From: Randy Dunlap <rdunlap@infradead.org>
To: Balbir Singh <sblbir@amazon.com>,
tglx@linutronix.de, linux-kernel@vger.kernel.org
Cc: jpoimboe@redhat.com, tony.luck@intel.com, keescook@chromium.org,
benh@kernel.crashing.org, x86@kernel.org, dave.hansen@intel.com
Subject: Re: [PATCH v2 4/4] arch/x86: Add L1D flushing Documentation
Date: Tue, 19 May 2020 08:39:49 -0700 [thread overview]
Message-ID: <5def424d-c7d5-c6fa-60b9-363f6bca6bc6@infradead.org> (raw)
In-Reply-To: <20200406031946.11815-5-sblbir@amazon.com>
Hi--
Comments below. Sorry about the delay.
On 4/5/20 8:19 PM, Balbir Singh wrote:
> Add documentation of l1d flushing, explain the need for the
> feature and how it can be used.
>
> Signed-off-by: Balbir Singh <sblbir@amazon.com>
> ---
> Documentation/admin-guide/hw-vuln/index.rst | 1 +
> .../admin-guide/hw-vuln/l1d_flush.rst | 40 +++++++++++++++++++
> 2 files changed, 41 insertions(+)
> create mode 100644 Documentation/admin-guide/hw-vuln/l1d_flush.rst
> diff --git a/Documentation/admin-guide/hw-vuln/l1d_flush.rst b/Documentation/admin-guide/hw-vuln/l1d_flush.rst
> new file mode 100644
> index 000000000000..73ee9e491a74
> --- /dev/null
> +++ b/Documentation/admin-guide/hw-vuln/l1d_flush.rst
> @@ -0,0 +1,40 @@
> +L1D Flushing for the paranoid
> +=============================
> +
> +With an increasing number of vulnerabilities being reported around data
> +leaks from L1D, a new user space mechanism to flush the L1D cache on
> +context switch is added to the kernel. This should help address
> +CVE-2020-0550 and for paranoid applications, keep them safe from any
> +yet to be discovered vulnerabilities, related to leaks from the L1D
> +cache.
> +
> +Tasks can opt in to this mechanism by using an architecture specific
> +prctl (x86 only at the moment).
> +
> +Related CVES
CVEs
> +------------
> +At the present moment, the following CVEs can be addressed by this
> +mechanism
> +
> + ============= ======================== ==================
> + CVE-2020-0550 Improper Data Forwarding OS related aspects
> + ============= ======================== ==================
> +
> +Usage Guidelines
> +----------------
> +Applications can call ``arch_prctl(2)`` with one of these two arguments
end above sentence with period or colon (colon might require the following
bullet items to be indented -- I'm not sure about that).
> +
> +1. ARCH_SET_L1D_FLUSH - flush the L1D cache on context switch (out)
> +2. ARCH_GET_L1D_FLUSH - get the current state of the L1D cache flush, returns 1
> + if set and 0 if not set.
> +
> +**NOTE**: The feature is disabled by default, applications to need to specifically
default; applications need to
> +opt into the feature to enable it.
> +
> +Mitigation
> +----------
> +When ARCH_SET_L1D_FLUSH is enabled for a task, on switching tasks (when
> +the address space changes), a flush of the L1D cache is performed for
> +the task when it leaves the CPU. If the underlying CPU supports L1D
> +flushing in hardware, the hardware mechanism is used, otherwise a software
> +fallback, similar to the mechanism used by L1TF is used.
>
thanks.
--
~Randy
next prev parent reply other threads:[~2020-05-19 15:39 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-06 3:19 [PATCH v2 0/4] arch/x86: Optionally flush L1D on context switch Balbir Singh
2020-04-06 3:19 ` [PATCH v2 1/4] arch/x86/kvm: Refactor l1d flush lifecycle management Balbir Singh
2020-04-07 18:21 ` Kees Cook
2020-04-06 3:19 ` [PATCH v2 2/4] arch/x86: Refactor tlbflush and l1d flush Balbir Singh
2020-04-07 18:25 ` Kees Cook
2020-04-08 0:22 ` Singh, Balbir
2020-04-06 3:19 ` [PATCH v2 3/4] arch/x86: Optionally flush L1D on context switch Balbir Singh
2020-04-07 18:26 ` Kees Cook
2020-04-07 23:37 ` Benjamin Herrenschmidt
2020-04-07 23:39 ` Singh, Balbir
2020-04-07 23:49 ` Thomas Gleixner
2020-05-19 23:41 ` Singh, Balbir
2020-04-07 23:52 ` Thomas Gleixner
2020-04-08 0:14 ` Singh, Balbir
2020-04-06 3:19 ` [PATCH v2 4/4] arch/x86: Add L1D flushing Documentation Balbir Singh
2020-05-19 15:39 ` Randy Dunlap [this message]
2020-05-20 0:47 ` Singh, Balbir
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5def424d-c7d5-c6fa-60b9-363f6bca6bc6@infradead.org \
--to=rdunlap@infradead.org \
--cc=benh@kernel.crashing.org \
--cc=dave.hansen@intel.com \
--cc=jpoimboe@redhat.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=sblbir@amazon.com \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).