On Wed, Nov 02, 2022 at 11:18:35PM +0000, Sean Christopherson wrote:
> Now that kvm_arch_hardware_setup() is called immediately after
> kvm_arch_init(), fold the guts of kvm_arch_hardware_(un)setup() into
> kvm_arch_{init,exit}() as a step towards dropping one of the hooks.
>
> To avoid having to unwind various setup, e.g registration of several
> notifiers, slot in the vendor hardware setup before the registration of
> said notifiers and callbacks. Introducing a functional change while
> moving code is less than ideal, but the alternative is adding a pile of
> unwinding code, which is much more error prone, e.g. several attempts to
> move the setup code verbatim all introduced bugs.
>
> Add a comment to document that kvm_ops_update() is effectively the point
> of no return, e.g. it sets the kvm_x86_ops.hardware_enable canary and so
> needs to be unwound.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 121 +++++++++++++++++++++++----------------------
> 1 file changed, 63 insertions(+), 58 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9a7702b1c563..80ee580a9cd4 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9252,6 +9252,24 @@ static struct notifier_block pvclock_gtod_notifier = {
> };
> #endif
>
> +static inline void kvm_ops_update(struct kvm_x86_init_ops *ops)
> +{
> + memcpy(&kvm_x86_ops, ops->runtime_ops, sizeof(kvm_x86_ops));
> +
> +#define __KVM_X86_OP(func) \
> + static_call_update(kvm_x86_##func, kvm_x86_ops.func);
> +#define KVM_X86_OP(func) \
> + WARN_ON(!kvm_x86_ops.func); __KVM_X86_OP(func)
> +#define KVM_X86_OP_OPTIONAL __KVM_X86_OP
> +#define KVM_X86_OP_OPTIONAL_RET0(func) \
> + static_call_update(kvm_x86_##func, (void *)kvm_x86_ops.func ? : \
> + (void *)__static_call_return0);
> +#include <asm/kvm-x86-ops.h>
> +#undef __KVM_X86_OP
> +
> + kvm_pmu_ops_update(ops->pmu_ops);
> +}
> +
> int kvm_arch_init(void *opaque)
> {
> struct kvm_x86_init_ops *ops = opaque;
> @@ -9325,6 +9343,24 @@ int kvm_arch_init(void *opaque)
> kvm_caps.supported_xcr0 = host_xcr0 & KVM_SUPPORTED_XCR0;
> }
>
> + rdmsrl_safe(MSR_EFER, &host_efer);
> +
> + if (boot_cpu_has(X86_FEATURE_XSAVES))
> + rdmsrl(MSR_IA32_XSS, host_xss);
> +
> + kvm_init_pmu_capability();
> +
> + r = ops->hardware_setup();
> + if (r != 0)
> + goto out_mmu_exit;
The failure case of ops->hardware_setup() is unwound
by kvm_arch_exit() before this patch, do we need to
keep that old behavior ?
> +
> + /*
> + * Point of no return! DO NOT add error paths below this point unless
> + * absolutely necessary, as most operations from this point forward
> + * require unwinding.
> + */
> + kvm_ops_update(ops);
> +
> kvm_timer_init();
>
> if (pi_inject_timer == -1)
> @@ -9336,8 +9372,32 @@ int kvm_arch_init(void *opaque)
> set_hv_tscchange_cb(kvm_hyperv_tsc_notifier);
> #endif
>
> + kvm_register_perf_callbacks(ops->handle_intel_pt_intr);
> +
> + if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
> + kvm_caps.supported_xss = 0;
> +
> +#define __kvm_cpu_cap_has(UNUSED_, f) kvm_cpu_cap_has(f)
> + cr4_reserved_bits = __cr4_reserved_bits(__kvm_cpu_cap_has, UNUSED_);
> +#undef __kvm_cpu_cap_has
> +
> + if (kvm_caps.has_tsc_control) {
> + /*
> + * Make sure the user can only configure tsc_khz values that
> + * fit into a signed integer.
> + * A min value is not calculated because it will always
> + * be 1 on all machines.
