 4: reset hardware_enable_failed if hardware enabling fails. And
	    remove redundent kernel log.
 - patch 5: add a pr_err() for setup_vmcs_config() path.

Changes from v1->v2: (all comments/suggestions on v1 are from Sean, thanks)
 - Merged v1's patch 2 into patch 1, and v1's patch 5 into patch 6.
 - Use static_call for check_processor_compatibility().
 - Generate patch 2 with "git revert" and do manual changes based on that.
 - Loosen the WARN_ON() in kvm_arch_check_processor_compat() instead of
   removing it.
 - KVM always prevent incompatible CPUs from being brought up regardless of
   running VMs.
 - Use pr_warn instead of pr_info to emit logs when KVM finds offending
   CPUs.

KVM registers its CPU hotplug callback to CPU starting section. And in the
callback, KVM enables hardware virtualization on hotplugged CPUs if any VM
is running on existing CPUs.

There are two problems in the process:
1. KVM doesn't do compatibility checks before enabling hardware
virtualization on hotplugged CPUs. This may cause #GP if VMX isn't
supported or vmentry failure if some in-use VMX features are missing on
hotplugged CPUs. Both break running VMs.
2. Callbacks in CPU STARTING section cannot fail. So, even if KVM finds
some incompatible CPUs, its callback cannot block CPU hotplug.

This series improves KVM's interaction with CPU hotplug to avoid
incompatible CPUs breaking running VMs. Following changes are made:

1. move KVM's CPU hotplug callback to ONLINE section (suggested by Thomas)
2. do compatibility checks on hotplugged CPUs.
3. abort onlining incompatible CPUs

This series is a follow-up to the discussion about KVM and CPU hotplug
https://lore.kernel.org/lkml/3d3296f0-9245-40f9-1b5a-efffdb082de9@redhat.com/T/

Note: this series is tested only on Intel systems.

Chao Gao (4):
  KVM: x86: Move check_processor_compatibility from init ops to runtime
    ops
  Partially revert "KVM: Pass kvm_init()'s opaque param to additional
    arch funcs"
  KVM: Rename and move CPUHP_AP_KVM_STARTING to ONLINE section
  KVM: Do compatibility checks on hotplugged CPUs

Marc Zyngier (1):
  KVM: arm64: Simplify the CPUHP logic

Sean Christopherson (1):
  KVM: Provide more information in kernel log if hardware enabling fails

 arch/arm64/kvm/arch_timer.c        | 27 ++++-------
 arch/arm64/kvm/arm.c               |  6 ++-
 arch/arm64/kvm/vgic/vgic-init.c    | 19 +-------
 arch/mips/kvm/mips.c               |  2 +-
 arch/powerpc/kvm/powerpc.c         |  2 +-
 arch/riscv/kvm/main.c              |  2 +-
 arch/s390/kvm/kvm-s390.c           |  2 +-
 arch/x86/include/asm/kvm-x86-ops.h |  1 +
 arch/x86/include/asm/kvm_host.h    |  2 +-
 arch/x86/kvm/svm/svm.c             |  4 +-
 arch/x86/kvm/vmx/evmcs.c           |  2 +-
 arch/x86/kvm/vmx/evmcs.h           |  2 +-
 arch/x86/kvm/vmx/vmx.c             | 22 +++++----
 arch/x86/kvm/x86.c                 | 16 +++++--
 include/kvm/arm_arch_timer.h       |  4 ++
 include/kvm/arm_vgic.h             |  4 ++
 include/linux/cpuhotplug.h         |  5 +-
 include/linux/kvm_host.h           |  2 +-
 virt/kvm/kvm_main.c                | 73 +++++++++++++++++++-----------
 19 files changed, 107 insertions(+), 90 deletions(-)

-- 
2.25.1

[PATCH v4 2/6] Partially revert "KVM: Pass kvm_init()'s opaque param to additional arch funcs"

[Chao Gao]

This partially reverts commit b99040853738 ("KVM: Pass kvm_init()'s opaque
param to additional arch funcs") remove opaque from
kvm_arch_check_processor_compat because no one uses this opaque now.
Address conflicts for ARM (due to file movement) and manually handle RISC-V
which comes after the commit.

