linux-kernel - [PATCH v16 012/116] KVM: TDX: Retry SEAMCALL on the lack of entropy error

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Message-Id: <a026559ffe2f10108c243327462af0bd066ffb5d.1697471314.git.isaku.yamahata@intel.com>
Date:   Mon, 16 Oct 2023 09:13:24 -0700
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>,
        David Matlack <dmatlack@...gle.com>,
        Kai Huang <kai.huang@...el.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, chen.bo@...el.com,
        hang.yuan@...el.com, tina.zhang@...el.com
Subject: [PATCH v16 012/116] 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>
---
 arch/x86/kvm/vmx/tdx_errno.h |  1 +
 arch/x86/kvm/vmx/tdx_ops.h   | 40 +++++++++++++++++++++---------------
 2 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kvm/vmx/tdx_errno.h b/arch/x86/kvm/vmx/tdx_errno.h
index ec76740dc6a1..dbee050b2356 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 12fd6b8d49e0..a55977626ae3 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>
@@ -17,25 +18,30 @@
 static inline u64 tdx_seamcall(u64 op, u64 rcx, u64 rdx, u64 r8, u64 r9,
 			       struct tdx_module_args *out)
 {
+	int retry;
 	u64 ret;
 
-	if (out) {
-		*out = (struct tdx_module_args) {
-			.rcx = rcx,
-			.rdx = rdx,
-			.r8 = r8,
-			.r9 = r9,
-		};
-		ret = __seamcall_ret(op, out);
-	} else {
-		struct tdx_module_args args = {
-			.rcx = rcx,
-			.rdx = rdx,
-			.r8 = r8,
-			.r9 = r9,
-		};
-		ret = __seamcall(op, &args);
-	}
+	/* Mimic the existing rdrand_long() to retry RDRAND_RETRY_LOOPS times. */
+	retry = RDRAND_RETRY_LOOPS;
+	do {
+		if (out) {
+			*out = (struct tdx_module_args) {
+				.rcx = rcx,
+				.rdx = rdx,
+				.r8 = r8,
+				.r9 = r9,
+			};
+			ret = __seamcall_ret(op, out);
+		} else {
+			struct tdx_module_args args = {
+				.rcx = rcx,
+				.rdx = rdx,
+				.r8 = r8,
+				.r9 = r9,
+			};
+			ret = __seamcall(op, &args);
+		}
+	} 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