linux-kernel - [PATCH v18 015/121] KVM: TDX: Retry SEAMCALL on the lack of entropy error

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Date: Mon, 22 Jan 2024 15:52:51 -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>,
	erdemaktas@...gle.com,
	Sean Christopherson <seanjc@...gle.com>,
	Sagi Shahar <sagis@...gle.com>,
	Kai Huang <kai.huang@...el.com>,
	chen.bo@...el.com,
	hang.yuan@...el.com,
	tina.zhang@...el.com
Subject: [PATCH v18 015/121] KVM: TDX: Retry SEAMCALL on the lack of entropy error

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

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@...el.com>
---
v18:
- update to use struct tdx_modules_args for inputs.
---
 arch/x86/kvm/vmx/tdx_errno.h |  1 +
 arch/x86/kvm/vmx/tdx_ops.h   | 15 +++++++++++----
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/tdx_errno.h b/arch/x86/kvm/vmx/tdx_errno.h
index 7f96696b8e7c..bb093e292fef 100644
--- a/arch/x86/kvm/vmx/tdx_errno.h
+++ b/arch/x86/kvm/vmx/tdx_errno.h
@@ -14,6 +14,7 @@
 #define TDX_OPERAND_INVALID			0xC000010000000000ULL
 #define TDX_OPERAND_BUSY			0x8000020000000000ULL
 #define TDX_PREVIOUS_TLB_EPOCH_BUSY		0x8000020100000000ULL
+#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 0e26cf22240e..f4c16e5265f0 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>
@@ -17,14 +18,20 @@
 static inline u64 tdx_seamcall(u64 op, struct tdx_module_args *in,
 			       struct tdx_module_args *out)
 {
+	struct tdx_module_args args;
+	int retry;
 	u64 ret;
 
-	if (out) {
+	if (!out)
+		out = &args;
+
+	/* Mimic the existing rdrand_long() to retry RDRAND_RETRY_LOOPS times. */
+	retry = RDRAND_RETRY_LOOPS;
+	do {
+		/* As __seamcall_ret() overwrites out, init out on each loop. */
 		*out = *in;
 		ret = __seamcall_ret(op, out);
-	} else
-		ret = __seamcall(op, in);
-
+	} 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