* [PATCH v2 1/2] KVM: PPC: Book3S HV: move kvmppc_svm_page_out up
2020-07-27 19:24 [PATCH v2 0/2] Rework secure memslot dropping Ram Pai
@ 2020-07-27 19:24 ` Ram Pai
2020-07-27 19:24 ` [PATCH v2 2/2] KVM: PPC: Book3S HV: rework secure mem slot dropping Ram Pai
2020-07-28 5:52 ` [PATCH v2 0/2] Rework secure memslot dropping Paul Mackerras
2 siblings, 0 replies; 6+ messages in thread
From: Ram Pai @ 2020-07-27 19:24 UTC (permalink / raw)
To: kvm-ppc, linuxppc-dev
Cc: ldufour, linuxram, cclaudio, bharata, sathnaga, aneesh.kumar,
sukadev, bauerman, david
From: Laurent Dufour <ldufour@linux.ibm.com>
kvmppc_svm_page_out() will need to be called by kvmppc_uvmem_drop_pages()
so move it upper in this file.
Furthermore it will be interesting to call this function when already
holding the kvm->arch.uvmem_lock, so prefix the original function with __
and remove the locking in it, and introduce a wrapper which call that
function with the lock held.
There is no functional change.
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Bharata B Rao <bharata@linux.ibm.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
---
arch/powerpc/kvm/book3s_hv_uvmem.c | 166 ++++++++++++++++++++-----------------
1 file changed, 90 insertions(+), 76 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 5b917ea..565f24b 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -497,6 +497,96 @@ unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
}
/*
+ * Provision a new page on HV side and copy over the contents
+ * from secure memory using UV_PAGE_OUT uvcall.
+ * Caller must held kvm->arch.uvmem_lock.
+ */
+static int __kvmppc_svm_page_out(struct vm_area_struct *vma,
+ unsigned long start,
+ unsigned long end, unsigned long page_shift,
+ struct kvm *kvm, unsigned long gpa)
+{
+ unsigned long src_pfn, dst_pfn = 0;
+ struct migrate_vma mig;
+ struct page *dpage, *spage;
+ struct kvmppc_uvmem_page_pvt *pvt;
+ unsigned long pfn;
+ int ret = U_SUCCESS;
+
+ memset(&mig, 0, sizeof(mig));
+ mig.vma = vma;
+ mig.start = start;
+ mig.end = end;
+ mig.src = &src_pfn;
+ mig.dst = &dst_pfn;
+ mig.src_owner = &kvmppc_uvmem_pgmap;
+
+ /* The requested page is already paged-out, nothing to do */
+ if (!kvmppc_gfn_is_uvmem_pfn(gpa >> page_shift, kvm, NULL))
+ return ret;
+
+ ret = migrate_vma_setup(&mig);
+ if (ret)
+ return -1;
+
+ spage = migrate_pfn_to_page(*mig.src);
+ if (!spage || !(*mig.src & MIGRATE_PFN_MIGRATE))
+ goto out_finalize;
+
+ if (!is_zone_device_page(spage))
+ goto out_finalize;
+
+ dpage = alloc_page_vma(GFP_HIGHUSER, vma, start);
+ if (!dpage) {
+ ret = -1;
+ goto out_finalize;
+ }
+
+ lock_page(dpage);
+ pvt = spage->zone_device_data;
+ pfn = page_to_pfn(dpage);
+
+ /*
+ * This function is used in two cases:
+ * - When HV touches a secure page, for which we do UV_PAGE_OUT
+ * - When a secure page is converted to shared page, we *get*
+ * the page to essentially unmap the device page. In this
+ * case we skip page-out.
