The page requested for page-in; sometimes, can have transient
references, and hence cannot migrate immediately. Retry a few times
before returning error.
The same is true for non-migrated pages that are migrated in
H_SVM_INIT_DONE hanlder. Retry a few times before returning error.
H_SVM_PAGE_IN interface is enhanced to return H_BUSY if the page is
not in a migratable state.
Cc: Paul Mackerras <pau...@ozlabs.org>
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Bharata B Rao <bhar...@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
Cc: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com>
Cc: Laurent Dufour <lduf...@linux.ibm.com>
Cc: Thiago Jung Bauermann <bauer...@linux.ibm.com>
Cc: David Gibson <da...@gibson.dropbear.id.au>
Cc: Claudio Carvalho <cclau...@linux.ibm.com>
Cc: kvm-...@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Ram Pai <linux...@us.ibm.com>
---
Documentation/powerpc/ultravisor.rst | 1 +
arch/powerpc/kvm/book3s_hv_uvmem.c | 106 ++++++++++++++++++++++++-----------
2 files changed, 74 insertions(+), 33 deletions(-)
diff --git a/Documentation/powerpc/ultravisor.rst
b/Documentation/powerpc/ultravisor.rst
index ba6b1bf..fe533ad 100644
--- a/Documentation/powerpc/ultravisor.rst
+++ b/Documentation/powerpc/ultravisor.rst
@@ -1035,6 +1035,7 @@ Return values
* H_PARAMETER if ``guest_pa`` is invalid.
* H_P2 if ``flags`` is invalid.
* H_P3 if ``order`` of page is invalid.
+ * H_BUSY if ``page`` is not in a state to pagein
Description
~~~~~~~~~~~
diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c
b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 3274663..a206984 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -672,7 +672,7 @@ static int kvmppc_svm_migrate_page(struct vm_area_struct
*vma,
return ret;
if (!(*mig.src & MIGRATE_PFN_MIGRATE)) {
- ret = -1;
+ ret = -2;
goto out_finalize;
}
@@ -700,43 +700,73 @@ static int kvmppc_svm_migrate_page(struct vm_area_struct
*vma,
return ret;
}
-int kvmppc_uv_migrate_mem_slot(struct kvm *kvm,
- const struct kvm_memory_slot *memslot)
+/*
+ * return 1, if some page migration failed because of transient error,
+ * while the remaining pages migrated successfully.
+ * The caller can use this as a hint to retry.
+ *
+ * return 0 otherwise. *ret indicates the success status
+ * of this call.
+ */
+static bool __kvmppc_uv_migrate_mem_slot(struct kvm *kvm,
+ const struct kvm_memory_slot *memslot, int *ret)
{
unsigned long gfn = memslot->base_gfn;
struct vm_area_struct *vma;
unsigned long start, end;
- int ret = 0;
+ bool retry = false;
+ *ret = 0;
while (kvmppc_next_nontransitioned_gfn(memslot, kvm, &gfn)) {
mmap_read_lock(kvm->mm);
start = gfn_to_hva(kvm, gfn);
if (kvm_is_error_hva(start)) {
- ret = H_STATE;
+ *ret = H_STATE;
goto next;
}
end = start + (1UL << PAGE_SHIFT);
vma = find_vma_intersection(kvm->mm, start, end);
if (!vma || vma->vm_start > start || vma->vm_end < end) {
- ret = H_STATE;
+ *ret = H_STATE;
goto next;
}
mutex_lock(&kvm->arch.uvmem_lock);
- ret = kvmppc_svm_migrate_page(vma, start, end,
+ *ret = kvmppc_svm_migrate_page(vma, start, end,
(gfn << PAGE_SHIFT), kvm, PAGE_SHIFT, false);
mutex_unlock(&kvm->arch.uvmem_lock);
- if (ret)
- ret = H_STATE;
next:
mmap_read_unlock(kvm->mm);
+ if (*ret == -2) {
+ retry = true;
+ continue;
+ }
- if (ret)
- break;
+ if (*ret)
+ return false;
}
+ return retry;
+}
+
+#define REPEAT_COUNT 10
+
+int kvmppc_uv_migrate_mem_slot(struct kvm *kvm,
+ const struct kvm_memory_slot *memslot)
+{
+ int ret = 0, repeat_count = REPEAT_COUNT;
+
+ /*
+ * try migration of pages in the memslot 'repeat_count' number of
+ * times, provided each time migration fails because of transient
+ * errors only.
