From: Dave Hansen <dave.hansen@intel.com>
To: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Cc: Rudi Horn <rudi.horn@oracle.com>,
Thomas Gleixner <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Joe Jin <joe.jin@oracle.com>, Jeff Xu <jeffxu@chromium.org>
Subject: Re: [RFC] Restore PKRU to user-defined value after signal handling
Date: Thu, 7 Nov 2024 16:26:15 -0800 [thread overview]
Message-ID: <59464733-17d1-4b43-83f4-e85a8389638d@intel.com> (raw)
In-Reply-To: <4111AC83-7A7C-4268-B294-3AB75C0EC451@oracle.com>
On 11/7/24 15:56, Aruna Ramakrishna wrote:
> If it is calcuated by the kernel, is there a chance that we could inadvertently
> set XINUSE[i] to 1 for more components other than just PKRU? Since it is
> possible that some other component was set to its init state by XSAVE,
XINUSE is exposed in the ISA via XGETBV(1). If it were _totally_ racy
and the CPU could change it willy nilly at any time, it couldn't be
sanely exposed.
I think it's safe to assume that if you use XGETBV(1) that the state is
sticky at least until there's an explicit change to a state component.
If you're really worried about this, we could go ask the hardware folks.
next prev parent reply other threads:[~2024-11-08 0:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-06 18:33 Aruna Ramakrishna
2024-11-06 19:27 ` Dave Hansen
2024-11-06 19:40 ` Aruna Ramakrishna
2024-11-06 19:47 ` Dave Hansen
2024-11-07 11:41 ` Rudi Horn
2024-11-07 15:56 ` Dave Hansen
2024-11-07 16:03 ` Dave Hansen
2024-11-07 23:56 ` Aruna Ramakrishna
2024-11-08 0:26 ` Dave Hansen [this message]
2024-11-08 9:58 ` Rudi Horn
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