+ */
+ if (!pvt->skip_page_out)
+ ret = uv_page_out(kvm->arch.lpid, pfn << page_shift,
+ gpa, 0, page_shift);
+
+ if (ret == U_SUCCESS)
+ *mig.dst = migrate_pfn(pfn) | MIGRATE_PFN_LOCKED;
+ else {
+ unlock_page(dpage);
+ __free_page(dpage);
+ goto out_finalize;
+ }
+
+ migrate_vma_pages(&mig);
+
+out_finalize:
+ migrate_vma_finalize(&mig);
+ return ret;
+}
+
+static inline int kvmppc_svm_page_out(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ unsigned long page_shift,
+ struct kvm *kvm, unsigned long gpa)
+{
+ int ret;
+
+ mutex_lock(&kvm->arch.uvmem_lock);
+ ret = __kvmppc_svm_page_out(vma, start, end, page_shift, kvm, gpa);
+ mutex_unlock(&kvm->arch.uvmem_lock);
+
+ return ret;
+}
+
+/*
* Drop device pages that we maintain for the secure guest
*
* We first mark the pages to be skipped from UV_PAGE_OUT when there
@@ -866,82 +956,6 @@ unsigned long kvmppc_h_svm_page_in(struct kvm *kvm, unsigned long gpa,
return ret;
}
-/*
- * Provision a new page on HV side and copy over the contents
- * from secure memory using UV_PAGE_OUT uvcall.
- */
-static int kvmppc_svm_page_out(struct vm_area_struct *vma,
- unsigned long start,
- unsigned long end, unsigned long page_shift,
- struct kvm *kvm, unsigned long gpa)
-{
- unsigned long src_pfn, dst_pfn = 0;
- struct migrate_vma mig;
- struct page *dpage, *spage;
- struct kvmppc_uvmem_page_pvt *pvt;
- unsigned long pfn;
- int ret = U_SUCCESS;
-
- memset(&mig, 0, sizeof(mig));
- mig.vma = vma;
- mig.start = start;
- mig.end = end;
- mig.src = &src_pfn;
- mig.dst = &dst_pfn;
- mig.src_owner = &kvmppc_uvmem_pgmap;
-
- mutex_lock(&kvm->arch.uvmem_lock);
- /* The requested page is already paged-out, nothing to do */
- if (!kvmppc_gfn_is_uvmem_pfn(gpa >> page_shift, kvm, NULL))
- goto out;
-
- ret = migrate_vma_setup(&mig);
- if (ret)
- goto out;
-
- spage = migrate_pfn_to_page(*mig.src);
- if (!spage || !(*mig.src & MIGRATE_PFN_MIGRATE))
- goto out_finalize;
-
- if (!is_zone_device_page(spage))
- goto out_finalize;
-
- dpage = alloc_page_vma(GFP_HIGHUSER, vma, start);
- if (!dpage) {
- ret = -1;
- goto out_finalize;
- }
-
- lock_page(dpage);
- pvt = spage->zone_device_data;
- pfn = page_to_pfn(dpage);
-
- /*
- * This function is used in two cases:
- * - When HV touches a secure page, for which we do UV_PAGE_OUT
- * - When a secure page is converted to shared page, we *get*
- * the page to essentially unmap the device page. In this
- * case we skip page-out.
- */
- if (!pvt->skip_page_out)
- ret = uv_page_out(kvm->arch.lpid, pfn << page_shift,
- gpa, 0, page_shift);
-
- if (ret == U_SUCCESS)
- *mig.dst = migrate_pfn(pfn) | MIGRATE_PFN_LOCKED;
- else {
- unlock_page(dpage);
- __free_page(dpage);
- goto out_finalize;
- }
-
- migrate_vma_pages(&mig);
-out_finalize:
- migrate_vma_finalize(&mig);
-out:
- mutex_unlock(&kvm->arch.uvmem_lock);
- return ret;
-}
/*
* Fault handler callback that gets called when HV touches any page that
--
1.8.3.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v2 2/2] KVM: PPC: Book3S HV: rework secure mem slot dropping
2020-07-27 19:24 [PATCH v2 0/2] Rework secure memslot dropping Ram Pai
2020-07-27 19:24 ` [PATCH v2 1/2] KVM: PPC: Book3S HV: move kvmppc_svm_page_out up Ram Pai
@ 2020-07-27 19:24 ` Ram Pai
2020-07-28 5:52 ` [PATCH v2 0/2] Rework secure memslot dropping Paul Mackerras
2 siblings, 0 replies; 6+ messages in thread
From: Ram Pai @ 2020-07-27 19:24 UTC (permalink / raw)
To: kvm-ppc, linuxppc-dev
Cc: ldufour, linuxram, cclaudio, bharata, sathnaga, aneesh.kumar,
sukadev, bauerman, david
From: Laurent Dufour <ldufour@linux.ibm.com>
When a secure memslot is dropped, all the pages backed in the secure
device (aka really backed by secure memory by the Ultravisor)
should be paged out to a normal page. Previously, this was
achieved by triggering the page fault mechanism which is calling
kvmppc_svm_page_out() on each pages.
