[PATCH v12 06/22] x86/virt/tdx: Handle SEAMCALL running out of entropy error

[Kai Huang <kai.huang@intel.com>]

Some SEAMCALLs use the RDRAND hardware and can fail for the same reasons
as RDRAND.  Use the kernel RDRAND retry logic for them.

Signed-off-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---

v11 -> v12:
 - Added tags from Dave/Kirill/David.
 - Improved changelog (Dave).
 - Slight code improvement (David)
   - Initialize retry directly when declaring it.
   - Simplify comment around mimic rdrand_long().

v10 -> v11:
 - New patch

---
 arch/x86/virt/vmx/tdx/tdx.c | 16 ++++++++++++++--
 arch/x86/virt/vmx/tdx/tdx.h | 17 +++++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index f8233cba5931..141d12376c4d 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -15,6 +15,7 @@
 #include <linux/smp.h>
 #include <asm/msr-index.h>
 #include <asm/msr.h>
+#include <asm/archrandom.h>
 #include <asm/tdx.h>
 #include "tdx.h"
 
@@ -32,12 +33,23 @@ static int __always_unused seamcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
 				    u64 *seamcall_ret,
 				    struct tdx_module_output *out)
 {
+	int cpu, retry = RDRAND_RETRY_LOOPS;
 	u64 sret;
-	int cpu;
 
 	/* Need a stable CPU id for printing error message */
 	cpu = get_cpu();
-	sret = __seamcall(fn, rcx, rdx, r8, r9, out);
+
+	/*
+	 * Certain SEAMCALL leaf functions may return error due to
+	 * running out of entropy, in which case the SEAMCALL should
+	 * be retried.  Handle this in SEAMCALL common function.
+	 *
+	 * Mimic rdrand_long() retry behavior.
+	 */
+	do {
+		sret = __seamcall(fn, rcx, rdx, r8, r9, out);
+	} while (sret == TDX_RND_NO_ENTROPY && --retry);
+
 	put_cpu();
 
 	/* Save SEAMCALL return code if the caller wants it */
diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
index 48ad1a1ba737..55dbb1b8c971 100644
--- a/arch/x86/virt/vmx/tdx/tdx.h
+++ b/arch/x86/virt/vmx/tdx/tdx.h
@@ -4,6 +4,23 @@
 
 #include <linux/types.h>
 
+/*
+ * This file contains both macros and data structures defined by the TDX
+ * architecture and Linux defined software data structures and functions.
+ * The two should not be mixed together for better readability.  The
+ * architectural definitions come first.
+ */
+
+/*
+ * TDX SEAMCALL error codes
+ */
+#define TDX_RND_NO_ENTROPY	0x8000020300000000ULL
+
+/*
+ * Do not put any hardware-defined TDX structure representations below
+ * this comment!
+ */
+
 struct tdx_module_output;
 u64 __seamcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
 	       struct tdx_module_output *out);
-- 
2.40.1