[v3 4/5] KVM: PPC: Book3S HV: retry page migration before erroring-out H_SVM_PAGE_IN
From: Ram Pai <hidden>
Date: 2020-07-11 09:24:58
Subsystem:
documentation, kernel virtual machine for powerpc (kvm/powerpc), linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Jonathan Corbet, Madhavan Srinivasan, Linus Torvalds
The page requested for page-in; sometimes, can have transient references, and hence cannot migrate immediately. 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 <redacted> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Bharata B Rao <redacted> Cc: Aneesh Kumar K.V <redacted> Cc: Sukadev Bhattiprolu <redacted> Cc: Laurent Dufour <redacted> Cc: Thiago Jung Bauermann <redacted> Cc: David Gibson <redacted> Cc: Claudio Carvalho <redacted> Cc: kvm-ppc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Signed-off-by: Ram Pai <redacted> --- Documentation/powerpc/ultravisor.rst | 1 + arch/powerpc/kvm/book3s_hv_uvmem.c | 54 +++++++++++++++++++++--------------- 2 files changed, 33 insertions(+), 22 deletions(-)
diff --git a/Documentation/powerpc/ultravisor.rst b/Documentation/powerpc/ultravisor.rst
index d98fc85..638d1a7 100644
--- a/Documentation/powerpc/ultravisor.rst
+++ b/Documentation/powerpc/ultravisor.rst@@ -1034,6 +1034,7 @@ 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 12ed52a..c9bdef6 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c@@ -843,7 +843,7 @@ 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;
@@ -857,34 +857,44 @@ 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); - down_write(&kvm->mm->mmap_sem); - 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; + down_write(&kvm->mm->mmap_sem); - 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)) { + up_write(&kvm->mm->mmap_sem); + 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) { + up_write(&kvm->mm->mmap_sem); + 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); + + up_write(&kvm->mm->mmap_sem); + } while (ret == -2 && repeat_count--); + + if (ret == -2) + ret = H_BUSY; -out_unlock: - mutex_unlock(&kvm->arch.uvmem_lock); -out: - up_write(&kvm->mm->mmap_sem); srcu_read_unlock(&kvm->srcu, srcu_idx); return ret; }
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1.8.3.1