linux-kernel - Re: [PATCH v2 2/2] x86/cpu/intel: Detect TME keyid bits before setting MTRR mask registers

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Date: Thu, 1 Feb 2024 10:34:48 +0200
From: "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	Zixi Chen <zixchen@...hat.com>, Adam Dunlap <acdunlap@...gle.com>, 
	Xiaoyao Li <xiaoyao.li@...el.com>, Kai Huang <kai.huang@...el.com>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...nel.org>, x86@...nel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 2/2] x86/cpu/intel: Detect TME keyid bits before
 setting MTRR mask registers

On Thu, Feb 01, 2024 at 12:09:02AM +0100, Paolo Bonzini wrote:
> MKTME repurposes the high bit of physical address to key id for encryption
> key and, even though MAXPHYADDR in CPUID[0x80000008] remains the same,
> the valid bits in the MTRR mask register are based on the reduced number
> of physical address bits.
> 
> detect_tme() in arch/x86/kernel/cpu/intel.c detects TME and subtracts
> it from the total usable physical bits, but it is called too late.
> Move the call to early_init_intel() so that it is called in setup_arch(),
> before MTRRs are setup.
> 
> This fixes boot on TDX-enabled systems, which until now only worked with
> "disable_mtrr_cleanup".  Without the patch, the values written to the
> MTRRs mask registers were 52-bit wide (e.g. 0x000fffff_80000800) and
> the writes failed; with the patch, the values are 46-bit wide, which
> matches the reduced MAXPHYADDR that is shown in /proc/cpuinfo.
> 
> Reported-by: Zixi Chen <zixchen@...hat.com>
> Cc: Adam Dunlap <acdunlap@...gle.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Xiaoyao Li <xiaoyao.li@...el.com>
> Cc: Kai Huang <kai.huang@...el.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: x86@...nel.org
> Cc: stable@...r.kernel.org
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov