[PATCH v2] kvm: vmx: Stop wasting a page for guest_msrs

[Jim Mattson <jmattson@google.com>]

We will never need more guest_msrs than there are indices in
vmx_msr_index. Thus, at present, the guest_msrs array will not exceed
168 bytes.

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
---
v1 -> v2:
  Changed NR_GUEST_MSRS to NR_SHARED_MSRS.
  Added BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) != NR_SHARED_MSRS).

 arch/x86/kvm/vmx/vmx.c | 12 ++----------
 arch/x86/kvm/vmx/vmx.h |  8 +++++++-
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1b9ab4166397d..e3394c839dea6 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6666,7 +6666,6 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
 	free_vpid(vmx->vpid);
 	nested_vmx_free_vcpu(vcpu);
 	free_loaded_vmcs(vmx->loaded_vmcs);
-	kfree(vmx->guest_msrs);
 	kvm_vcpu_uninit(vcpu);
 	kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.user_fpu);
 	kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu);
@@ -6723,12 +6722,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 			goto uninit_vcpu;
 	}
 
-	vmx->guest_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL_ACCOUNT);
-	BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) * sizeof(vmx->guest_msrs[0])
-		     > PAGE_SIZE);
-
-	if (!vmx->guest_msrs)
-		goto free_pml;
+	BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) != NR_SHARED_MSRS);
 
 	for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i) {
 		u32 index = vmx_msr_index[i];
@@ -6760,7 +6754,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 
 	err = alloc_loaded_vmcs(&vmx->vmcs01);
 	if (err < 0)
-		goto free_msrs;
+		goto free_pml;
 
 	msr_bitmap = vmx->vmcs01.msr_bitmap;
 	vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_TSC, MSR_TYPE_R);
@@ -6822,8 +6816,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 
 free_vmcs:
 	free_loaded_vmcs(vmx->loaded_vmcs);
-free_msrs:
-	kfree(vmx->guest_msrs);
 free_pml:
 	vmx_destroy_pml_buffer(vmx);
 uninit_vcpu:
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 7c1b978b2df44..a4f7f737c5d44 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -22,6 +22,12 @@ extern u32 get_umwait_control_msr(void);
 
 #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4))
 
+#ifdef CONFIG_X86_64
+#define NR_SHARED_MSRS	7
+#else
+#define NR_SHARED_MSRS	4
+#endif
+
 #define NR_LOADSTORE_MSRS 8
 
 struct vmx_msrs {
@@ -206,7 +212,7 @@ struct vcpu_vmx {
 	u32                   idt_vectoring_info;
 	ulong                 rflags;
 
-	struct shared_msr_entry *guest_msrs;
+	struct shared_msr_entry guest_msrs[NR_SHARED_MSRS];
 	int                   nmsrs;
 	int                   save_nmsrs;
 	bool                  guest_msrs_ready;
-- 
2.24.0.393.g34dc348eaf-goog