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Message-ID: <20231115130306.kmhaqsfpzi3gkpik@box.shutemov.name>
Date: Wed, 15 Nov 2023 16:03:06 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"Rafael J. Wysocki" <rafael@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
Elena Reshetova <elena.reshetova@...el.com>,
Jun Nakajima <jun.nakajima@...el.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Tom Lendacky <thomas.lendacky@....com>,
"Kalra, Ashish" <ashish.kalra@....com>,
Sean Christopherson <seanjc@...gle.com>,
"Huang, Kai" <kai.huang@...el.com>, Baoquan He <bhe@...hat.com>,
kexec@...ts.infradead.org, linux-coco@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 06/14] x86/kexec: Keep CR4.MCE set during kexec for TDX
guest
On Wed, Nov 15, 2023 at 01:23:43PM +0100, Peter Zijlstra wrote:
> 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 <kirill.shutemov@...ux.intel.com>
> > Reviewed-by: Kai Huang <kai.huang@...el.com>
> > ---
> > 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
>
> ?
Oh. Right. Silly me.
Will fix.
--
Kiryl Shutsemau / Kirill A. Shutemov
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