Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Message-ID: <6e51fdacc2c1d834258f00ad8cc268b8d782eca7.camel@kernel.org>
Subject: Re: [PATCH] x86/sgx: Fix free page accounting
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Reinette Chatre <reinette.chatre@intel.com>,
        dave.hansen@linux.intel.com, tglx@linutronix.de, bp@alien8.de,
        mingo@redhat.com, linux-sgx@vger.kernel.org, x86@kernel.org
Cc:     seanjc@google.com, tony.luck@intel.com, hpa@zytor.com,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Date:   Sun, 07 Nov 2021 18:45:35 +0200
In-Reply-To: <373992d869cd356ce9e9afe43ef4934b70d604fd.1636049678.git.reinette.chatre@intel.com>
References: <373992d869cd356ce9e9afe43ef4934b70d604fd.1636049678.git.reinette.chatre@intel.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.40.4-1 
MIME-Version: 1.0
Precedence: bulk

On Thu, 2021-11-04 at 11:28 -0700, Reinette Chatre wrote:
> The consequence of sgx_nr_free_pages not being protected is that
> its value may not accurately reflect the actual number of free
> pages on the system, impacting the availability of free pages in
> support of many flows. The problematic scenario is when the
> reclaimer never runs because it believes there to be sufficient
> free pages while any attempt to allocate a page fails because there
> are no free pages available. The worst scenario observed was a
> user space hang because of repeated page faults caused by
> no free pages ever made available.

Can you go in detail with the "concrete scenario" in the commit
message? It does not have to describe all the possible scenarios
but at least one sequence of events.

/Jarkko