Re: [v4 1/5] KVM: PPC: Book3S HV: Disable page merging in H_SVM_INIT_START
On Fri, Jul 17, 2020 at 01:00:23AM -0700, Ram Pai wrote:
> Page-merging of pages in memory-slots associated with a Secure VM,
> is disabled in H_SVM_PAGE_IN handler.
>
> This operation should have been done much earlier; the moment the VM
> is initiated for secure-transition. Delaying this operation, increases
> the probability for those pages to acquire new references , making it
> impossible to migrate those pages.
>
> Disable page-migration in H_SVM_INIT_START handling.
>
> Signed-off-by: Ram Pai
Reviewed-by: Bharata B Rao
with a few observations below...
> ---
> Documentation/powerpc/ultravisor.rst | 1 +
> arch/powerpc/kvm/book3s_hv_uvmem.c | 98
> +++-
> 2 files changed, 76 insertions(+), 23 deletions(-)
>
> diff --git a/Documentation/powerpc/ultravisor.rst
> b/Documentation/powerpc/ultravisor.rst
> index df136c8..a1c8c37 100644
> --- a/Documentation/powerpc/ultravisor.rst
> +++ b/Documentation/powerpc/ultravisor.rst
> @@ -895,6 +895,7 @@ Return values
> One of the following values:
>
> * H_SUCCESS on success.
> +* H_STATEif the VM is not in a position to switch to secure.
>
> Description
> ~~~
> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c
> b/arch/powerpc/kvm/book3s_hv_uvmem.c
> index e6f76bc..0baa293 100644
> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
> @@ -211,6 +211,65 @@ static bool kvmppc_gfn_is_uvmem_pfn(unsigned long gfn,
> struct kvm *kvm,
> return false;
> }
>
> +static int kvmppc_memslot_page_merge(struct kvm *kvm,
> + struct kvm_memory_slot *memslot, bool merge)
> +{
> + unsigned long gfn = memslot->base_gfn;
> + unsigned long end, start = gfn_to_hva(kvm, gfn);
> + int ret = 0;
> + struct vm_area_struct *vma;
> + int merge_flag = (merge) ? MADV_MERGEABLE : MADV_UNMERGEABLE;
> +
> + if (kvm_is_error_hva(start))
> + return H_STATE;
> +
> + end = start + (memslot->npages << PAGE_SHIFT);
> +
> + mmap_write_lock(kvm->mm);
> + do {
> + vma = find_vma_intersection(kvm->mm, start, end);
> + if (!vma) {
> + ret = H_STATE;
> + break;
> + }
> + ret = ksm_madvise(vma, vma->vm_start, vma->vm_end,
> + merge_flag, &vma->vm_flags);
> + if (ret) {
> + ret = H_STATE;
> + break;
> + }
> + start = vma->vm_end + 1;
This should be start = vma->vm_end I believe.
> + } while (end > vma->vm_end);
> +
> + mmap_write_unlock(kvm->mm);
> + return ret;
> +}
> +
> +static int __kvmppc_page_merge(struct kvm *kvm, bool merge)
> +{
> + struct kvm_memslots *slots;
> + struct kvm_memory_slot *memslot;
> + int ret = 0;
> +
> + slots = kvm_memslots(kvm);
> + kvm_for_each_memslot(memslot, slots) {
> + ret = kvmppc_memslot_page_merge(kvm, memslot, merge);
> + if (ret)
> + break;
> + }
> + return ret;
> +}
You walk through all the slots here to issue kvm_madvise, but...
> +
> +static inline int kvmppc_disable_page_merge(struct kvm *kvm)
> +{
> + return __kvmppc_page_merge(kvm, false);
> +}
> +
> +static inline int kvmppc_enable_page_merge(struct kvm *kvm)
> +{
> + return __kvmppc_page_merge(kvm, true);
> +}
> +
> unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
> {
> struct kvm_memslots *slots;
> @@ -232,11 +291,18 @@ unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
> return H_AUTHORITY;
>
> srcu_idx = srcu_read_lock(&kvm->srcu);
> +
> + /* disable page-merging for all memslot */
> + ret = kvmppc_disable_page_merge(kvm);
> + if (ret)
> + goto out;
> +
> + /* register the memslot */
> slots = kvm_memslots(kvm);
> kvm_for_each_memslot(memslot, slots) {
... you are walking thro' the same set of slots here anyway. I think
it makes sense to issue merge advices from here itself. That will
help you to share code with kvmppc_memslot_create() in 5/5.
All the below 3 calls are common to both the code paths, I think
they can be carved out into a separate function if you prefer.
kvmppc_uvmem_slot_init
kvmppc_memslot_page_merge
uv_register_mem_slot
Regards,
Bharata.
[v4 1/5] KVM: PPC: Book3S HV: Disable page merging in H_SVM_INIT_START
Page-merging of pages in memory-slots associated with a Secure VM,
is disabled in H_SVM_PAGE_IN handler.
