[v10,02/14] KVM: Cache as_id in kvm_memory_slot
diff mbox series

Message ID 20200601115957.1581250-3-peterx@redhat.com
State New
Headers show
Series
  • KVM: Dirty ring interface
Related show

Commit Message

Peter Xu June 1, 2020, 11:59 a.m. UTC
Cache the address space ID just like the slot ID.  It will be used in
order to fill in the dirty ring entries.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/linux/kvm_host.h | 1 +
 virt/kvm/kvm_main.c      | 1 +
 2 files changed, 2 insertions(+)

Comments

Sean Christopherson July 2, 2020, 11:08 p.m. UTC | #1
On Mon, Jun 01, 2020 at 07:59:45AM -0400, Peter Xu wrote:
> Cache the address space ID just like the slot ID.  It will be used in
> order to fill in the dirty ring entries.
> 
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  include/linux/kvm_host.h | 1 +
>  virt/kvm/kvm_main.c      | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 01276e3d01b9..5e7bbaf7a36b 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -346,6 +346,7 @@ struct kvm_memory_slot {
>  	unsigned long userspace_addr;
>  	u32 flags;
>  	short id;
> +	u16 as_id;
>  };
>  
>  static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memslot)
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 74bdb7bf3295..ebdd98a30e82 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1243,6 +1243,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
>  	if (!mem->memory_size)
>  		return kvm_delete_memslot(kvm, mem, &old, as_id);

This technically needs to set as_id in the deleted memslot.  I highly doubt
it will ever matter from a functionality perspective, but it'd be confusing
to encounter a memslot whose as_id did not match that of its owner.

> +	new.as_id = as_id;
>  	new.id = id;
>  	new.base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
>  	new.npages = mem->memory_size >> PAGE_SHIFT;
> -- 
> 2.26.2
>
Peter Xu July 3, 2020, 6:41 p.m. UTC | #2
On Thu, Jul 02, 2020 at 04:08:49PM -0700, Sean Christopherson wrote:
> On Mon, Jun 01, 2020 at 07:59:45AM -0400, Peter Xu wrote:
> > Cache the address space ID just like the slot ID.  It will be used in
> > order to fill in the dirty ring entries.
> > 
> > Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> > Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >  include/linux/kvm_host.h | 1 +
> >  virt/kvm/kvm_main.c      | 1 +
> >  2 files changed, 2 insertions(+)
> > 
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index 01276e3d01b9..5e7bbaf7a36b 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -346,6 +346,7 @@ struct kvm_memory_slot {
> >  	unsigned long userspace_addr;
> >  	u32 flags;
> >  	short id;
> > +	u16 as_id;
> >  };
> >  
> >  static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memslot)
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 74bdb7bf3295..ebdd98a30e82 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -1243,6 +1243,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
> >  	if (!mem->memory_size)
> >  		return kvm_delete_memslot(kvm, mem, &old, as_id);
> 
> This technically needs to set as_id in the deleted memslot.  I highly doubt
> it will ever matter from a functionality perspective, but it'd be confusing
> to encounter a memslot whose as_id did not match that of its owner.

Yeah it shouldn't matter because as_id is directly passed in to look up the
pointer of kvm_memslots in kvm_delete_memslot, and memslot->as_id shouldn't be
further referenced.

I can add a comment above if this can clarify things a bit:

+	u16 as_id; /* cache of as_id; only valid if npages != 0 */

Thanks,
Sean Christopherson July 7, 2020, 6:17 a.m. UTC | #3
On Fri, Jul 03, 2020 at 02:41:22PM -0400, Peter Xu wrote:
> On Thu, Jul 02, 2020 at 04:08:49PM -0700, Sean Christopherson wrote:
> > On Mon, Jun 01, 2020 at 07:59:45AM -0400, Peter Xu wrote:
> > > Cache the address space ID just like the slot ID.  It will be used in
> > > order to fill in the dirty ring entries.
> > > 
> > > Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> > > Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > > Signed-off-by: Peter Xu <peterx@redhat.com>
> > > ---
> > >  include/linux/kvm_host.h | 1 +
> > >  virt/kvm/kvm_main.c      | 1 +
> > >  2 files changed, 2 insertions(+)
> > > 
> > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > > index 01276e3d01b9..5e7bbaf7a36b 100644
> > > --- a/include/linux/kvm_host.h
> > > +++ b/include/linux/kvm_host.h
> > > @@ -346,6 +346,7 @@ struct kvm_memory_slot {
> > >  	unsigned long userspace_addr;
> > >  	u32 flags;
> > >  	short id;
> > > +	u16 as_id;
> > >  };
> > >  
> > >  static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memslot)
> > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > > index 74bdb7bf3295..ebdd98a30e82 100644
> > > --- a/virt/kvm/kvm_main.c
> > > +++ b/virt/kvm/kvm_main.c
> > > @@ -1243,6 +1243,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
> > >  	if (!mem->memory_size)
> > >  		return kvm_delete_memslot(kvm, mem, &old, as_id);
> > 
> > This technically needs to set as_id in the deleted memslot.  I highly doubt
> > it will ever matter from a functionality perspective, but it'd be confusing
> > to encounter a memslot whose as_id did not match that of its owner.
> 
> Yeah it shouldn't matter because as_id is directly passed in to look up the
> pointer of kvm_memslots in kvm_delete_memslot, and memslot->as_id shouldn't be
> further referenced.
> 
> I can add a comment above if this can clarify things a bit:
> 
> +	u16 as_id; /* cache of as_id; only valid if npages != 0 */

Why not just set it?  It's a single line of code, and there's more than one
"shouldn't" in the above.

Patch
diff mbox series

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 01276e3d01b9..5e7bbaf7a36b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -346,6 +346,7 @@  struct kvm_memory_slot {
 	unsigned long userspace_addr;
 	u32 flags;
 	short id;
+	u16 as_id;
 };
 
 static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memslot)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 74bdb7bf3295..ebdd98a30e82 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1243,6 +1243,7 @@  int __kvm_set_memory_region(struct kvm *kvm,
 	if (!mem->memory_size)
 		return kvm_delete_memslot(kvm, mem, &old, as_id);
 
+	new.as_id = as_id;
 	new.id = id;
 	new.base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
 	new.npages = mem->memory_size >> PAGE_SHIFT;