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From: Kuppuswamy Sathyanarayanan  <sathyanarayanan.kuppuswamy@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, Paolo Bonzini <pbonzini@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: [PATCH v6 11/11] x86/tdx: Handle CPUID via #VE
Date: Fri,  3 Sep 2021 10:28:12 -0700	[thread overview]
Message-ID: <20210903172812.1097643-12-sathyanarayanan.kuppuswamy@linux.intel.com> (raw)
In-Reply-To: <20210903172812.1097643-1-sathyanarayanan.kuppuswamy@linux.intel.com>

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

TDX has three classes of CPUID leaves: some CPUID leaves are always
handled by the CPU, others are handled by the TDX module, and some
others are handled by the VMM. Since the VMM cannot directly intercept
the instruction these are reflected with a #VE exception to the guest,
which then converts it into a hypercall to the VMM, or handled
directly.

The TDX module specification [1], sec 16.2 has a full list of CPUID
leaves which are handled natively or by the TDX module. Only unknown
CPUIDs are handled by the #VE method. In practice this typically only
applies to the hypervisor-specific CPUIDs unknown to the native CPU.

Therefore there is no risk of causing this in early CPUID code which
runs before the #VE handler is set up because it will never access
those exotic CPUID leaves.

[1] - https://software.intel.com/content/dam/develop/external/us/en/documents/tdx-module-1.0-public-spec-v0.931.pdf

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---

Changes since v5:
 * Fixed commit log as per review comments.
 * Removed WARN_ON() in tdx_handle_cpuid().
 * Renamed "tdg" prefix with "tdx".

Changes since v4:
 * None

Changes since v3:
 * None
 arch/x86/kernel/tdx.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 5c52dde4a5fd..c65c117aff5f 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -150,6 +150,21 @@ static int tdx_write_msr_safe(unsigned int msr, unsigned int low,
 	return ret ? -EIO : 0;
 }
 
+static u64 tdx_handle_cpuid(struct pt_regs *regs)
+{
+	struct tdx_hypercall_output out = {0};
+	u64 ret;
+
+	ret = _tdx_hypercall(EXIT_REASON_CPUID, regs->ax, regs->cx, 0, 0, &out);
+
+	regs->ax = out.r12;
+	regs->bx = out.r13;
+	regs->cx = out.r14;
+	regs->dx = out.r15;
+
+	return ret;
+}
+
 unsigned long tdx_get_ve_info(struct ve_info *ve)
 {
 	struct tdx_module_output out = {0};
@@ -193,6 +208,9 @@ int tdx_handle_virtualization_exception(struct pt_regs *regs,
 	case EXIT_REASON_MSR_WRITE:
 		ret = tdx_write_msr_safe(regs->cx, regs->ax, regs->dx);
 		break;
+	case EXIT_REASON_CPUID:
+		ret = tdx_handle_cpuid(regs);
+		break;
 	default:
 		pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
 		return -EFAULT;
-- 
2.25.1


  parent reply	other threads:[~2021-09-03 17:29 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-03 17:28 [PATCH v6 00/11] Add TDX Guest Support (Initial support) Kuppuswamy Sathyanarayanan
2021-09-03 17:28 ` [PATCH v6 01/11] x86/paravirt: Move halt paravirt calls under CONFIG_PARAVIRT Kuppuswamy Sathyanarayanan
2021-09-03 18:22   ` Borislav Petkov
2021-09-03 19:03     ` Kuppuswamy, Sathyanarayanan
2021-09-03 20:33       ` Borislav Petkov
2021-09-03 17:28 ` [PATCH v6 02/11] x86/tdx: Introduce INTEL_TDX_GUEST config option Kuppuswamy Sathyanarayanan
2021-09-28 11:37   ` Joerg Roedel
2021-09-28 12:52     ` Kuppuswamy, Sathyanarayanan
2021-09-03 17:28 ` [PATCH v6 03/11] x86/cpufeatures: Add TDX Guest CPU feature Kuppuswamy Sathyanarayanan
2021-09-28 11:39   ` Joerg Roedel
2021-09-28 12:53     ` Kuppuswamy, Sathyanarayanan
2021-09-03 17:28 ` [PATCH v6 04/11] x86/tdx: Add protected guest support for TDX guest Kuppuswamy Sathyanarayanan
2021-09-28 11:46   ` Joerg Roedel
2021-09-28 12:56     ` Kuppuswamy, Sathyanarayanan
2021-09-28 13:04       ` Joerg Roedel
2021-09-28 13:18         ` Borislav Petkov
2021-09-03 17:28 ` [PATCH v6 05/11] x86/tdx: Add __tdx_module_call() and __tdx_hypercall() helper functions Kuppuswamy Sathyanarayanan
2021-09-03 17:28 ` [PATCH v6 06/11] x86/traps: Add #VE support for TDX guest Kuppuswamy Sathyanarayanan
2021-09-28 12:16   ` Joerg Roedel
2021-09-28 14:05     ` Dave Hansen
2021-09-28 15:22       ` Joerg Roedel
2021-09-28 15:25         ` Dave Hansen
2021-09-28 15:23   ` Dave Hansen
2021-09-28 16:59     ` Kuppuswamy, Sathyanarayanan
2021-09-03 17:28 ` [PATCH v6 07/11] x86/tdx: Add HLT " Kuppuswamy Sathyanarayanan
2021-09-03 17:28 ` [PATCH v6 08/11] x86/tdx: Wire up KVM hypercalls Kuppuswamy Sathyanarayanan
2021-09-03 17:28 ` [PATCH v6 09/11] x86/tdx: Add MSR support for TDX guest Kuppuswamy Sathyanarayanan
2021-09-03 17:28 ` [PATCH v6 10/11] x86/tdx: Don't write CSTAR MSR on Intel Kuppuswamy Sathyanarayanan
2021-09-03 17:28 ` Kuppuswamy Sathyanarayanan [this message]
2021-09-03 18:35   ` [PATCH v6 11/11] x86/tdx: Handle CPUID via #VE Dave Hansen
2021-09-03 19:14     ` Kuppuswamy, Sathyanarayanan
2021-09-03 23:43       ` Sean Christopherson
2021-09-03 23:54         ` Andi Kleen
2021-09-04  0:00           ` Dave Hansen
2021-09-04  0:05             ` Andi Kleen

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