Re: [PATCH] KVM: Directly return result from kvm_arch_check_processor_compat()

Paolo Bonzini
2019-05-20T13:43:48Z

On 20/04/19 07:18, Sean Christopherson wrote:
> Add a wrapper to invoke kvm_arch_check_processor_compat() so that the
> boilerplate ugliness of checking virtualization support on all CPUs is
> hidden from the arch specific code. x86's implementation in particular
> is quite heinous, as it unnecessarily propagates the out-param pattern
> into kvm_x86_ops.
>
> While the x86 specific issue could be resolved solely by changing
> kvm_x86_ops, make the change for all architectures as returning a value
> directly is prettier and technically more robust, e.g. s390 doesn't set
> the out param, which could lead to subtle breakage in the (highly
> unlikely) scenario where the out-param was not pre-initialized by the
> caller.
>
> Opportunistically annotate svm_check_processor_compat() with __init.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>
> Tested on VMX only.
>
> arch/mips/kvm/mips.c | 4 ++--
> arch/powerpc/kvm/powerpc.c | 4 ++--
> arch/s390/include/asm/kvm_host.h | 1 -
> arch/s390/kvm/kvm-s390.c | 5 +++++
> arch/x86/include/asm/kvm_host.h | 2 +-
> arch/x86/kvm/svm.c | 4 ++--
> arch/x86/kvm/vmx/vmx.c | 8 ++++----
> arch/x86/kvm/x86.c | 4 ++--
> include/linux/kvm_host.h | 2 +-
> virt/kvm/arm/arm.c | 4 ++--
> virt/kvm/kvm_main.c | 9 ++++++---
> 11 files changed, 27 insertions(+), 20 deletions(-)
>
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index 6d0517ac18e5..1c22b938c550 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -123,9 +123,9 @@ int kvm_arch_hardware_setup(void)
> return 0;
> }
>
> -void kvm_arch_check_processor_compat(void *rtn)
> +int kvm_arch_check_processor_compat(void)
> {
> - *(int *)rtn = 0;
> + return 0;
> }
>
> int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 92910b7c5bcc..7b7635201739 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -425,9 +425,9 @@ int kvm_arch_hardware_setup(void)
> return 0;
> }
>
> -void kvm_arch_check_processor_compat(void *rtn)
> +int kvm_arch_check_processor_compat(void)
> {
> - *(int *)rtn = kvmppc_core_check_processor_compat();
> + return kvmppc_core_check_processor_compat();
> }
>
> int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index c47e22bba87f..96a1603ecf10 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -903,7 +903,6 @@ extern int kvm_s390_gisc_register(struct kvm *kvm, u32 gisc);
> extern int kvm_s390_gisc_unregister(struct kvm *kvm, u32 gisc);
>
> static inline void kvm_arch_hardware_disable(void) {}
> -static inline void kvm_arch_check_processor_compat(void *rtn) {}
> static inline void kvm_arch_sync_events(struct kvm *kvm) {}
> static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
> static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 28f35d2b06cb..4c50bd533ebc 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -221,6 +221,11 @@ int kvm_arch_hardware_enable(void)
> return 0;
> }
>
> +int kvm_arch_check_processor_compat(void)
> +{
> + return 0;
> +}
> +
> static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
> unsigned long end);
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 8d68ba0cba0c..02ba99ef8c5f 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -995,7 +995,7 @@ struct kvm_x86_ops {
> int (*disabled_by_bios)(void); /* __init */
> int (*hardware_enable)(void);
> void (*hardware_disable)(void);
> - void (*check_processor_compatibility)(void *rtn);
> + int (*check_processor_compatibility)(void);/* __init */
> int (*hardware_setup)(void); /* __init */
> void (*hardware_unsetup)(void); /* __exit */
> bool (*cpu_has_accelerated_tpr)(void);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 406b558abfef..236e2fc0edec 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -5859,9 +5859,9 @@ svm_patch_hypercall(struct kvm_vcpu *vcpu, unsigned char *hypercall)
> hypercall[2] = 0xd9;
> }
>
> -static void svm_check_processor_compat(void *rtn)
> +static int __init svm_check_processor_compat(void)
> {
> - *(int *)rtn = 0;
> + return 0;
> }
>
> static bool svm_cpu_has_accelerated_tpr(void)
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d8f101b58ab8..7d0733b8f383 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6720,22 +6720,22 @@ static int vmx_vm_init(struct kvm *kvm)
> return 0;
> }
>
> -static void __init vmx_check_processor_compat(void *rtn)
> +static int __init vmx_check_processor_compat(void)
> {
> struct vmcs_config vmcs_conf;
> struct vmx_capability vmx_cap;
>
> - *(int *)rtn = 0;
> if (setup_vmcs_config(&vmcs_conf, &vmx_cap) < 0)
> - *(int *)rtn = -EIO;
> + return -EIO;
> if (nested)
> nested_vmx_setup_ctls_msrs(&vmcs_conf.nested, vmx_cap.ept,
> enable_apicv);
> if (memcmp(&vmcs_config, &vmcs_conf, sizeof(struct vmcs_config)) != 0) {
> printk(KERN_ERR "kvm: CPU %d feature inconsistency!\n",
> smp_processor_id());
> - *(int *)rtn = -EIO;
> + return -EIO;
> }
> + return 0;
> }
>
> static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c09507057743..6214c27b0c2a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9042,9 +9042,9 @@ void kvm_arch_hardware_unsetup(void)
> kvm_x86_ops->hardware_unsetup();
> }
>
> -void kvm_arch_check_processor_compat(void *rtn)
> +int kvm_arch_check_processor_compat(void)
> {
> - kvm_x86_ops->check_processor_compatibility(rtn);
> + return kvm_x86_ops->check_processor_compatibility();
> }
>
> bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu)
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 640a03642766..0ddef348b9b0 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -842,7 +842,7 @@ int kvm_arch_hardware_enable(void);
> void kvm_arch_hardware_disable(void);
> int kvm_arch_hardware_setup(void);
> void kvm_arch_hardware_unsetup(void);
> -void kvm_arch_check_processor_compat(void *rtn);
> +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/arm/arm.c b/virt/kvm/arm/arm.c
> index be4ec5f3ba5f..67ecadbd8961 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -105,9 +105,9 @@ int kvm_arch_hardware_setup(void)
> return 0;
> }
>
> -void kvm_arch_check_processor_compat(void *rtn)
> +int kvm_arch_check_processor_compat(void)
> {
> - *(int *)rtn = 0;
> + return 0;
> }
>
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 4bb20f2b2a69..41effae3f9ec 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4135,6 +4135,11 @@ static void kvm_sched_out(struct preempt_notifier *pn,
> kvm_arch_vcpu_put(vcpu);
> }
>
> +static void check_processor_compat(void *rtn)
> +{
> + *(int *)rtn = kvm_arch_check_processor_compat();
> +}
> +
> int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
> struct module *module)
> {
> @@ -4166,9 +4171,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
> goto out_free_0a;
>
> for_each_online_cpu(cpu) {
> - smp_call_function_single(cpu,
> - kvm_arch_check_processor_compat,
> - &r, 1);
> + smp_call_function_single(cpu, check_processor_compat, &r, 1);
> if (r < 0)
> goto out_free_1;
> }
>

Queued for 5.3, thanks.

Paolo