kvm: Setup CPUID for the guest

This patch sets up guest CPUID which is based on host CPUID. Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
2026-09-03 20:21:27 +00:00 · 2015-06-01 16:39:39 +01:00
parent 64f06a2b72
commit 6e5e8b8df6
1 changed files with 202 additions and 0 deletions
@@ -11,6 +11,7 @@
 #include <inttypes.h>
 #include <sys/mman.h>
 #include <stdbool.h>
+#include <assert.h>
 #include <limits.h>
 #include <stdarg.h>
 #include <stdlib.h>
@@ -310,8 +311,209 @@ static inline uint32_t selector_to_base(uint16_t selector)
 	return (uint32_t)selector * 16;
 }

+struct cpuid_regs {
+	uint32_t	eax;
+	uint32_t	ebx;
+	uint32_t	ecx;
+	uint32_t 	edx;
+};
+
+static inline void
+cpuid(struct cpuid_regs *regs)
+{
+	asm("cpuid"
+	    : "=a" (regs->eax),
+	      "=b" (regs->ebx),
+	      "=c" (regs->ecx),
+	      "=d" (regs->edx)
+	    : "0" (regs->eax), "2" (regs->ecx));
+}
+
+static struct kvm_cpuid2 *kvm_cpuid__new(unsigned long nent)
+{
+	struct kvm_cpuid2 *self;
+
+	self		= calloc(1, sizeof(*self) + (sizeof(struct kvm_cpuid_entry2) * nent));
+
+	if (!self)
+		die("out of memory");
+
+	return self;
+}
+
+static void kvm_cpuid__delete(struct kvm_cpuid2 *self)
+{
+	free(self);
+}
+
+#define	MAX_KVM_CPUID_ENTRIES		100
+
+enum {
+	CPUID_GET_VENDOR_ID		= 0x00,
+	CPUID_GET_HIGHEST_EXT_FUNCTION	= 0x80000000,
+};
+
+static uint32_t cpuid_highest_ext_func(void)
+{
+	struct cpuid_regs regs;
+
+	regs	= (struct cpuid_regs) {
+		.eax		= CPUID_GET_HIGHEST_EXT_FUNCTION,
+	};
+	cpuid(&regs);
+	
+	return regs.eax;
+}
+
+static uint32_t cpuid_highest_func(void)
+{
+	struct cpuid_regs regs;
+
+	regs	= (struct cpuid_regs) {
+		.eax		= CPUID_GET_VENDOR_ID,
+	};
+	cpuid(&regs);
+	
+	return regs.eax;
+}
+
+static void setup_cpuid(struct kvm *self)
+{
+	struct kvm_cpuid2 *kvm_cpuid;
+	uint32_t highest_ext;
+	uint32_t function;
+	uint32_t highest;
+	uint32_t ndx = 0;
+
+	kvm_cpuid	= kvm_cpuid__new(MAX_KVM_CPUID_ENTRIES);
+
+	highest		= cpuid_highest_func();
+
+	for (function = 0; function < highest; function++) {
+		/*
+		 * NOTE NOTE NOTE! Functions 0x0b and 0x0d seem to need special
+		 * treatment as per qemu sources but we treat them as regular
+		 * CPUID functions here because they are fairly exotic and the
+		 * Linux kernel is not interested in them during boot up.
+		 */
+		switch (function) {
+		case 0x02: {	/* Processor configuration descriptor */
+			struct cpuid_regs regs;
+			uint32_t times;
+
+			regs	= (struct cpuid_regs) {
+				.eax		= function,
+			};
+			cpuid(&regs);
+
+			kvm_cpuid->entries[ndx++]	= (struct kvm_cpuid_entry2) {
+				.function	= function,
+				.index		= 0,
+				.flags		= KVM_CPUID_FLAG_STATEFUL_FUNC | KVM_CPUID_FLAG_STATE_READ_NEXT,
+				.eax		= regs.eax,
+				.ebx		= regs.ebx,
+				.ecx		= regs.ecx,
+				.edx		= regs.edx,
+			};
+
+			times	= regs.eax & 0xff;	/* AL */
+
+			while (times-- > 0) {
+				regs	= (struct cpuid_regs) {
+					.eax		= function,
+				};
+				cpuid(&regs);
+
+				kvm_cpuid->entries[ndx++]	= (struct kvm_cpuid_entry2) {
+					.function	= function,
+					.index		= 0,
+					.flags		= KVM_CPUID_FLAG_STATEFUL_FUNC,
+					.eax		= regs.eax,
+					.ebx		= regs.ebx,
+					.ecx		= regs.ecx,
+					.edx		= regs.edx,
+				};
+			}
+			break;
+		}
+		case 0x04: {
+			uint32_t index;
+
+			for (index = 0; index < 2; index++) {
+				struct cpuid_regs regs = {
+					.eax		= function,
+					.ecx		= index,
+				};
+				cpuid(&regs);
+
+				kvm_cpuid->entries[ndx++]	= (struct kvm_cpuid_entry2) {
+					.function	= function,
+					.index		= index,
+					.flags		= KVM_CPUID_FLAG_SIGNIFCANT_INDEX,
+					.eax		= regs.eax,
+					.ebx		= regs.ebx,
+					.ecx		= regs.ecx,
+					.edx		= regs.edx,
+				};
+			}
+			break;
+		}
+		default: {
+			struct cpuid_regs regs;
+
+			regs	= (struct cpuid_regs) {
+				.eax		= function,
+			};
+			cpuid(&regs);
+
+			kvm_cpuid->entries[ndx++]	= (struct kvm_cpuid_entry2) {
+				.function	= function,
+				.index		= 0,
+				.flags		= 0,
+				.eax		= regs.eax,
+				.ebx		= regs.ebx,
+				.ecx		= regs.ecx,
+				.edx		= regs.edx,
+			};
+			break;
+		}};
+	}
+
+	highest_ext	= cpuid_highest_ext_func();
+
+	for (function = CPUID_GET_HIGHEST_EXT_FUNCTION; function < highest_ext; function++) {
+		struct cpuid_regs regs;
+
+		regs	= (struct cpuid_regs) {
+			.eax		= function,
+		};
+		cpuid(&regs);
+
+		kvm_cpuid->entries[ndx++]	= (struct kvm_cpuid_entry2) {
+			.function	= function,
+			.index		= 0,
+			.flags		= 0,
+			.eax		= regs.eax,
+			.ebx		= regs.ebx,
+			.ecx		= regs.ecx,
+			.edx		= regs.edx,
+		};
+	}
+
+	assert(ndx < MAX_KVM_CPUID_ENTRIES);
+
+	kvm_cpuid->nent		= ndx;
+
+	if (ioctl(self->vcpu_fd, KVM_SET_CPUID2, kvm_cpuid) < 0)
+		die_perror("KVM_SET_CPUID2 failed");
+
+	kvm_cpuid__delete(kvm_cpuid);
+}
+
 void kvm__reset_vcpu(struct kvm *self)
 {
+	setup_cpuid(self);
+
 	self->sregs = (struct kvm_sregs) {
 		.cr0		= 0x60000010ULL,
 		.cs		= (struct kvm_segment) {