[PATCH] KVM: Refactor and simplify kvm_dev_ioctl_get_supported_cpuid

[Sasha Levin <levinsasha928@xxxxxxxxx>]

This patch cleans and simplifies kvm_dev_ioctl_get_supported_cpuid by using a table
instead of duplicating code as Avi suggested.

This patch also fixes a bug where kvm_dev_ioctl_get_supported_cpuid would return
-E2BIG when amount of entries passed was just right.

Cc: Avi Kivity <avi@xxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
---
 arch/x86/kvm/cpuid.c |   78 ++++++++++++++++++++++---------------------------
 1 files changed, 35 insertions(+), 43 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index bbaa6d8..c9ede4d 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -425,12 +425,31 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 
 #undef F
 
+struct kvm_cpuid_param {
+	u32 func;
+	u32 idx;
+	u32 leaves;
+	int (*qualifier)(struct kvm_cpuid_param *param);
+};
+
+int is_centaur_cpu(struct kvm_cpuid_param *param)
+{
+	return boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR;
+}
+
 int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
 				      struct kvm_cpuid_entry2 __user *entries)
 {
 	struct kvm_cpuid_entry2 *cpuid_entries;
-	int limit, nent = 0, r = -E2BIG;
+	int limit, nent = 0, r = -E2BIG, i;
 	u32 func;
+	struct kvm_cpuid_param param[] = {
+		{ .func = 0, .leaves = 1 },
+		{ .func = 0x80000000, .leaves = 1 },
+		{ .func = 0xC0000000, .qualifier = is_centaur_cpu, .leaves = 1 },
+		{ .func = KVM_CPUID_SIGNATURE },
+		{ .func = KVM_CPUID_FEATURES },
+	};
 
 	if (cpuid->nent < 1)
 		goto out;
@@ -441,59 +460,32 @@ int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
 	if (!cpuid_entries)
 		goto out;
 
-	do_cpuid_ent(&cpuid_entries[0], 0, 0, &nent, cpuid->nent);
-	limit = cpuid_entries[0].eax;
-	for (func = 1; func <= limit && nent < cpuid->nent; ++func)
-		do_cpuid_ent(&cpuid_entries[nent], func, 0,
-			     &nent, cpuid->nent);
-	r = -E2BIG;
-	if (nent >= cpuid->nent)
-		goto out_free;
-
-	do_cpuid_ent(&cpuid_entries[nent], 0x80000000, 0, &nent, cpuid->nent);
-	limit = cpuid_entries[nent - 1].eax;
-	for (func = 0x80000001; func <= limit && nent < cpuid->nent; ++func)
-		do_cpuid_ent(&cpuid_entries[nent], func, 0,
-			     &nent, cpuid->nent);
-
+	for (i = 0; i < ARRAY_SIZE(param); i++) {
+		struct kvm_cpuid_param *ent = &param[i];
 
+		if (ent->qualifier && !ent->qualifier(ent))
+			continue;
 
-	r = -E2BIG;
-	if (nent >= cpuid->nent)
-		goto out_free;
+		if (nent >= cpuid->nent)
+			break;
 
-	/* Add support for Centaur's CPUID instruction. */
-	if (boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR) {
-		do_cpuid_ent(&cpuid_entries[nent], 0xC0000000, 0,
+		do_cpuid_ent(&cpuid_entries[nent], ent->func, ent->idx,
 				&nent, cpuid->nent);
 
-		r = -E2BIG;
-		if (nent >= cpuid->nent)
-			goto out_free;
+		if (!ent->leaves)
+			continue;
 
 		limit = cpuid_entries[nent - 1].eax;
-		for (func = 0xC0000001;
-			func <= limit && nent < cpuid->nent; ++func)
-			do_cpuid_ent(&cpuid_entries[nent], func, 0,
-					&nent, cpuid->nent);
+		for (func = ent->func + 1; func <= limit && nent < cpuid->nent; ++func)
+			do_cpuid_ent(&cpuid_entries[nent], func, ent->idx,
+				     &nent, cpuid->nent);
 
-		r = -E2BIG;
-		if (nent >= cpuid->nent)
-			goto out_free;
+		if (func <= limit)
+			break;
 	}
 
-	do_cpuid_ent(&cpuid_entries[nent], KVM_CPUID_SIGNATURE, 0, &nent,
-		     cpuid->nent);
-
-	r = -E2BIG;
-	if (nent >= cpuid->nent)
-		goto out_free;
-
-	do_cpuid_ent(&cpuid_entries[nent], KVM_CPUID_FEATURES, 0, &nent,
-		     cpuid->nent);
-
 	r = -E2BIG;
-	if (nent >= cpuid->nent)
+	if (i < ARRAY_SIZE(param) || nent > cpuid->nent)
 		goto out_free;
 
 	r = -EFAULT;
-- 
1.7.8.rc3

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