[PATCH v15 012/115] KVM: TDX: Retry SEAMCALL on the lack of entropy error

[isaku . yamahata]

From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

Some SEAMCALL may return TDX_RND_NO_ENTROPY error when the entropy is
lacking.  Retry SEAMCALL on the error following rdrand_long() to retry
RDRAND_RETRY_LOOPS times.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
 arch/x86/kvm/vmx/tdx_errno.h | 1 +
 arch/x86/kvm/vmx/tdx_ops.h   | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/tdx_errno.h b/arch/x86/kvm/vmx/tdx_errno.h
index 56cfd2f558fa..53dc14ba9107 100644
--- a/arch/x86/kvm/vmx/tdx_errno.h
+++ b/arch/x86/kvm/vmx/tdx_errno.h
@@ -14,6 +14,7 @@
 #define TDX_INTERRUPTED_RESUMABLE		0x8000000300000000ULL
 #define TDX_OPERAND_INVALID			0xC000010000000000ULL
 #define TDX_OPERAND_BUSY			0x8000020000000000ULL
+#define TDX_RND_NO_ENTROPY			0x8000020300000000ULL
 #define TDX_VCPU_NOT_ASSOCIATED			0x8000070200000000ULL
 #define TDX_KEY_GENERATION_FAILED		0x8000080000000000ULL
 #define TDX_KEY_STATE_INCORRECT			0xC000081100000000ULL
diff --git a/arch/x86/kvm/vmx/tdx_ops.h b/arch/x86/kvm/vmx/tdx_ops.h
index 76eddecdca12..d588a5507f5a 100644
--- a/arch/x86/kvm/vmx/tdx_ops.h
+++ b/arch/x86/kvm/vmx/tdx_ops.h
@@ -6,6 +6,7 @@
 
 #include <linux/compiler.h>
 
+#include <asm/archrandom.h>
 #include <asm/cacheflush.h>
 #include <asm/asm.h>
 #include <asm/kvm_host.h>
@@ -17,9 +18,14 @@
 static inline u64 tdx_seamcall(u64 op, u64 rcx, u64 rdx, u64 r8, u64 r9,
 			       struct tdx_module_output *out)
 {
+	int retry;
 	u64 ret;
 
-	ret = __seamcall(op, rcx, rdx, r8, r9, out);
+	/* Mimic the existing rdrand_long() to retry RDRAND_RETRY_LOOPS times. */
+	retry = RDRAND_RETRY_LOOPS;
+	do {
+		ret = __seamcall(op, rcx, rdx, r8, r9, out);
+	} while (unlikely(ret == TDX_RND_NO_ENTROPY) && --retry);
 	if (unlikely(ret == TDX_SEAMCALL_UD)) {
 		/*
 		 * SEAMCALLs fail with TDX_SEAMCALL_UD returned when VMX is off.
-- 
2.25.1