> + */
> + u64 max = min(0x7fffffffULL,
> + __scale_tsc(kvm_caps.max_tsc_scaling_ratio, tsc_khz));
> + kvm_caps.max_guest_tsc_khz = max;
> + }
> + kvm_caps.default_tsc_scaling_ratio = 1ULL << kvm_caps.tsc_scaling_ratio_frac_bits;
> + kvm_init_msr_list();
> return 0;
>
> +out_mmu_exit:
> + kvm_mmu_vendor_module_exit();
> out_free_percpu:
> free_percpu(user_return_msrs);
> out_free_x86_emulator_cache:
> @@ -9347,6 +9407,8 @@ int kvm_arch_init(void *opaque)
>
> void kvm_arch_exit(void)
> {
> + kvm_unregister_perf_callbacks();
> +
> #ifdef CONFIG_X86_64
> if (hypervisor_is_type(X86_HYPER_MS_HYPERV))
> clear_hv_tscchange_cb();
> @@ -9362,6 +9424,7 @@ void kvm_arch_exit(void)
> irq_work_sync(&pvclock_irq_work);
> cancel_work_sync(&pvclock_gtod_work);
> #endif
> + static_call(kvm_x86_hardware_unsetup)();
> kvm_x86_ops.hardware_enable = NULL;
> kvm_mmu_vendor_module_exit();
> free_percpu(user_return_msrs);
> @@ -11922,72 +11985,14 @@ void kvm_arch_hardware_disable(void)
> drop_user_return_notifiers();
> }
>
> -static inline void kvm_ops_update(struct kvm_x86_init_ops *ops)
> -{
> - memcpy(&kvm_x86_ops, ops->runtime_ops, sizeof(kvm_x86_ops));
> -
> -#define __KVM_X86_OP(func) \
> - static_call_update(kvm_x86_##func, kvm_x86_ops.func);
> -#define KVM_X86_OP(func) \
> - WARN_ON(!kvm_x86_ops.func); __KVM_X86_OP(func)
> -#define KVM_X86_OP_OPTIONAL __KVM_X86_OP
> -#define KVM_X86_OP_OPTIONAL_RET0(func) \
> - static_call_update(kvm_x86_##func, (void *)kvm_x86_ops.func ? : \
> - (void *)__static_call_return0);
> -#include <asm/kvm-x86-ops.h>
> -#undef __KVM_X86_OP
> -
> - kvm_pmu_ops_update(ops->pmu_ops);
> -}
> -
> int kvm_arch_hardware_setup(void *opaque)
> {
> - struct kvm_x86_init_ops *ops = opaque;
> - int r;
> -
> - rdmsrl_safe(MSR_EFER, &host_efer);
> -
> - if (boot_cpu_has(X86_FEATURE_XSAVES))
> - rdmsrl(MSR_IA32_XSS, host_xss);
> -
> - kvm_init_pmu_capability();
> -
> - r = ops->hardware_setup();
> - if (r != 0)
> - return r;
> -
> - kvm_ops_update(ops);
> -
> - kvm_register_perf_callbacks(ops->handle_intel_pt_intr);
> -
> - if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
> - kvm_caps.supported_xss = 0;
> -
> -#define __kvm_cpu_cap_has(UNUSED_, f) kvm_cpu_cap_has(f)
> - cr4_reserved_bits = __cr4_reserved_bits(__kvm_cpu_cap_has, UNUSED_);
> -#undef __kvm_cpu_cap_has
> -
> - if (kvm_caps.has_tsc_control) {
> - /*
> - * Make sure the user can only configure tsc_khz values that
> - * fit into a signed integer.
> - * A min value is not calculated because it will always
> - * be 1 on all machines.
> - */
> - u64 max = min(0x7fffffffULL,
> - __scale_tsc(kvm_caps.max_tsc_scaling_ratio, tsc_khz));
> - kvm_caps.max_guest_tsc_khz = max;
> - }
> - kvm_caps.default_tsc_scaling_ratio = 1ULL << kvm_caps.tsc_scaling_ratio_frac_bits;
> - kvm_init_msr_list();
> return 0;
> }
>
> void kvm_arch_hardware_unsetup(void)
> {
> - kvm_unregister_perf_callbacks();
>
> - static_call(kvm_x86_hardware_unsetup)();
> }
>
> int kvm_arch_check_processor_compat(void *opaque)
> --
> 2.38.1.431.g37b22c650d-goog
>