This can't work when hot unplugging a memory slot because the memory
slot is flagged as invalid and gfn_to_pfn() is then not trying to access
the page, so the page fault mechanism is not triggered.
Since the final goal is to make a call to kvmppc_svm_page_out() it seems
simpler to call directly instead of triggering such a mechanism. This
way kvmppc_uvmem_drop_pages() can be called even when hot unplugging a
memslot.
Since kvmppc_uvmem_drop_pages() is already holding kvm->arch.uvmem_lock,
the call to __kvmppc_svm_page_out() is made. As
__kvmppc_svm_page_out needs the vma pointer to migrate the pages,
the VMA is fetched in a lazy way, to not trigger find_vma() all
the time. In addition, the mmap_sem is held in read mode during
that time, not in write mode since the virual memory layout is not
impacted, and kvm->arch.uvmem_lock prevents concurrent operation
on the secure device.
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Bharata B Rao <bharata@linux.ibm.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
[modified the changelog description]
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
[modified check on the VMA in kvmppc_uvmem_drop_pages]
---
arch/powerpc/kvm/book3s_hv_uvmem.c | 52 +++++++++++++++++++++++++-------------
1 file changed, 35 insertions(+), 17 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 565f24b..0d49e34 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -594,35 +594,53 @@ static inline int kvmppc_svm_page_out(struct vm_area_struct *vma,
* fault on them, do fault time migration to replace the device PTEs in
* QEMU page table with normal PTEs from newly allocated pages.
*/
-void kvmppc_uvmem_drop_pages(const struct kvm_memory_slot *free,
+void kvmppc_uvmem_drop_pages(const struct kvm_memory_slot *slot,
struct kvm *kvm, bool skip_page_out)
{
int i;
struct kvmppc_uvmem_page_pvt *pvt;
- unsigned long pfn, uvmem_pfn;
- unsigned long gfn = free->base_gfn;
+ struct page *uvmem_page;
+ struct vm_area_struct *vma = NULL;
+ unsigned long uvmem_pfn, gfn;
+ unsigned long addr;
+
+ mmap_read_lock(kvm->mm);
+
+ addr = slot->userspace_addr;
- for (i = free->npages; i; --i, ++gfn) {
- struct page *uvmem_page;
+ gfn = slot->base_gfn;
+ for (i = slot->npages; i; --i, ++gfn, addr += PAGE_SIZE) {
+
+ /* Fetch the VMA if addr is not in the latest fetched one */
+ if (!vma || addr >= vma->vm_end) {
+ vma = find_vma_intersection(kvm->mm, addr, addr+1);
+ if (!vma) {
+ pr_err("Can't find VMA for gfn:0x%lx\n", gfn);
+ break;
+ }
+ }
mutex_lock(&kvm->arch.uvmem_lock);
- if (!kvmppc_gfn_is_uvmem_pfn(gfn, kvm, &uvmem_pfn)) {
+
+ if (kvmppc_gfn_is_uvmem_pfn(gfn, kvm, &uvmem_pfn)) {
+ uvmem_page = pfn_to_page(uvmem_pfn);
+ pvt = uvmem_page->zone_device_data;
+ pvt->skip_page_out = skip_page_out;
+ pvt->remove_gfn = true;
+
+ if (__kvmppc_svm_page_out(vma, addr, addr + PAGE_SIZE,
+ PAGE_SHIFT, kvm, pvt->gpa))
+ pr_err("Can't page out gpa:0x%lx addr:0x%lx\n",
+ pvt->gpa, addr);
+ } else {
+ /* Remove the shared flag if any */
kvmppc_gfn_remove(gfn, kvm);
- mutex_unlock(&kvm->arch.uvmem_lock);
- continue;
}
- uvmem_page = pfn_to_page(uvmem_pfn);
- pvt = uvmem_page->zone_device_data;
- pvt->skip_page_out = skip_page_out;
- pvt->remove_gfn = true;
mutex_unlock(&kvm->arch.uvmem_lock);
-
- pfn = gfn_to_pfn(kvm, gfn);
- if (is_error_noslot_pfn(pfn))
- continue;
- kvm_release_pfn_clean(pfn);
}
+
+ mmap_read_unlock(kvm->mm);
}
unsigned long kvmppc_h_svm_init_abort(struct kvm *kvm)
--