And changes about kvm_arch_hardware_setup() in original commit are still
needed so they are not reverted.

Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
---
 arch/arm64/kvm/arm.c       |  2 +-
 arch/mips/kvm/mips.c       |  2 +-
 arch/powerpc/kvm/powerpc.c |  2 +-
 arch/riscv/kvm/main.c      |  2 +-
 arch/s390/kvm/kvm-s390.c   |  2 +-
 arch/x86/kvm/x86.c         |  2 +-
 include/linux/kvm_host.h   |  2 +-
 virt/kvm/kvm_main.c        | 16 +++-------------
 8 files changed, 10 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index ecc5958e27fe..0165cf3aac3a 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -73,7 +73,7 @@ int kvm_arch_hardware_setup(void *opaque)
 	return 0;
 }
 
-int kvm_arch_check_processor_compat(void *opaque)
+int kvm_arch_check_processor_compat(void)
 {
 	return 0;
 }
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index a25e0b73ee70..092d09fb6a7e 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -140,7 +140,7 @@ int kvm_arch_hardware_setup(void *opaque)
 	return 0;
 }
 
-int kvm_arch_check_processor_compat(void *opaque)
+int kvm_arch_check_processor_compat(void)
 {
 	return 0;
 }
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 2ad0ccd202d5..30c817f3fa0c 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -423,7 +423,7 @@ int kvm_arch_hardware_setup(void *opaque)
 	return 0;
 }
 
-int kvm_arch_check_processor_compat(void *opaque)
+int kvm_arch_check_processor_compat(void)
 {
 	return kvmppc_core_check_processor_compat();
 }
diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
index 2e5ca43c8c49..992877e78393 100644
--- a/arch/riscv/kvm/main.c
+++ b/arch/riscv/kvm/main.c
@@ -20,7 +20,7 @@ long kvm_arch_dev_ioctl(struct file *filp,
 	return -EINVAL;
 }
 
-int kvm_arch_check_processor_compat(void *opaque)
+int kvm_arch_check_processor_compat(void)
 {
 	return 0;
 }
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 577f1ead6a51..0053b81c6b02 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -252,7 +252,7 @@ int kvm_arch_hardware_enable(void)
 	return 0;
 }
 
-int kvm_arch_check_processor_compat(void *opaque)
+int kvm_arch_check_processor_compat(void)
 {
 	return 0;
 }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9b484ed61f37..ffb88f0b7265 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11509,7 +11509,7 @@ void kvm_arch_hardware_unsetup(void)
 	static_call(kvm_x86_hardware_unsetup)();
 }
 
-int kvm_arch_check_processor_compat(void *opaque)
+int kvm_arch_check_processor_compat(void)
 {
 	struct cpuinfo_x86 *c = &cpu_data(smp_processor_id());
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f11039944c08..2ad78e729bf7 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1413,7 +1413,7 @@ int kvm_arch_hardware_enable(void);
 void kvm_arch_hardware_disable(void);
 int kvm_arch_hardware_setup(void *opaque);
 void kvm_arch_hardware_unsetup(void);
-int kvm_arch_check_processor_compat(void *opaque);
+int kvm_arch_check_processor_compat(void);
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
 bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 83c57bcc6eb6..ee47d33d69e1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5643,22 +5643,14 @@ void kvm_unregister_perf_callbacks(void)
 }
 #endif
 
-struct kvm_cpu_compat_check {
-	void *opaque;
-	int *ret;
-};
-
-static void check_processor_compat(void *data)
+static void check_processor_compat(void *rtn)
 {
-	struct kvm_cpu_compat_check *c = data;
-
-	*c->ret = kvm_arch_check_processor_compat(c->opaque);
+	*(int *)rtn = kvm_arch_check_processor_compat();
 }
 
 int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
 		  struct module *module)
 {
-	struct kvm_cpu_compat_check c;
 	int r;
 	int cpu;
 
