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Message-ID: <2c76fa83b154566e49425e3a7ccc9a268318d63a.camel@intel.com>
Date: Mon, 9 Oct 2023 12:30:55 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
CC: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
"Reshetova, Elena" <elena.reshetova@...el.com>,
"Nakajima, Jun" <jun.nakajima@...el.com>,
"rafael@...nel.org" <rafael@...nel.org>,
"peterz@...radead.org" <peterz@...radead.org>,
"sathyanarayanan.kuppuswamy@...ux.intel.com"
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
"Hunter, Adrian" <adrian.hunter@...el.com>,
"thomas.lendacky@....com" <thomas.lendacky@....com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>
Subject: Re: [PATCH 05/13] x86/kexec: Keep CR4.MCE set during kexec for TDX
guest
On Thu, 2023-10-05 at 16:13 +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 environments.
Nit: 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:
> movq %rax, %cr4
>
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