write in 30M

hc

2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc

 kernel/arch/x86/include/asm/virtext.h
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@@ -95,12 +95,6 @@
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 		return 0;
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 	}
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-	if (boot_cpu_data.extended_cpuid_level < SVM_CPUID_FUNC) {
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-		if (msg)
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-			*msg = "can't execute cpuid_8000000a";
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-		return 0;
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-	}
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-
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 	if (!boot_cpu_has(X86_FEATURE_SVM)) {
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 		if (msg)
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 			*msg = "svm not available";
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@@ -120,7 +114,21 @@
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 	wrmsrl(MSR_VM_HSAVE_PA, 0);
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 	rdmsrl(MSR_EFER, efer);
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-	wrmsrl(MSR_EFER, efer & ~EFER_SVME);
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+	if (efer & EFER_SVME) {
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+		/*
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+		 * Force GIF=1 prior to disabling SVM to ensure INIT and NMI
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+		 * aren't blocked, e.g. if a fatal error occurred between CLGI
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+		 * and STGI.  Note, STGI may #UD if SVM is disabled from NMI
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+		 * context between reading EFER and executing STGI.  In that
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+		 * case, GIF must already be set, otherwise the NMI would have
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+		 * been blocked, so just eat the fault.
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+		 */
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+		asm_volatile_goto("1: stgi\n\t"
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+				  _ASM_EXTABLE(1b, %l[fault])
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+				  ::: "memory" : fault);
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+fault:
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+		wrmsrl(MSR_EFER, efer & ~EFER_SVME);
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+	}
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 }
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 /** Makes sure SVM is disabled, if it is supported on the CPU