This operation should have been done much earlier; the moment the VM
is initiated for secure-transition. Delaying this operation, increases
the probability for those pages to acquire new references , making it
impossible to migrate those pages.
Disable page-migration in H_SVM_INIT_START handling.
Signed-off-by: Ram Pai
---
Documentation/powerpc/ultravisor.rst | 1 +
arch/powerpc/kvm/book3s_hv_uvmem.c | 98 +++-
2 files changed, 76 insertions(+), 23 deletions(-)
diff --git a/Documentation/powerpc/ultravisor.rst
b/Documentation/powerpc/ultravisor.rst
index df136c8..a1c8c37 100644
--- a/Documentation/powerpc/ultravisor.rst
+++ b/Documentation/powerpc/ultravisor.rst
@@ -895,6 +895,7 @@ Return values
One of the following values:
* H_SUCCESS on success.
+* H_STATEif the VM is not in a position to switch to secure.
Description
~~~
diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c
b/arch/powerpc/kvm/book3s_hv_uvmem.c
index e6f76bc..0baa293 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -211,6 +211,65 @@ static bool kvmppc_gfn_is_uvmem_pfn(unsigned long gfn,
struct kvm *kvm,
return false;
}
+static int kvmppc_memslot_page_merge(struct kvm *kvm,
+ struct kvm_memory_slot *memslot, bool merge)
+{
+ unsigned long gfn = memslot->base_gfn;
+ unsigned long end, start = gfn_to_hva(kvm, gfn);
+ int ret = 0;
+ struct vm_area_struct *vma;
+ int merge_flag = (merge) ? MADV_MERGEABLE : MADV_UNMERGEABLE;
+
+ if (kvm_is_error_hva(start))
+ return H_STATE;
+
+ end = start + (memslot->npages << PAGE_SHIFT);
+
+ mmap_write_lock(kvm->mm);
+ do {
+ vma = find_vma_intersection(kvm->mm, start, end);
+ if (!vma) {
+ ret = H_STATE;
+ break;
+ }
+ ret = ksm_madvise(vma, vma->vm_start, vma->vm_end,
+ merge_flag, &vma->vm_flags);
+ if (ret) {
+ ret = H_STATE;
+ break;
+ }
+ start = vma->vm_end + 1;
+ } while (end > vma->vm_end);
+
+ mmap_write_unlock(kvm->mm);
+ return ret;
+}
+
+static int __kvmppc_page_merge(struct kvm *kvm, bool merge)
+{
+ struct kvm_memslots *slots;
+ struct kvm_memory_slot *memslot;
+ int ret = 0;
+
+ slots = kvm_memslots(kvm);
+ kvm_for_each_memslot(memslot, slots) {
+ ret = kvmppc_memslot_page_merge(kvm, memslot, merge);
+ if (ret)
+ break;
+ }
+ return ret;
+}
+
+static inline int kvmppc_disable_page_merge(struct kvm *kvm)
+{
+ return __kvmppc_page_merge(kvm, false);
+}
+
+static inline int kvmppc_enable_page_merge(struct kvm *kvm)
+{
+ return __kvmppc_page_merge(kvm, true);
+}
+
unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
{
struct kvm_memslots *slots;
@@ -232,11 +291,18 @@ unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
return H_AUTHORITY;
srcu_idx = srcu_read_lock(&kvm->srcu);
+
+ /* disable page-merging for all memslot */
+ ret = kvmppc_disable_page_merge(kvm);
+ if (ret)
+ goto out;
+
+ /* register the memslot */
slots = kvm_memslots(kvm);
kvm_for_each_memslot(memslot, slots) {
if (kvmppc_uvmem_slot_init(kvm, memslot)) {
ret = H_PARAMETER;
- goto out;
+ break;
}
ret = uv_register_mem_slot(kvm->arch.lpid,
memslot->base_gfn << PAGE_SHIFT,
@@ -245,9 +311,12 @@ unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
if (ret < 0) {
kvmppc_uvmem_slot_free(kvm, memslot);
ret = H_PARAMETER;
- goto out;
+ break;
}
}
+
+ if (ret)
+ kvmppc_enable_page_merge(kvm);
out:
srcu_read_unlock(&kvm->srcu, srcu_idx);
return ret;
@@ -384,7 +453,7 @@ static struct page *kvmppc_uvmem_get_page(unsigned long
gpa, struct kvm *kvm)
*/
static int kvmppc_svm_page_in(struct vm_area_struct *vma, unsigned long start,
unsigned long end, unsigned long gpa, struct kvm *kvm,
- unsigned long page_shift, bool *downgrade)
+ unsigned long page_shift)
{
unsigned long src_pfn, dst_pfn = 0;
struct migrate_vma mig;
@@ -400,18 +469,6 @@ static int kvmppc_svm_page_in(struct vm_area_struct *vma,
unsigned long start,
mig.src = &src_pfn;
mig.dst = &dst_pfn;
- /*
-* We come here
