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From: Thomas Gleixner <tglx@linutronix.de>
To: Kuppuswamy Sathyanarayanan 
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
	David Hildenbrand <david@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Juergen Gross <jgross@suse.com>, Deep Shah <sdeep@vmware.com>,
	VMware Inc <pv-drivers@vmware.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>
Cc: Peter H Anvin <hpa@zytor.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Andi Kleen <ak@linux.intel.com>,
	Kirill Shutemov <kirill.shutemov@linux.intel.com>,
	Sean Christopherson <seanjc@google.com>,
	Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v10 11/11] x86/tdx: Handle CPUID via #VE
Date: Thu, 14 Oct 2021 14:01:06 +0200	[thread overview]
Message-ID: <87a6jb7r3x.ffs@tglx> (raw)
In-Reply-To: <20211009053747.1694419-12-sathyanarayanan.kuppuswamy@linux.intel.com>

On Fri, Oct 08 2021 at 22:37, Kuppuswamy Sathyanarayanan wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>
> When running virtualized, the CPUID instruction is handled differently
> based on the leaf being accessed.  The behavior depends only on the
> leaf and applies equally to both kernel/ring-0 and userspace/ring-3
> execution of CPUID. Historically, there are two basic classes:
>
>  * Leaves handled transparently to the guest
>  * Leaves handled by the VMM
>
> In a typical guest without TDX, "handled by the VMM" leaves cause a
> VMEXIT.  TDX replaces these VMEXITs with a #VE exception in the guest.
> The guest typically handles the #VE by making a hypercall to the VMM.
>
> The TDX module specification [1], section titled "CPUID Virtualization"
> talks about a few more classes of CPUID handling. But, for the purposes
> of this patch, the "handled transparently" CPUID leaves are all lumped
> together because the guest handling is the same.

What means 'for the purposes of this patch'? And I have no idea what's
lumped together means either.

#VE is either raised on CPUID leaf/sub-leaf combinations which are not
part of the CPUID virtualization table or on request of the guest for
all CPUID invocations (either Ring0 or Ring3 or both).

So this patch implements the #VE handling for EXIT_REASON_CPUID by
handing it through to the hypercall, which in turn lets the TDX module
handle it by invoking the host VMM.

So unless the guest requested #VE on all CPUID invocations it won't see
a #VE for the transparent leaf/sub-leaf combinations. #VE is raised
for the VMM handled ones which goes through the hypercall, right?

I must be missing something, but that last paragraph does not make any
sense to me.

Thanks,

        tglx

  reply	other threads:[~2021-10-14 12:01 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-09  5:37 [PATCH v10 00/11] Add TDX Guest Support (Initial support) Kuppuswamy Sathyanarayanan
2021-10-09  5:37 ` [PATCH v10 01/11] x86/paravirt: Move halt paravirt calls under CONFIG_PARAVIRT Kuppuswamy Sathyanarayanan
2021-10-15 16:59   ` David Hildenbrand
2021-10-09  5:37 ` [PATCH v10 02/11] x86/tdx: Introduce INTEL_TDX_GUEST config option Kuppuswamy Sathyanarayanan
2021-10-11 18:19   ` Josh Poimboeuf
2021-10-11 18:38     ` Andi Kleen
2021-10-11 18:47       ` Kuppuswamy, Sathyanarayanan
2021-10-09  5:37 ` [PATCH v10 03/11] x86/cpufeatures: Add TDX Guest CPU feature Kuppuswamy Sathyanarayanan
2021-10-13  8:18   ` Borislav Petkov
2021-10-13 13:32     ` Sathyanarayanan Kuppuswamy
2021-10-13 19:42     ` Josh Poimboeuf
2021-10-13 23:19       ` Thomas Gleixner
2021-10-14  0:25         ` Josh Poimboeuf
2021-10-14  7:57           ` Borislav Petkov
     [not found]       ` <1a6220a5-3abd-dea1-4b2f-2acade311236@linux.intel.com>
2021-10-18 21:59         ` Borislav Petkov
2021-10-18 22:04           ` Sathyanarayanan Kuppuswamy
2021-10-13 20:44   ` Thomas Gleixner
2021-10-13 21:05     ` Sathyanarayanan Kuppuswamy
2021-10-13 21:35       ` Thomas Gleixner
2021-10-13 21:07     ` Borislav Petkov
2021-10-13 21:25       ` Thomas Gleixner
2021-10-13 21:37         ` Borislav Petkov
2021-10-13 22:28           ` Sathyanarayanan Kuppuswamy
2021-10-13 23:02             ` Thomas Gleixner
2021-10-14 17:28               ` Sathyanarayanan Kuppuswamy
2021-10-09  5:37 ` [PATCH v10 04/11] x86/tdx: Add TDX support to intel_cc_platform_has() Kuppuswamy Sathyanarayanan
2021-10-13 15:57   ` Borislav Petkov
2021-10-14  7:12   ` Thomas Gleixner
2021-10-14 17:31     ` Sathyanarayanan Kuppuswamy
2021-10-09  5:37 ` [PATCH v10 05/11] x86/tdx: Add __tdx_module_call() and __tdx_hypercall() helper functions Kuppuswamy Sathyanarayanan
2021-10-14  7:28   ` Thomas Gleixner
2021-10-15  0:19     ` Sathyanarayanan Kuppuswamy
2021-10-09  5:37 ` [PATCH v10 06/11] x86/traps: Add #VE support for TDX guest Kuppuswamy Sathyanarayanan
2021-10-14  8:30   ` Thomas Gleixner
2021-10-17  2:45     ` Sathyanarayanan Kuppuswamy
2021-10-17  3:18       ` Dave Hansen
2021-10-17  3:49         ` Sathyanarayanan Kuppuswamy
2021-10-09  5:37 ` [PATCH v10 07/11] x86/tdx: Add HLT " Kuppuswamy Sathyanarayanan
2021-10-14  9:30   ` Thomas Gleixner
2021-10-15  1:33     ` Sathyanarayanan Kuppuswamy
2021-10-15 15:03       ` Sean Christopherson
2021-10-09  5:37 ` [PATCH v10 08/11] x86/tdx: Wire up KVM hypercalls Kuppuswamy Sathyanarayanan
2021-10-14 10:21   ` Thomas Gleixner
2021-10-15  3:03     ` Sathyanarayanan Kuppuswamy
2021-10-09  5:37 ` [PATCH v10 09/11] x86/tdx: Add MSR support for TDX guest Kuppuswamy Sathyanarayanan
2021-10-09  5:37 ` [PATCH v10 10/11] x86/tdx: Don't write CSTAR MSR on Intel Kuppuswamy Sathyanarayanan
2021-10-14 10:47   ` Thomas Gleixner
2021-10-14 13:47     ` Andi Kleen
2021-10-14 14:27       ` Thomas Gleixner
2021-10-09  5:37 ` [PATCH v10 11/11] x86/tdx: Handle CPUID via #VE Kuppuswamy Sathyanarayanan
2021-10-14 12:01   ` Thomas Gleixner [this message]
2021-10-14 13:25     ` Dave Hansen
2021-10-09  7:38 ` [PATCH v10 00/11] Add TDX Guest Support (Initial support) Borislav Petkov
2021-10-09 20:56   ` Kuppuswamy, Sathyanarayanan
2021-10-11 13:03     ` Borislav Petkov
2021-10-11 16:33       ` Dave Hansen
2021-10-11 16:48         ` Dave Hansen
2021-10-11 17:04           ` Borislav Petkov

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