linux-kernel - [patch 6/7] x86/fpu/xstate: Handle supervisor states in XSTATE permissions

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Message-ID: <20220324134623.681768598@linutronix.de>
Date:   Thu, 24 Mar 2022 14:47:14 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Chang S. Bae" <chang.seok.bae@...el.com>,
        Paolo Bonzini <bonzini@....org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>
Subject: [patch 6/7] x86/fpu/xstate: Handle supervisor states in XSTATE permissions

The size calculation in __xstate_request_perm() fails to take supervisor
states into account because the permission bitmap is only relevant for user
states.

Up to 5.17 this does not matter because there are no supervisor states
supported, but the (re)enabling of ENQCMD makes them available.

Fixes: 7c1ef59145f1 ("x86/cpufeatures: Re-enable ENQCMD")
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Paolo Bonzini <bonzini@....org>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Tony Luck <tony.luck@...el.com>
---
 arch/x86/kernel/fpu/xstate.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1566,6 +1566,9 @@ static int __xstate_request_perm(u64 per
 
 	/* Calculate the resulting kernel state size */
 	mask = permitted | requested;
+	/* Take supervisor states into account on the host */
+	if (!guest)
+		mask |= xfeatures_mask_supervisor();
 	ksize = xstate_calculate_size(mask, compacted);
 
 	/* Calculate the resulting user state size */