@@ -5686,10 +5678,8 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
 	if (r < 0)
 		goto out_free_1;
 
-	c.ret = &r;
-	c.opaque = opaque;
 	for_each_online_cpu(cpu) {
-		smp_call_function_single(cpu, check_processor_compat, &c, 1);
+		smp_call_function_single(cpu, check_processor_compat, &r, 1);
 		if (r < 0)
 			goto out_free_2;
 	}
-- 
2.25.1

Re: [PATCH v4 2/6] Partially revert "KVM: Pass kvm_init()'s opaque param to additional arch funcs"

[Anup Patel]

On Wed, Feb 16, 2022 at 8:46 AM Chao Gao <chao.gao@intel.com> wrote:
>
> This partially reverts commit b99040853738 ("KVM: Pass kvm_init()'s opaque
> param to additional arch funcs") remove opaque from
> kvm_arch_check_processor_compat because no one uses this opaque now.
> Address conflicts for ARM (due to file movement) and manually handle RISC-V
> which comes after the commit.
>
> And changes about kvm_arch_hardware_setup() in original commit are still
> needed so they are not reverted.
>
> Signed-off-by: Chao Gao <chao.gao@intel.com>
> Reviewed-by: Sean Christopherson <seanjc@google.com>

For KVM RISC-V:
Acked-by: Anup Patel <anup@brainfault.org>

Regards,
Anup


> ---
>  arch/arm64/kvm/arm.c       |  2 +-
>  arch/mips/kvm/mips.c       |  2 +-
>  arch/powerpc/kvm/powerpc.c |  2 +-
>  arch/riscv/kvm/main.c      |  2 +-
>  arch/s390/kvm/kvm-s390.c   |  2 +-
>  arch/x86/kvm/x86.c         |  2 +-
>  include/linux/kvm_host.h   |  2 +-
>  virt/kvm/kvm_main.c        | 16 +++-------------
>  8 files changed, 10 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index ecc5958e27fe..0165cf3aac3a 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -73,7 +73,7 @@ int kvm_arch_hardware_setup(void *opaque)
>         return 0;
>  }
>
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>         return 0;
>  }
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index a25e0b73ee70..092d09fb6a7e 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -140,7 +140,7 @@ int kvm_arch_hardware_setup(void *opaque)
>         return 0;
>  }
>
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>         return 0;
>  }
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 2ad0ccd202d5..30c817f3fa0c 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -423,7 +423,7 @@ int kvm_arch_hardware_setup(void *opaque)
>         return 0;
>  }
>
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>         return kvmppc_core_check_processor_compat();
>  }
> diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
> index 2e5ca43c8c49..992877e78393 100644
> --- a/arch/riscv/kvm/main.c
> +++ b/arch/riscv/kvm/main.c
> @@ -20,7 +20,7 @@ long kvm_arch_dev_ioctl(struct file *filp,
>         return -EINVAL;
>  }
>
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>         return 0;
>  }
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 577f1ead6a51..0053b81c6b02 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -252,7 +252,7 @@ int kvm_arch_hardware_enable(void)
>         return 0;
>  }
>
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>         return 0;
>  }
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9b484ed61f37..ffb88f0b7265 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -11509,7 +11509,7 @@ void kvm_arch_hardware_unsetup(void)
>         static_call(kvm_x86_hardware_unsetup)();
>  }
>
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>         struct cpuinfo_x86 *c = &cpu_data(smp_processor_id());
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index f11039944c08..2ad78e729bf7 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1413,7 +1413,7 @@ int kvm_arch_hardware_enable(void);
>  void kvm_arch_hardware_disable(void);
>  int kvm_arch_hardware_setup(void *opaque);
>  void kvm_arch_hardware_unsetup(void);
> -int kvm_arch_check_processor_compat(void *opaque);
> +int kvm_arch_check_processor_compat(void);
>  int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
>  bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 83c57bcc6eb6..ee47d33d69e1 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -5643,22 +5643,14 @@ void kvm_unregister_perf_callbacks(void)
>  }
>  #endif
>
> -struct kvm_cpu_compat_check {
> -       void *opaque;
> -       int *ret;
> -};
> -
> -static void check_processor_compat(void *data)
> +static void check_processor_compat(void *rtn)
>  {
> -       struct kvm_cpu_compat_check *c = data;
> -
> -       *c->ret = kvm_arch_check_processor_compat(c->opaque);
> +       *(int *)rtn = kvm_arch_check_processor_compat();
>  }
>
>  int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
>                   struct module *module)
>  {
> -       struct kvm_cpu_compat_check c;
>         int r;
>         int cpu;
>
> @@ -5686,10 +5678,8 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
>         if (r < 0)
>                 goto out_free_1;
>
> -       c.ret = &r;
> -       c.opaque = opaque;
>         for_each_online_cpu(cpu) {
> -               smp_call_function_single(cpu, check_processor_compat, &c, 1);
> +               smp_call_function_single(cpu, check_processor_compat, &r, 1);
>                 if (r < 0)
>                         goto out_free_2;
>         }
> --
> 2.25.1
>

