linux-kernel - [PATCH v4 06/11] x86/tdx: Get TD execution environment information via TDINFO

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Message-Id: <20210720004057.2112666-7-sathyanarayanan.kuppuswamy@linux.intel.com>
Date:   Mon, 19 Jul 2021 17:40:52 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Cc:     Peter H Anvin <hpa@...or.com>, Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 06/11] x86/tdx: Get TD execution environment information via TDINFO

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

Per Guest-Host-Communication Interface (GHCI) for Intel Trust
Domain Extensions (Intel TDX) specification, sec 2.4.2,
TDCALL[TDINFO] provides basic TD execution environment information, not
provided by CPUID.

Call TDINFO during early boot to be used for following system
initialization.

The call provides info on which bit in pfn is used to indicate that the
page is shared with the host and attributes of the TD, such as debug.

Information about the number of CPUs need not be saved because there are
no users so far for it.

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

Changes since v3:
 * None

 arch/x86/kernel/tdx.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index e81dc66c132e..5d05c77cd85b 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -8,6 +8,14 @@
 
 #include <asm/tdx.h>
 
+/* TDX Module call Leaf IDs */
+#define TDINFO				1
+
+static struct {
+	unsigned int gpa_width;
+	unsigned long attributes;
+} td_info __ro_after_init;
+
 /*
  * Wrapper for standard use of __tdx_hypercall with BUG_ON() check
  * for TDCALL error.
@@ -58,6 +66,19 @@ bool tdx_prot_guest_has(unsigned long flag)
 }
 EXPORT_SYMBOL_GPL(tdx_prot_guest_has);
 
+static void tdg_get_info(void)
+{
+	u64 ret;
+	struct tdx_module_output out = {0};
+
+	ret = __tdx_module_call(TDINFO, 0, 0, 0, 0, &out);
+
+	BUG_ON(ret);
+
+	td_info.gpa_width = out.rcx & GENMASK(5, 0);
+	td_info.attributes = out.rdx;
+}
+
 void __init tdx_early_init(void)
 {
 	if (!cpuid_has_tdx_guest())
@@ -65,5 +86,7 @@ void __init tdx_early_init(void)
 
 	setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
 
+	tdg_get_info();
+
 	pr_info("Guest initialized\n");
 }
-- 
2.25.1