From: Thomas Gleixner <tglx@linutronix.de>
To: Adamos Ttofari <attofari@amazon.de>, chang.seok.bae@intel.com
Cc: attofari@amazon.de, abusse@amazon.de,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Kyle Huey <me@kylehuey.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] x86: fpu: Keep xfd_state always in sync with MSR_IA32_XFD
Date: Fri, 19 May 2023 17:03:23 +0200 [thread overview]
Message-ID: <87ilco4b44.ffs@tglx> (raw)
In-Reply-To: <20230519112315.30616-1-attofari@amazon.de>
On Fri, May 19 2023 at 11:23, Adamos Ttofari wrote:
> Commit 672365477ae8 ("x86/fpu: Update XFD state where required") and
> commit 8bf26758ca96 ("x86/fpu: Add XFD state to fpstate") introduced a
> per CPU variable xfd_state to keep the MSR_IA32_XFD value cached. In
> order to avoid unnecessary writes to the MSR.
>
> On CPU hotplug MSR_IA32_XFD is reset to the init_fpstate.xfd, which
> wipes out any stale state. But the per CPU cached xfd value is not
> reset, which brings them out of sync.
>
> As a consequence a subsequent xfd_update_state() might fail to update
> the MSR which in turn can result in XRSTOR raising a #NM in kernel
> space, which crashes the kernel.
>
> To address the issue mentioned, initialize xfd_state together with
> MSR_IA32_XFD.
>
> Fixes: 672365477ae8 ("x86/fpu: Update XFD state where required")
>
> Signed-off-by: Adamos Ttofari <attofari@amazon.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
next prev parent reply other threads:[~2023-05-19 15:03 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-11 15:28 [PATCH] fpu: xstate: Keep xfd_state always in-sync with IA32_XFD MSR Adamos Ttofari
2023-05-11 17:59 ` Dave Hansen
2023-05-11 19:11 ` Thomas Gleixner
2023-05-12 17:46 ` Chang S. Bae
2023-05-12 11:38 ` [PATCH v2] x86: fpu: Keep xfd_state always in sync with MSR_IA32_XFD Adamos Ttofari
2023-05-12 12:52 ` Thomas Gleixner
2023-05-19 11:23 ` [PATCH v3] " Adamos Ttofari
2023-05-19 15:03 ` Thomas Gleixner [this message]
2023-05-19 22:21 ` Chang S. Bae
2023-06-03 15:24 ` [PATCH] selftests/x86/amx: Add a CPU hotplug test Chang S. Bae
2024-03-22 23:04 ` [PATCH v4] x86/fpu: Keep xfd_state always in sync with MSR_IA32_XFD Chang S. Bae
2024-03-24 3:15 ` [tip: x86/urgent] x86/fpu: Keep xfd_state " tip-bot2 for Adamos Ttofari
2023-05-16 21:35 ` [PATCH v2] x86: fpu: Keep xfd_state always " Chang S. Bae
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