Re: [PATCH v4 2/6] Partially revert "KVM: Pass kvm_init()'s opaque param to additional arch funcs"

[Claudio Imbrenda]

On Wed, 16 Feb 2022 11:15:17 +0800
Chao Gao <chao.gao@intel.com> wrote:

> This partially reverts commit b99040853738 ("KVM: Pass kvm_init()'s opaque
> param to additional arch funcs") remove opaque from
> kvm_arch_check_processor_compat because no one uses this opaque now.
> Address conflicts for ARM (due to file movement) and manually handle RISC-V
> which comes after the commit.
> 
> And changes about kvm_arch_hardware_setup() in original commit are still
> needed so they are not reverted.
> 
> Signed-off-by: Chao Gao <chao.gao@intel.com>
> Reviewed-by: Sean Christopherson <seanjc@google.com>

for KVM s390:

Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  arch/arm64/kvm/arm.c       |  2 +-
>  arch/mips/kvm/mips.c       |  2 +-
>  arch/powerpc/kvm/powerpc.c |  2 +-
>  arch/riscv/kvm/main.c      |  2 +-
>  arch/s390/kvm/kvm-s390.c   |  2 +-
>  arch/x86/kvm/x86.c         |  2 +-
>  include/linux/kvm_host.h   |  2 +-
>  virt/kvm/kvm_main.c        | 16 +++-------------
>  8 files changed, 10 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index ecc5958e27fe..0165cf3aac3a 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -73,7 +73,7 @@ int kvm_arch_hardware_setup(void *opaque)
>  	return 0;
>  }
>  
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>  	return 0;
>  }
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index a25e0b73ee70..092d09fb6a7e 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -140,7 +140,7 @@ int kvm_arch_hardware_setup(void *opaque)
>  	return 0;
>  }
>  
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>  	return 0;
>  }
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 2ad0ccd202d5..30c817f3fa0c 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -423,7 +423,7 @@ int kvm_arch_hardware_setup(void *opaque)
>  	return 0;
>  }
>  
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>  	return kvmppc_core_check_processor_compat();
>  }
> diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
> index 2e5ca43c8c49..992877e78393 100644
> --- a/arch/riscv/kvm/main.c
> +++ b/arch/riscv/kvm/main.c
> @@ -20,7 +20,7 @@ long kvm_arch_dev_ioctl(struct file *filp,
>  	return -EINVAL;
>  }
>  
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>  	return 0;
>  }
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 577f1ead6a51..0053b81c6b02 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -252,7 +252,7 @@ int kvm_arch_hardware_enable(void)
>  	return 0;
>  }
>  
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>  	return 0;
>  }
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9b484ed61f37..ffb88f0b7265 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -11509,7 +11509,7 @@ void kvm_arch_hardware_unsetup(void)
>  	static_call(kvm_x86_hardware_unsetup)();
>  }
>  
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>  {
>  	struct cpuinfo_x86 *c = &cpu_data(smp_processor_id());
>  
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index f11039944c08..2ad78e729bf7 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1413,7 +1413,7 @@ int kvm_arch_hardware_enable(void);