+ */
+ while (__kvmppc_uv_migrate_mem_slot(kvm, memslot, &ret) &&
+ repeat_count--)
+ ;
+
return ret;
}
@@ -812,7 +842,7 @@ unsigned long kvmppc_h_svm_page_in(struct kvm *kvm,
unsigned long gpa,
struct vm_area_struct *vma;
int srcu_idx;
unsigned long gfn = gpa >> page_shift;
- int ret;
+ int ret, repeat_count = REPEAT_COUNT;
if (!(kvm->arch.secure_guest & KVMPPC_SECURE_INIT_START))
return H_UNSUPPORTED;
@@ -826,34 +856,44 @@ unsigned long kvmppc_h_svm_page_in(struct kvm *kvm,
unsigned long gpa,
if (flags & H_PAGE_IN_SHARED)
return kvmppc_share_page(kvm, gpa, page_shift);
- ret = H_PARAMETER;
srcu_idx = srcu_read_lock(&kvm->srcu);
- mmap_read_lock(kvm->mm);
- start = gfn_to_hva(kvm, gfn);
- if (kvm_is_error_hva(start))
- goto out;
-
- mutex_lock(&kvm->arch.uvmem_lock);
/* Fail the page-in request of an already paged-in page */
- if (kvmppc_gfn_is_uvmem_pfn(gfn, kvm, NULL))
- goto out_unlock;
+ mutex_lock(&kvm->arch.uvmem_lock);
+ ret = kvmppc_gfn_is_uvmem_pfn(gfn, kvm, NULL);
+ mutex_unlock(&kvm->arch.uvmem_lock);
+ if (ret) {
+ srcu_read_unlock(&kvm->srcu, srcu_idx);
+ return H_PARAMETER;
+ }
- end = start + (1UL << page_shift);
- vma = find_vma_intersection(kvm->mm, start, end);
- if (!vma || vma->vm_start > start || vma->vm_end < end)
- goto out_unlock;
+ do {
+ ret = H_PARAMETER;
+ mmap_read_lock(kvm->mm);
- if (kvmppc_svm_migrate_page(vma, start, end, gpa, kvm, page_shift,
- true))
- goto out_unlock;
+ start = gfn_to_hva(kvm, gfn);
+ if (kvm_is_error_hva(start)) {
+ mmap_read_unlock(kvm->mm);
+ break;
+ }
- ret = H_SUCCESS;
+ end = start + (1UL << page_shift);
+ vma = find_vma_intersection(kvm->mm, start, end);
+ if (!vma || vma->vm_start > start || vma->vm_end < end) {
+ mmap_read_unlock(kvm->mm);
+ break;
+ }
+
+ mutex_lock(&kvm->arch.uvmem_lock);
+ ret = kvmppc_svm_migrate_page(vma, start, end, gpa, kvm,
page_shift, true);
+ mutex_unlock(&kvm->arch.uvmem_lock);
+
+ mmap_read_unlock(kvm->mm);
+ } while (ret == -2 && repeat_count--);
+
+ if (ret == -2)
+ ret = H_BUSY;
-out_unlock:
- mutex_unlock(&kvm->arch.uvmem_lock);
-out:
- mmap_read_unlock(kvm->mm);
srcu_read_unlock(&kvm->srcu, srcu_idx);
return ret;
}
--
1.8.3.1
