linux-kernel - [RFC PATCH v5 023/104] x86/cpu: Add helper functions to allocate/free MKTME keyid

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Date:   Fri,  4 Mar 2022 11:48:39 -0800
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: [RFC PATCH v5 023/104] x86/cpu: Add helper functions to allocate/free MKTME keyid

From: Isaku Yamahata <isaku.yamahata@...el.com>

MKTME keyid is assigned to guest TD.  The memory controller encrypts guest
TD memory with key id.  Add helper functions to allocate/free MKTME keyid
so that TDX KVM assign keyid.

Also export MKTME global keyid that is used to encrypt TDX module and its
memory.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/include/asm/tdx.h |  6 ++++++
 arch/x86/virt/vmx/tdx.c    | 33 ++++++++++++++++++++++++++++++++-
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 9a8dc6afcb63..73bb472bd515 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -139,6 +139,9 @@ int tdx_detect(void);
 int tdx_init(void);
 bool platform_has_tdx(void);
 const struct tdsysinfo_struct *tdx_get_sysinfo(void);
+u32 tdx_get_global_keyid(void);
+int tdx_keyid_alloc(void);
+void tdx_keyid_free(int keyid);
 #else
 static inline void tdx_detect_cpu(struct cpuinfo_x86 *c) { }
 static inline int tdx_detect(void) { return -ENODEV; }
@@ -146,6 +149,9 @@ static inline int tdx_init(void) { return -ENODEV; }
 static inline bool platform_has_tdx(void) { return false; }
 struct tdsysinfo_struct;
 static inline const struct tdsysinfo_struct *tdx_get_sysinfo(void) { return NULL; }
+static inline u32 tdx_get_global_keyid(void) { return 0; };
+static inline int tdx_keyid_alloc(void) { return -EOPNOTSUPP; }
+static inline void tdx_keyid_free(int keyid) { }
 #endif /* CONFIG_INTEL_TDX_HOST */
 
 #endif /* !__ASSEMBLY__ */
diff --git a/arch/x86/virt/vmx/tdx.c b/arch/x86/virt/vmx/tdx.c
index e45f188479cb..d714106321d4 100644
--- a/arch/x86/virt/vmx/tdx.c
+++ b/arch/x86/virt/vmx/tdx.c
@@ -113,7 +113,13 @@ static int tdx_cmr_num;
 static struct tdsysinfo_struct tdx_sysinfo;
 
 /* TDX global KeyID to protect TDX metadata */
-static u32 tdx_global_keyid;
+static u32 __read_mostly tdx_global_keyid;
+
+u32 tdx_get_global_keyid(void)
+{
+	return tdx_global_keyid;
+}
+EXPORT_SYMBOL_GPL(tdx_get_global_keyid);
 
 static bool enable_tdx_host;
 
@@ -189,6 +195,31 @@ static void detect_seam(struct cpuinfo_x86 *c)
 		detect_seam_ap(c);
 }
 
+/* TDX KeyID pool */
+static DEFINE_IDA(tdx_keyid_pool);
+
+int tdx_keyid_alloc(void)
+{
+	if (WARN_ON_ONCE(!tdx_keyid_start || !tdx_keyid_num))
+		return -EINVAL;
+
+	/* The first keyID is reserved for the global key. */
+	return ida_alloc_range(&tdx_keyid_pool, tdx_keyid_start + 1,
+			       tdx_keyid_start + tdx_keyid_num - 1,
+			       GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(tdx_keyid_alloc);
+
+void tdx_keyid_free(int keyid)
+{
+	/* keyid = 0 is reserved. */
+	if (!keyid || keyid <= 0)
+		return;
+
+	ida_free(&tdx_keyid_pool, keyid);
+}
+EXPORT_SYMBOL_GPL(tdx_keyid_free);
+
 static void detect_tdx_keyids_bsp(struct cpuinfo_x86 *c)
 {
 	u64 keyid_part;
-- 
2.25.1