From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F37DA1862D for ; Wed, 15 Nov 2023 12:24:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Fl7yn3wJ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=fhDP8pl7DmtQJLtjZ7NvRUrsrSgQFICjei3CoSbh6X4=; b=Fl7yn3wJedcCW077qb0CEnptMW 15Iro+TMi2+101PsQ6KRgqyJ91TvxOKYbE7hpqFOSj6mbd2tJkFM//Dqx1pnEB4hmVOP6w/askEZ2 dwgaH5NSzYOv39+uTod+A9GPAWKrxwFuILTlQWEaxyndyG3UwgmYyJ8DO5ftw0oQQAPsxiwdTz5gY MFa2PG2TouZAEStOBo5Q08RnpasMyt+xnDH/HQyF7PACYRvj0/QxlE5hivGMfkZ5mg7USwriXJntz U6qyn68g2/7njPfjG4H5Y+A9o1pdTpC2Qb2lSg1pZBIMNmi4rq+Vbp1GF44X47N7sqSTp7cvUzYnU NEY7peRg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1r3Evn-00E7nE-Mo; Wed, 15 Nov 2023 12:23:43 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 5CB21300427; Wed, 15 Nov 2023 13:23:43 +0100 (CET) Date: Wed, 15 Nov 2023 13:23:43 +0100 From: Peter Zijlstra To: "Kirill A. Shutemov" Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "Rafael J. Wysocki" , Adrian Hunter , Kuppuswamy Sathyanarayanan , Elena Reshetova , Jun Nakajima , Rick Edgecombe , Tom Lendacky , "Kalra, Ashish" , Sean Christopherson , "Huang, Kai" , Baoquan He , kexec@lists.infradead.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCHv3 06/14] x86/kexec: Keep CR4.MCE set during kexec for TDX guest Message-ID: <20231115122343.GA8262@noisy.programming.kicks-ass.net> References: <20231115120044.8034-1-kirill.shutemov@linux.intel.com> <20231115120044.8034-7-kirill.shutemov@linux.intel.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231115120044.8034-7-kirill.shutemov@linux.intel.com> On Wed, Nov 15, 2023 at 03:00:36PM +0300, Kirill A. Shutemov wrote: > TDX guests are not allowed to clear CR4.MCE. Attempt to clear it leads > to #VE. > > Use alternatives to keep the flag during kexec for TDX guests. > > The change doesn't affect non-TDX-guest environments. > > Signed-off-by: Kirill A. Shutemov > Reviewed-by: Kai Huang > --- > arch/x86/kernel/relocate_kernel_64.S | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S > index 56cab1bb25f5..bea89814b48e 100644 > --- a/arch/x86/kernel/relocate_kernel_64.S > +++ b/arch/x86/kernel/relocate_kernel_64.S > @@ -145,11 +145,16 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) > * Set cr4 to a known state: > * - physical address extension enabled > * - 5-level paging, if it was enabled before > + * - Machine check exception on TDX guest. Clearing MCE is not allowed > + * in TDX guests. > */ > movl $X86_CR4_PAE, %eax > testq $X86_CR4_LA57, %r13 > jz 1f > orl $X86_CR4_LA57, %eax > +1: > + ALTERNATIVE "jmp 1f", "", X86_FEATURE_TDX_GUEST > + orl $X86_CR4_MCE, %eax > 1: ALTERNATIVE "", "orl $X86_CR4_MCE, %eax", X86_FEATURE_TDX_GUEST ? > movq %rax, %cr4 > > -- > 2.41.0 >