diff mbox

[v2,2/3] x86/vmx: optimize vmx_read/write_guest_msr()

Message ID 20170217154233.28514-3-sergey.dyasli@citrix.com (mailing list archive)
State New, archived
Headers show

Commit Message

Sergey Dyasli Feb. 17, 2017, 3:42 p.m. UTC 
Replace linear scan with vmx_find_msr().  This way the time complexity
of searching for required MSR reduces from linear to logarithmic.

Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
---
v1 --> v2:
- a new patch, factored out from v1 1/2

 xen/arch/x86/hvm/vmx/vmcs.c | 26 ++++++++------------------
 1 file changed, 8 insertions(+), 18 deletions(-)

Comments

Tian, Kevin Feb. 21, 2017, 9:31 a.m. UTC | #1 
> From: Sergey Dyasli [mailto:sergey.dyasli@citrix.com]
> Sent: Friday, February 17, 2017 11:43 PM
> 
> Replace linear scan with vmx_find_msr().  This way the time complexity
> of searching for required MSR reduces from linear to logarithmic.
> 
> Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>

Acked-by: Kevin Tian <kevin.tian@intel.com>
Jan Beulich Feb. 22, 2017, 10:16 a.m. UTC | #2 
>>> On 17.02.17 at 16:42, <sergey.dyasli@citrix.com> wrote:
> --- a/xen/arch/x86/hvm/vmx/vmcs.c
> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> @@ -1347,17 +1347,12 @@ struct vmx_msr_entry *vmx_find_msr(u32 msr, int type)
>  
>  int vmx_read_guest_msr(u32 msr, u64 *val)
>  {
> -    struct vcpu *curr = current;
> -    unsigned int i, msr_count = curr->arch.hvm_vmx.msr_count;
> -    const struct vmx_msr_entry *msr_area = curr->arch.hvm_vmx.msr_area;
> +    struct vmx_msr_entry *ent;
>  
> -    for ( i = 0; i < msr_count; i++ )
> +    if ( (ent = vmx_find_msr(msr, VMX_GUEST_MSR)) != NULL )

I think this would read better (less parentheses etc) as

    struct vmx_msr_entry *ent = vmx_find_msr(msr, VMX_GUEST_MSR);
 
    if ( ent )

but either way
Reviewed-by: Jan Beulich <jbeulich@suse.com>

Jan
diff mbox

Patch

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 49587d6..6c86147 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1347,17 +1347,12 @@  struct vmx_msr_entry *vmx_find_msr(u32 msr, int type)
 
 int vmx_read_guest_msr(u32 msr, u64 *val)
 {
-    struct vcpu *curr = current;
-    unsigned int i, msr_count = curr->arch.hvm_vmx.msr_count;
-    const struct vmx_msr_entry *msr_area = curr->arch.hvm_vmx.msr_area;
+    struct vmx_msr_entry *ent;
 
-    for ( i = 0; i < msr_count; i++ )
+    if ( (ent = vmx_find_msr(msr, VMX_GUEST_MSR)) != NULL )
     {
-        if ( msr_area[i].index == msr )
-        {
-            *val = msr_area[i].data;
-            return 0;
-        }
+        *val = ent->data;
+        return 0;
     }
 
     return -ESRCH;
@@ -1365,17 +1360,12 @@  int vmx_read_guest_msr(u32 msr, u64 *val)
 
 int vmx_write_guest_msr(u32 msr, u64 val)
 {
-    struct vcpu *curr = current;
-    unsigned int i, msr_count = curr->arch.hvm_vmx.msr_count;
-    struct vmx_msr_entry *msr_area = curr->arch.hvm_vmx.msr_area;
+    struct vmx_msr_entry *ent;
 
-    for ( i = 0; i < msr_count; i++ )
+    if ( (ent = vmx_find_msr(msr, VMX_GUEST_MSR)) != NULL )
     {
-        if ( msr_area[i].index == msr )
-        {
-            msr_area[i].data = val;
-            return 0;
-        }
+        ent->data = val;
+        return 0;
     }
 
     return -ESRCH;