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Date: Mon, 12 Feb 2024 21:56:40 +0200
Message-Id: <CZ3D5SNJ8O14.2AQBOPEH3DFSG@kernel.org>
From: "Jarkko Sakkinen" <jarkko@kernel.org>
To: "Haitao Huang" <haitao.huang@linux.intel.com>,
 <dave.hansen@linux.intel.com>, <tj@kernel.org>, <mkoutny@suse.com>,
 <linux-kernel@vger.kernel.org>, <linux-sgx@vger.kernel.org>,
 <x86@kernel.org>, <cgroups@vger.kernel.org>, <tglx@linutronix.de>,
 <mingo@redhat.com>, <bp@alien8.de>, <hpa@zytor.com>,
 <sohil.mehta@intel.com>, <tim.c.chen@linux.intel.com>
Cc: <zhiquan1.li@intel.com>, <kristen@linux.intel.com>, <seanjc@google.com>,
 <zhanb@microsoft.com>, <anakrish@microsoft.com>,
 <mikko.ylinen@linux.intel.com>, <yangjie@microsoft.com>,
 <chrisyan@microsoft.com>
Subject: Re: [PATCH v9 11/15] x86/sgx: Abstract check for global reclaimable
 pages
References: <20240205210638.157741-1-haitao.huang@linux.intel.com>
 <20240205210638.157741-12-haitao.huang@linux.intel.com>
In-Reply-To: <20240205210638.157741-12-haitao.huang@linux.intel.com>

On Mon Feb 5, 2024 at 11:06 PM EET, Haitao Huang wrote:
> From: Kristen Carlson Accardi <kristen@linux.intel.com>
>
> To determine if any page available for reclamation at the global level,
> only checking for emptiness of the global LRU is not adequate when pages
> are tracked in multiple LRUs, one per cgroup. For this purpose, create a
> new helper, sgx_can_reclaim(), currently only checks the global LRU,
> later will check emptiness of LRUs of all cgroups when per-cgroup
> tracking is turned on. Replace all the checks of the global LRU,
> list_empty(&sgx_global_lru.reclaimable), with calls to
> sgx_can_reclaim().
>
> Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> Co-developed-by: Haitao Huang <haitao.huang@linux.intel.com>
> Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
> ---
> v7:
> - Split this out from the big patch, #10 in V6. (Dave, Kai)
> ---
>  arch/x86/kernel/cpu/sgx/main.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/mai=
n.c
> index 2279ae967707..6b0c26cac621 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -37,6 +37,11 @@ static inline struct sgx_epc_lru_list *sgx_lru_list(st=
ruct sgx_epc_page *epc_pag
>  	return &sgx_global_lru;
>  }
> =20

/*
 * Description
 */
> +static inline bool sgx_can_reclaim(void)
> +{
> +	return !list_empty(&sgx_global_lru.reclaimable);
> +}
> +
>  static atomic_long_t sgx_nr_free_pages =3D ATOMIC_LONG_INIT(0);
> =20
>  /* Nodes with one or more EPC sections. */
> @@ -398,7 +403,7 @@ unsigned int sgx_reclaim_pages(struct sgx_epc_lru_lis=
t *lru, unsigned int *nr_to
>  static bool sgx_should_reclaim(unsigned long watermark)
>  {
>  	return atomic_long_read(&sgx_nr_free_pages) < watermark &&
> -	       !list_empty(&sgx_global_lru.reclaimable);
> +		sgx_can_reclaim();
>  }
> =20
>  static void sgx_reclaim_pages_global(bool indirect)
> @@ -601,7 +606,7 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, =
bool reclaim)
>  			break;
>  		}
> =20
> -		if (list_empty(&sgx_global_lru.reclaimable)) {
> +		if (!sgx_can_reclaim()) {
>  			page =3D ERR_PTR(-ENOMEM);
>  			break;
>  		}

BR, Jarkko