linux-kernel - [PATCH v7 07/26] x86/fpu/xstate: Warn if kernel dynamic xfeatures detected in normal fpstate

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Message-Id: <20231124055330.138870-8-weijiang.yang@intel.com>
Date:   Fri, 24 Nov 2023 00:53:11 -0500
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     seanjc@...gle.com, pbonzini@...hat.com, dave.hansen@...el.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, chao.gao@...el.com,
        rick.p.edgecombe@...el.com, mlevitsk@...hat.com,
        john.allen@....com, weijiang.yang@...el.com
Subject: [PATCH v7 07/26] x86/fpu/xstate: Warn if kernel dynamic xfeatures detected in normal fpstate

Kernel dynamic xfeatures now are __ONLY__ enabled for guest fpstate, i.e.,
none for normal kernel fpstate. The bits are added when guest FPU config
is initialized. Guest fpstate is allocated with fpstate->is_guest set to
%true.

For normal fpstate, the bits should have been removed when initializes
kernel FPU config settings, WARN_ONCE() if kernel detects normal fpstate
xfeatures contains kernel dynamic xfeatures before executes xsaves.

Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kernel/fpu/xstate.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
index c032acb56306..d45f3e570e69 100644
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -186,6 +186,9 @@ static inline void os_xsave(struct fpstate *fpstate)
 	WARN_ON_FPU(!alternatives_patched);
 	xfd_validate_state(fpstate, mask, false);
 
+	WARN_ON_FPU(!fpstate->is_guest &&
+		    (mask & XFEATURE_MASK_KERNEL_DYNAMIC));
+
 	XSTATE_XSAVE(&fpstate->regs.xsave, lmask, hmask, err);
 
 	/* We should never fault when copying to a kernel buffer: */
-- 
2.27.0