linux-kernel - Re: [PATCH v2 08/11] KVM: x86: Pass reference pvclock as a param to kvm_setup_guest

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Message-ID: <792ae6f4-903f-41b2-a0f2-369d92a1fc3f@xen.org>
Date: Tue, 4 Feb 2025 09:33:59 +0000
From: Paul Durrant <xadimgnik@...il.com>
To: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>, David Woodhouse <dwmw2@...radead.org>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzbot+352e553a86e0d75f5120@...kaller.appspotmail.com,
 Paul Durrant <pdurrant@...zon.com>, David Woodhouse <dwmw@...zon.co.uk>,
 Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH v2 08/11] KVM: x86: Pass reference pvclock as a param to
 kvm_setup_guest_pvclock()

On 01/02/2025 01:38, Sean Christopherson wrote:
> Pass the reference pvclock structure that's used to setup each individual
> pvclock as a parameter to kvm_setup_guest_pvclock() as a preparatory step
> toward removing kvm_vcpu_arch.hv_clock.
> 
> No functional change intended.
> 
> Reviewed-by: Paul Durrant <paul@....org>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   arch/x86/kvm/x86.c | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 5f3ad13a8ac7..06d27b3cc207 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3116,17 +3116,17 @@ u64 get_kvmclock_ns(struct kvm *kvm)
>   	return data.clock;
>   }
>   
> -static void kvm_setup_guest_pvclock(struct kvm_vcpu *v,
> +static void kvm_setup_guest_pvclock(struct pvclock_vcpu_time_info *ref_hv_clock,
> +				    struct kvm_vcpu *vcpu,

So, here 'v' becomes 'vcpu'

>   				    struct gfn_to_pfn_cache *gpc,
>   				    unsigned int offset,
>   				    bool force_tsc_unstable)
>   {
> -	struct kvm_vcpu_arch *vcpu = &v->arch;
>   	struct pvclock_vcpu_time_info *guest_hv_clock;
>   	struct pvclock_vcpu_time_info hv_clock;
>   	unsigned long flags;
>   
> -	memcpy(&hv_clock, &vcpu->hv_clock, sizeof(hv_clock));
> +	memcpy(&hv_clock, ref_hv_clock, sizeof(hv_clock));
>   
>   	read_lock_irqsave(&gpc->lock, flags);
>   	while (!kvm_gpc_check(gpc, offset + sizeof(*guest_hv_clock))) {
> @@ -3165,7 +3165,7 @@ static void kvm_setup_guest_pvclock(struct kvm_vcpu *v,
>   	kvm_gpc_mark_dirty_in_slot(gpc);
>   	read_unlock_irqrestore(&gpc->lock, flags);
>   
> -	trace_kvm_pvclock_update(v->vcpu_id, &hv_clock);
> +	trace_kvm_pvclock_update(vcpu->vcpu_id, &hv_clock);
>   }
>   
>   static int kvm_guest_time_update(struct kvm_vcpu *v)
> @@ -3272,18 +3272,18 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
>   			vcpu->hv_clock.flags |= PVCLOCK_GUEST_STOPPED;
>   			vcpu->pvclock_set_guest_stopped_request = false;
>   		}
> -		kvm_setup_guest_pvclock(v, &vcpu->pv_time, 0, false);
> +		kvm_setup_guest_pvclock(&vcpu->hv_clock, v, &vcpu->pv_time, 0, false);

Yet here an below you still use 'v'. Does this actually compile?

>   
>   		vcpu->hv_clock.flags &= ~PVCLOCK_GUEST_STOPPED;
>   	}
>   
>   #ifdef CONFIG_KVM_XEN
>   	if (vcpu->xen.vcpu_info_cache.active)
> -		kvm_setup_guest_pvclock(v, &vcpu->xen.vcpu_info_cache,
> +		kvm_setup_guest_pvclock(&vcpu->hv_clock, v, &vcpu->xen.vcpu_info_cache,
>   					offsetof(struct compat_vcpu_info, time),
>   					xen_pvclock_tsc_unstable);
>   	if (vcpu->xen.vcpu_time_info_cache.active)
> -		kvm_setup_guest_pvclock(v, &vcpu->xen.vcpu_time_info_cache, 0,
> +		kvm_setup_guest_pvclock(&vcpu->hv_clock, v, &vcpu->xen.vcpu_time_info_cache, 0,
>   					xen_pvclock_tsc_unstable);
>   #endif
>   	kvm_hv_setup_tsc_page(v->kvm, &vcpu->hv_clock);