linux-kernel - Re: [PATCH] drm/i915/gvt: Convert from atomic_t to refcount_t on intel_vgpu_ppgtt_spt->refcount

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Message-ID: <20210721020009.GG13928@zhen-hp.sh.intel.com>
Date:   Wed, 21 Jul 2021 10:00:09 +0800
From:   Zhenyu Wang <zhenyuw@...ux.intel.com>
To:     Xiyu Yang <xiyuyang19@...an.edu.cn>
Cc:     Zhi Wang <zhi.a.wang@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Xin Tan <tanxin.ctf@...il.com>,
        yuanxzhang@...an.edu.cn
Subject: Re: [PATCH] drm/i915/gvt: Convert from atomic_t to refcount_t on
 intel_vgpu_ppgtt_spt->refcount

On 2021.07.16 18:41:38 +0800, Xiyu Yang wrote:
> refcount_t type and corresponding API can protect refcounters from
> accidental underflow and overflow and further use-after-free situations
>

Thanks for the patch. Is there any specific problem you run with current code?
Any shadow ppgtt error?

> Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
> ---
>  drivers/gpu/drm/i915/gvt/gtt.c | 11 ++++++-----
>  drivers/gpu/drm/i915/gvt/gtt.h |  3 ++-
>  2 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
> index cc2c05e18206..62f3daff5a36 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> @@ -841,7 +841,7 @@ static struct intel_vgpu_ppgtt_spt *ppgtt_alloc_spt(
>  	}
>  
>  	spt->vgpu = vgpu;
> -	atomic_set(&spt->refcount, 1);
> +	refcount_set(&spt->refcount, 1);
>  	INIT_LIST_HEAD(&spt->post_shadow_list);
>  
>  	/*
> @@ -927,18 +927,19 @@ static struct intel_vgpu_ppgtt_spt *ppgtt_alloc_spt_gfn(
>  
>  static inline void ppgtt_get_spt(struct intel_vgpu_ppgtt_spt *spt)
>  {
> -	int v = atomic_read(&spt->refcount);
> +	int v = refcount_read(&spt->refcount);
>  
>  	trace_spt_refcount(spt->vgpu->id, "inc", spt, v, (v + 1));
> -	atomic_inc(&spt->refcount);
> +	refcount_inc(&spt->refcount);
>  }
>  
>  static inline int ppgtt_put_spt(struct intel_vgpu_ppgtt_spt *spt)
>  {
> -	int v = atomic_read(&spt->refcount);
> +	int v = refcount_read(&spt->refcount);
>  
>  	trace_spt_refcount(spt->vgpu->id, "dec", spt, v, (v - 1));
> -	return atomic_dec_return(&spt->refcount);
> +	refcount_dec(&spt->refcount);
> +	return refcount_read(&spt->refcount);
>  }
>  
>  static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt);
> diff --git a/drivers/gpu/drm/i915/gvt/gtt.h b/drivers/gpu/drm/i915/gvt/gtt.h
> index 3bf45672ef98..944c2d0739df 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.h
> +++ b/drivers/gpu/drm/i915/gvt/gtt.h
> @@ -38,6 +38,7 @@
>  #include <linux/kref.h>
>  #include <linux/mutex.h>
>  #include <linux/radix-tree.h>
> +#include <linux/refcount.h>
>  
>  #include "gt/intel_gtt.h"
>  
> @@ -243,7 +244,7 @@ struct intel_vgpu_oos_page {
>  
>  /* Represent a vgpu shadow page table. */
>  struct intel_vgpu_ppgtt_spt {
> -	atomic_t refcount;
> +	refcount_t refcount;
>  	struct intel_vgpu *vgpu;
>  
>  	struct {
> -- 
> 2.7.4
> 
> _______________________________________________
> intel-gvt-dev mailing list
> intel-gvt-dev@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

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