linux-kernel - Re: [PATCH v2 15/27] drm/i915/gvt: Don't bother removing write-protection on to-be-deleted slot

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Message-ID: <ZBQXMmjKNPIyowUF@yzhao56-desk.sh.intel.com>
Date:   Fri, 17 Mar 2023 15:30:58 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>, <kvm@...r.kernel.org>,
        <intel-gvt-dev@...ts.freedesktop.org>,
        <intel-gfx@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH v2 15/27] drm/i915/gvt: Don't bother removing
 write-protection on to-be-deleted slot

Reviewed-by: Yan Zhao <yan.y.zhao@...el.com>

On Fri, Mar 10, 2023 at 04:22:46PM -0800, Sean Christopherson wrote:
> When handling a slot "flush", don't call back into KVM to drop write
> protection for gfns in the slot.  Now that KVM rejects attempts to move
> memory slots while KVMGT is attached, the only time a slot is "flushed"
> is when it's being removed, i.e. the memslot and all its write-tracking
> metadata is about to be deleted.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  drivers/gpu/drm/i915/gvt/kvmgt.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 292750dc819f..577712ea4893 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -1644,14 +1644,8 @@ static void kvmgt_page_track_flush_slot(struct kvm *kvm,
>  
>  	for (i = 0; i < slot->npages; i++) {
>  		gfn = slot->base_gfn + i;
> -		if (kvmgt_gfn_is_write_protected(info, gfn)) {
> -			write_lock(&kvm->mmu_lock);
> -			kvm_slot_page_track_remove_page(kvm, slot, gfn,
> -						KVM_PAGE_TRACK_WRITE);
> -			write_unlock(&kvm->mmu_lock);
> -
> +		if (kvmgt_gfn_is_write_protected(info, gfn))
>  			kvmgt_protect_table_del(info, gfn);
> -		}
>  	}
>  	mutex_unlock(&info->vgpu_lock);
>  }
> -- 
> 2.40.0.rc1.284.g88254d51c5-goog
>