>  void kvm_arch_hardware_disable(void);
>  int kvm_arch_hardware_setup(void *opaque);
>  void kvm_arch_hardware_unsetup(void);
> -int kvm_arch_check_processor_compat(void *opaque);
> +int kvm_arch_check_processor_compat(void);
>  int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
>  bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 83c57bcc6eb6..ee47d33d69e1 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -5643,22 +5643,14 @@ void kvm_unregister_perf_callbacks(void)
>  }
>  #endif
>  
> -struct kvm_cpu_compat_check {
> -	void *opaque;
> -	int *ret;
> -};
> -
> -static void check_processor_compat(void *data)
> +static void check_processor_compat(void *rtn)
>  {
> -	struct kvm_cpu_compat_check *c = data;
> -
> -	*c->ret = kvm_arch_check_processor_compat(c->opaque);
> +	*(int *)rtn = kvm_arch_check_processor_compat();
>  }
>  
>  int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
>  		  struct module *module)
>  {
> -	struct kvm_cpu_compat_check c;
>  	int r;
>  	int cpu;
>  
> @@ -5686,10 +5678,8 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
>  	if (r < 0)
>  		goto out_free_1;
>  
> -	c.ret = &r;
> -	c.opaque = opaque;
>  	for_each_online_cpu(cpu) {
> -		smp_call_function_single(cpu, check_processor_compat, &c, 1);
> +		smp_call_function_single(cpu, check_processor_compat, &r, 1);
>  		if (r < 0)
>  			goto out_free_2;
>  	}

Re: [PATCH v4 0/6] Improve KVM's interaction with CPU hotplug

[Chao Gao]

Ping. Anyone can help to review this series (particularly patch 3-5)?

FYI, Sean gave his Reviewed-by to patch 1,2,5 and 6.

Re: [PATCH v4 2/6] Partially revert "KVM: Pass kvm_init()'s opaque param to additional arch funcs"

[Suzuki Kuruppassery Poulose]

On 16/02/2022 03:15, Chao Gao wrote:
> This partially reverts commit b99040853738 ("KVM: Pass kvm_init()'s opaque
> param to additional arch funcs") remove opaque from
> kvm_arch_check_processor_compat because no one uses this opaque now.
> Address conflicts for ARM (due to file movement) and manually handle RISC-V
> which comes after the commit.
> 
> And changes about kvm_arch_hardware_setup() in original commit are still
> needed so they are not reverted.
> 
> Signed-off-by: Chao Gao <chao.gao@intel.com>
> Reviewed-by: Sean Christopherson <seanjc@google.com>
> ---
>   arch/arm64/kvm/arm.c       |  2 +-
>   arch/mips/kvm/mips.c       |  2 +-
>   arch/powerpc/kvm/powerpc.c |  2 +-
>   arch/riscv/kvm/main.c      |  2 +-
>   arch/s390/kvm/kvm-s390.c   |  2 +-
>   arch/x86/kvm/x86.c         |  2 +-
>   include/linux/kvm_host.h   |  2 +-
>   virt/kvm/kvm_main.c        | 16 +++-------------
>   8 files changed, 10 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index ecc5958e27fe..0165cf3aac3a 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -73,7 +73,7 @@ int kvm_arch_hardware_setup(void *opaque)
>   	return 0;
>   }
>   
> -int kvm_arch_check_processor_compat(void *opaque)
> +int kvm_arch_check_processor_compat(void)
>   {
>   	return 0;
>   }

For arm64 :

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>