| Message ID | 1594458827-31866-5-git-send-email-linuxram@us.ibm.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Migrate non-migrated pages of a SVM. | expand |
On Sat, Jul 11, 2020 at 02:13:46AM -0700, Ram Pai wrote: > The page requested for page-in; sometimes, can have transient > references, and hence cannot migrate immediately. Retry a few times > before returning error. As I noted in the previous patch, we need to understand what are these transient errors and they occur on what type of pages? The previous patch also introduced a bit of retry logic in the page-in path. Can you consolidate the retry logic into a separate patch? > > H_SVM_PAGE_IN interface is enhanced to return H_BUSY if the page is > not in a migratable state. > > Cc: Paul Mackerras <paulus@ozlabs.org> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Bharata B Rao <bharata@linux.ibm.com> > Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> > Cc: Laurent Dufour <ldufour@linux.ibm.com> > Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com> > Cc: David Gibson <david@gibson.dropbear.id.au> > Cc: Claudio Carvalho <cclaudio@linux.ibm.com> > Cc: kvm-ppc@vger.kernel.org > Cc: linuxppc-dev@lists.ozlabs.org > > Signed-off-by: Ram Pai <linuxram@us.ibm.com> > --- > 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); Again with ksm_madvise() moved to init time, check if you still need write mmap_sem here. Regards, Bharata.
On Mon, Jul 13, 2020 at 03:20:43PM +0530, Bharata B Rao wrote: > On Sat, Jul 11, 2020 at 02:13:46AM -0700, Ram Pai wrote: > > The page requested for page-in; sometimes, can have transient > > references, and hence cannot migrate immediately. Retry a few times > > before returning error. > > As I noted in the previous patch, we need to understand what are these > transient errors and they occur on what type of pages? Its not clear when they occur. But they occur quite irregularly and they do occur on pages that were shared in the previous boot. > > The previous patch also introduced a bit of retry logic in the > page-in path. Can you consolidate the retry logic into a separate > patch? yes. having the retry logic in a seperate patch gives us the flexibility to drop it, if needed. The retry patch is not the core element of this patch series. RP
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; }
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 <paulus@ozlabs.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Bharata B Rao <bharata@linux.ibm.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> Cc: Laurent Dufour <ldufour@linux.ibm.com> Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com> Cc: David Gibson <david@gibson.dropbear.id.au> Cc: Claudio Carvalho <cclaudio@linux.ibm.com> Cc: kvm-ppc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Signed-off-by: Ram Pai <linuxram@us.ibm.com> --- Documentation/powerpc/ultravisor.rst | 1 + arch/powerpc/kvm/book3s_hv_uvmem.c | 54 +++++++++++++++++++++--------------- 2 files changed, 33 insertions(+), 22 deletions(-)