[7/7] kvm x86: report 1GB page support to userspace

Commit Message

Joerg Roedel April 24, 2009, 11:58 a.m. UTC

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 <[e-mail]>
---
 arch/x86/include/asm/kvm_host.h |    2 ++
 arch/x86/kvm/svm.c              |    7 +++++++
 arch/x86/kvm/vmx.c              |    7 +++++++
 arch/x86/kvm/x86.c              |    6 +++++-
 include/linux/kvm.h             |    1 +
 5 files changed, 22 insertions(+), 1 deletions(-)

Comments

Avi Kivity April 28, 2009, 10:10 a.m. UTC | #1

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

Why not do everything via KVM_GET_SUPPORTED_CPUID2 and virtualized 
cpuid?  We can enable it in the kernel unconditionally.

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6215d10..6318d22 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -524,6 +524,8 @@  struct kvm_x86_ops {
 	int (*set_tss_addr)(struct kvm *kvm, unsigned int addr);
 	int (*get_tdp_level)(void);
 	int (*get_mt_mask_shift)(void);
+
+	bool (*gb_page_enable)(void);
 };
 
 extern struct kvm_x86_ops *kvm_x86_ops;
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 053f3c5..0b641c5 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2622,6 +2622,11 @@  static int svm_get_mt_mask_shift(void)
 	return 0;
 }
 
+static bool svm_gb_page_enable(void)
+{
+	return npt_enabled;
+}
+
 static struct kvm_x86_ops svm_x86_ops = {
 	.cpu_has_kvm_support = has_svm,
 	.disabled_by_bios = is_disabled,
@@ -2679,6 +2684,8 @@  static struct kvm_x86_ops svm_x86_ops = {
 	.set_tss_addr = svm_set_tss_addr,
 	.get_tdp_level = get_npt_level,
 	.get_mt_mask_shift = svm_get_mt_mask_shift,
+
+	.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 c6997c0..a1baf52 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3683,6 +3683,11 @@  static int vmx_get_mt_mask_shift(void)
 	return VMX_EPT_MT_EPTE_SHIFT;
 }
 
+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,
@@ -3738,6 +3743,8 @@  static struct kvm_x86_ops vmx_x86_ops = {
 	.set_tss_addr = vmx_set_tss_addr,
 	.get_tdp_level = get_ept_level,
 	.get_mt_mask_shift = vmx_get_mt_mask_shift,
+
+	.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 8cb8542..dec5af3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1011,7 +1011,7 @@  out:
 
 int kvm_dev_ioctl_check_extension(long ext)
 {
-	int r;
+	int r = 0;
 
 	switch (ext) {
 	case KVM_CAP_IRQCHIP:
@@ -1029,6 +1029,10 @@  int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_ASSIGN_DEV_IRQ:
 		r = 1;
 		break;
+	case KVM_CAP_1GB_PAGES:
+		if (kvm_x86_ops->gb_page_enable())
+			r = 1;
+		break;
 	case KVM_CAP_COALESCED_MMIO:
 		r = KVM_COALESCED_MMIO_PAGE_OFFSET;
 		break;
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 3db5d8d..958c582 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -415,6 +415,7 @@  struct kvm_trace_rec {
 #define KVM_CAP_ASSIGN_DEV_IRQ 29
 /* Another bug in KVM_SET_USER_MEMORY_REGION fixed: */
 #define KVM_CAP_JOIN_MEMORY_REGIONS_WORKS 30
+#define KVM_CAP_1GB_PAGES 31
 
 #ifdef KVM_CAP_IRQ_ROUTING