Re: [RFC PATCH 4/6] kvm: Move private memory slots to start of memslots array

[Alex Williamson]

On Wed, 2012-12-05 at 19:24 -0200, Marcelo Tosatti wrote:
> On Mon, Dec 03, 2012 at 04:39:30PM -0700, Alex Williamson wrote:
> > In order to make the memslots array grow on demand, move the private
> > slots to the lower indexes of the array.  The private slots are
> > assumed likely to be in use, so if we didn't do this we'd end up
> > allocating the full memslots array all the time.
> 
> You're changing private slot ids. Fail to see why is that relevant
> to on-demand growing.

This series takes a really simple approach and grows the array up to the
given slot->id.  If we have private slots at the end of the array then
we always allocate the whole thing.  I'm playing with a version now that
fixes this, but complexity becomes a much more significant factor.
Thanks,

Alex

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Re: [RFC PATCH 4/6] kvm: Move private memory slots to start of memslots array

[Marcelo Tosatti]

On Mon, Dec 03, 2012 at 04:39:30PM -0700, Alex Williamson wrote:
> In order to make the memslots array grow on demand, move the private
> slots to the lower indexes of the array.  The private slots are
> assumed likely to be in use, so if we didn't do this we'd end up
> allocating the full memslots array all the time.

You're changing private slot ids. Fail to see why is that relevant
to on-demand growing.

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[RFC PATCH 4/6] kvm: Move private memory slots to start of memslots array

[Alex Williamson]

In order to make the memslots array grow on demand, move the private
slots to the lower indexes of the array.  The private slots are
assumed likely to be in use, so if we didn't do this we'd end up
allocating the full memslots array all the time.

Signed-off-by: Alex Williamson 
---
 arch/ia64/kvm/kvm-ia64.c |4 ++--
 arch/powerpc/kvm/book3s_hv.c |2 +-
 arch/x86/include/asm/vmx.h   |6 +++---
 arch/x86/kvm/vmx.c   |2 +-
 arch/x86/kvm/x86.c   |2 +-
 virt/kvm/kvm_main.c  |   15 ++-
 6 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index f1a46bd..012e5dd 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -949,7 +949,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = -EFAULT;
if (copy_from_user(&kvm_mem, argp, sizeof kvm_mem))
goto out;
-   kvm_userspace_mem.slot = kvm_mem.slot;
+   kvm_userspace_mem.slot = kvm_mem.slot + KVM_PRIVATE_MEM_SLOTS;
kvm_userspace_mem.flags = kvm_mem.flags;
kvm_userspace_mem.guest_phys_addr =
kvm_mem.guest_phys_addr;
@@ -1831,7 +1831,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
mutex_lock(&kvm->slots_lock);
 
r = -EINVAL;
-   if (log->slot >= KVM_USER_MEM_SLOTS)
+   if (log->slot >= KVM_MEM_SLOTS_NUM)
goto out;
 
memslot = id_to_memslot(kvm->memslots, log->slot);
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 75ce80e..56067db 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1262,7 +1262,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct 
kvm_dirty_log *log)
mutex_lock(&kvm->slots_lock);
 
r = -EINVAL;
-   if (log->slot >= KVM_USER_MEM_SLOTS)
+   if (log->slot >= KVM_MEM_SLOTS_NUM)
goto out;
 
memslot = id_to_memslot(kvm->memslots, log->slot);
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 72932d2..97bcd7d 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -427,9 +427,9 @@ enum vmcs_field {
 
 #define AR_RESERVD_MASK 0xfffe0f00
 
-#define TSS_PRIVATE_MEMSLOT(KVM_USER_MEM_SLOTS + 0)
-#define APIC_ACCESS_PAGE_PRIVATE_MEMSLOT   (KVM_USER_MEM_SLOTS + 1)
-#define IDENTITY_PAGETABLE_PRIVATE_MEMSLOT (KVM_USER_MEM_SLOTS + 2)
+#define TSS_PRIVATE_MEMSLOT0
+#define APIC_ACCESS_PAGE_PRIVATE_MEMSLOT   1
+#define IDENTITY_PAGETABLE_PRIVATE_MEMSLOT 2
 
 #define VMX_NR_VPIDS   (1 << 16)
 #define VMX_VPID_EXTENT_SINGLE_CONTEXT 1
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f858159..2bb9157 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2750,7 +2750,7 @@ static gva_t rmode_tss_base(struct kvm *kvm)
gfn_t base_gfn;
 
slots = kvm_memslots(kvm);
-   slot = id_to_memslot(slots, 0);
+   slot = id_to_memslot(slots, KVM_PRIVATE_MEM_SLOTS);
base_gfn = slot->base_gfn + slot->npages - 3;
 
return base_gfn << PAGE_SHIFT;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1aa3fae..8765485 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6449,7 +6449,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
int map_flags = MAP_PRIVATE | MAP_ANONYMOUS;
 
/* Prevent internal slot pages from being moved by fork()/COW. */
-   if (memslot->id >= KVM_USER_MEM_SLOTS)
+   if (memslot->id < KVM_PRIVATE_MEM_SLOTS)
map_flags = MAP_SHARED | MAP_ANONYMOUS;
 
/*To keep backward compatibility with older userspace,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4f8ae4b..3ce2664 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -761,7 +761,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
/* Check for overlaps */
r = -EEXIST;
kvm_for_each_memslot(slot, kvm->memslots) {
-   if (slot->id >= KVM_USER_MEM_SLOTS || slot == memslot)
+   if (slot->id < KVM_PRIVATE_MEM_SLOTS || slot == memslot)
continue;
if (!((base_gfn + npages <= slot->base_gfn) ||
  (base_gfn >= slot->base_gfn + slot->npages)))
@@ -879,7 +879,7 @@ int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
   kvm_userspace_memory_region *mem,
   int user_alloc)
 {
-   if (mem->slot >= KVM_USER_MEM_SLOTS)
+   if (mem->slot >= KVM_MEM_SLOTS_NUM)
return -EINVAL;
return kvm_set_memory_region(kvm, mem, user_alloc);
 }
@@ -893,7 +893,7 @@ int kvm_get_dirty_log(struct kvm *kvm,
unsigned long any = 0;
 
r = -EINVAL;
-   if (log->slot >= KVM_USER_MEM_SLOT