KVM: report 1GB page support to userspace

If userspace knows that the kernel part supports 1GB pages it can enable
the corresponding cpuid bit so that guests actually use GB pages.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 14 insertions, 1 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 92fc0dab505d..10e718db990b 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2754,6 +2754,11 @@ static const struct trace_print_flags svm_exit_reasons_str[] = {
         { -1, NULL }
 };
 
+static bool svm_gb_page_enable(void)
+{
+        return true;
+}
+
 static struct kvm_x86_ops svm_x86_ops = {
         .cpu_has_kvm_support = has_svm,
         .disabled_by_bios = is_disabled,
@@ -2817,6 +2822,7 @@ static struct kvm_x86_ops svm_x86_ops = {
         .get_mt_mask = svm_get_mt_mask,
 
         .exit_reasons_str = svm_exit_reasons_str,
+        .gb_page_enable = svm_gb_page_enable,
 };
 
 static int __init svm_init(void)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c5aaa1b5fdbe..32e6d2031ba2 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3908,6 +3908,11 @@ static const struct trace_print_flags vmx_exit_reasons_str[] = {
         { -1, NULL }
 };
 
+static bool vmx_gb_page_enable(void)
+{
+        return false;
+}
+
 static struct kvm_x86_ops vmx_x86_ops = {
         .cpu_has_kvm_support = cpu_has_kvm_support,
         .disabled_by_bios = vmx_disabled_by_bios,
@@ -3969,6 +3974,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
         .get_mt_mask = vmx_get_mt_mask,
 
         .exit_reasons_str = vmx_exit_reasons_str,
+        .gb_page_enable = vmx_gb_page_enable,
 };
 
 static int __init vmx_init(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 69de7248083f..fa525d511d92 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1444,6 +1444,7 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
                          u32 index, int *nent, int maxnent)
 {
         unsigned f_nx = is_efer_nx() ? F(NX) : 0;
+        unsigned f_gbpages = kvm_x86_ops->gb_page_enable() ? F(GBPAGES) : 0;
 #ifdef CONFIG_X86_64
         unsigned f_lm = F(LM);
 #else
@@ -1468,7 +1469,7 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
                 F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
                 F(PAT) | F(PSE36) | 0 /* Reserved */ |
                 f_nx | 0 /* Reserved */ | F(MMXEXT) | F(MMX) |
-                F(FXSR) | F(FXSR_OPT) | 0 /* GBPAGES */ | 0 /* RDTSCP */ |
+                F(FXSR) | F(FXSR_OPT) | f_gbpages | 0 /* RDTSCP */ |
                 0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW);
         /* cpuid 1.ecx */
         const u32 kvm_supported_word4_x86_features =