Messages in this thread Patch in this message | | | Date | Thu, 10 Jun 2021 14:28:06 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v1 03/11] x86/cpufeatures: Add TDX Guest CPU feature |
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On Tue, Jun 01, 2021 at 07:21:28PM -0700, Kuppuswamy Sathyanarayanan wrote: > Add CPU feature detection for Trusted Domain Extensions support. > TDX feature adds capabilities to keep guest register state and > memory isolated from hypervisor. > > For TDX guest platforms, executing CPUID(0x21, 0) will return
I'm assuming that 0 is ECX?
> following values in EAX, EBX, ECX and EDX. > > EAX: Maximum sub-leaf number: 0 > EBX/EDX/ECX: Vendor string: > > EBX = "Inte" > EDX = "lTDX" > ECX = " " > > So when above condition is true, set X86_FEATURE_TDX_GUEST > feature cap bit ^ Fullstop.
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h > index ac37830ae941..dddc3a27cc8a 100644 > --- a/arch/x86/include/asm/cpufeatures.h > +++ b/arch/x86/include/asm/cpufeatures.h > @@ -238,6 +238,7 @@ > #define X86_FEATURE_VMW_VMMCALL ( 8*32+19) /* "" VMware prefers VMMCALL hypercall instruction */ > #define X86_FEATURE_PVUNLOCK ( 8*32+20) /* "" PV unlock function */ > #define X86_FEATURE_VCPUPREEMPT ( 8*32+21) /* "" PV vcpu_is_preempted function */ > +#define X86_FEATURE_TDX_GUEST ( 8*32+22) /* Trusted Domain Extensions Guest */
What's the name of the feature bit? "TDX guest"? Why not only X86_FEATURE_TDX and then you can have "tdx" in cpuinfo?
> > /* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */ > #define X86_FEATURE_FSGSBASE ( 9*32+ 0) /* RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/ > diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h > new file mode 100644 > index 000000000000..679500e807f3 > --- /dev/null > +++ b/arch/x86/include/asm/tdx.h > @@ -0,0 +1,20 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* Copyright (C) 2020 Intel Corporation */ > +#ifndef _ASM_X86_TDX_H > +#define _ASM_X86_TDX_H > + > +#define TDX_CPUID_LEAF_ID 0x21 > + > +#ifdef CONFIG_INTEL_TDX_GUEST > + > +#include <asm/cpufeature.h>
As before - put the include at the top.
> +void __init tdx_early_init(void); > + > +#else // !CONFIG_INTEL_TDX_GUEST
No need for that // - comment
> diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c > new file mode 100644 > index 000000000000..5b14b72e41c5 > --- /dev/null > +++ b/arch/x86/kernel/tdx.c > @@ -0,0 +1,30 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (C) 2020 Intel Corporation */ > + > +#include <asm/tdx.h> > + > +static inline bool cpuid_has_tdx_guest(void) > +{ > + u32 eax, signature[3]; Shorten that array name to "sig" so that you don't have to break the cpuid_count() line below.
> + > + if (cpuid_eax(0) < TDX_CPUID_LEAF_ID) > + return false; > + > + cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &signature[0], > + &signature[1], &signature[2]); > + > + if (memcmp("IntelTDX ", signature, 12)) > + return false; > + > + return true;
or simply:
return !memcmp(...
> +} > + > +void __init tdx_early_init(void) > +{ > + if (!cpuid_has_tdx_guest()) > + return; > + > + setup_force_cpu_cap(X86_FEATURE_TDX_GUEST); > + > + pr_info("TDX guest is initialized\n");
Use pr_fmt in this file:
#undef pr_fmt #define pr_fmt(fmt) "x86/tdx: " fmt
and then do
pr_info("Guest initialized\n");
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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