1.8.3.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2 0/2] Rework secure memslot dropping
2020-07-27 19:24 [PATCH v2 0/2] Rework secure memslot dropping Ram Pai
2020-07-27 19:24 ` [PATCH v2 1/2] KVM: PPC: Book3S HV: move kvmppc_svm_page_out up Ram Pai
2020-07-27 19:24 ` [PATCH v2 2/2] KVM: PPC: Book3S HV: rework secure mem slot dropping Ram Pai
@ 2020-07-28 5:52 ` Paul Mackerras
2 siblings, 0 replies; 6+ messages in thread
From: Paul Mackerras @ 2020-07-28 5:52 UTC (permalink / raw)
To: Ram Pai
Cc: ldufour, cclaudio, kvm-ppc, bharata, sathnaga, aneesh.kumar,
sukadev, linuxppc-dev, bauerman, david
On Mon, Jul 27, 2020 at 12:24:27PM -0700, Ram Pai wrote:
> From: Laurent Dufour <ldufour@linux.ibm.com>
>
> When doing memory hotplug on a secure VM, the secure pages are not well
> cleaned from the secure device when dropping the memslot. This silent
> error, is then preventing the SVM to reboot properly after the following
> sequence of commands are run in the Qemu monitor:
>
> device_add pc-dimm,id=dimm1,memdev=mem1
> device_del dimm1
> device_add pc-dimm,id=dimm1,memdev=mem1
>
> At reboot time, when the kernel is booting again and switching to the
> secure mode, the page_in is failing for the pages in the memslot because
> the cleanup was not done properly, because the memslot is flagged as
> invalid during the hot unplug and thus the page fault mechanism is not
> triggered.
>
> To prevent that during the memslot dropping, instead of belonging on the
> page fault mechanism to trigger the page out of the secured pages, it seems
> simpler to directly call the function doing the page out. This way the
> state of the memslot is not interfering on the page out process.
>
> This series applies on top of the Ram's one titled:
> "[v6 0/5] Migrate non-migrated pages of a SVM."
Thanks, series applied to my kvm-ppc-next branch and pull request sent.
Paul.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2 1/2] KVM: PPC: Book3S HV: move kvmppc_svm_page_out up
2020-07-21 10:42 Laurent Dufour
@ 2020-07-21 10:42 ` Laurent Dufour
2020-07-21 21:28 ` Ram Pai
0 siblings, 1 reply; 6+ messages in thread
From: Laurent Dufour @ 2020-07-21 10:42 UTC (permalink / raw)
To: linuxppc-dev, linux-kernel, kvm-ppc, mpe, paulus
Cc: sukadev, linuxram, bauerman, bharata
kvmppc_svm_page_out() will need to be called by kvmppc_uvmem_drop_pages()
so move it upper in this file.
Furthermore it will be interesting to call this function when already
holding the kvm->arch.uvmem_lock, so prefix the original function with __
and remove the locking in it, and introduce a wrapper which call that
function with the lock held.
There is no functional change.
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
---
arch/powerpc/kvm/book3s_hv_uvmem.c | 166 ++++++++++++++++-------------
1 file changed, 90 insertions(+), 76 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index a2b4d259f8b0..5a4b02d3f651 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -526,6 +526,96 @@ unsigned long kvmppc_h_svm_init_done(struct kvm *kvm)
return ret;
}
+/*
+ * Provision a new page on HV side and copy over the contents
+ * from secure memory using UV_PAGE_OUT uvcall.
+ * Caller must held kvm->arch.uvmem_lock.
+ */
+static int __kvmppc_svm_page_out(struct vm_area_struct *vma,
+ unsigned long start,
+ unsigned long end, unsigned long page_shift,
+ struct kvm *kvm, unsigned long gpa)
+{
+ unsigned long src_pfn, dst_pfn = 0;
+ struct migrate_vma mig;
+ struct page *dpage, *spage;
+ struct kvmppc_uvmem_page_pvt *pvt;
+ unsigned long pfn;
+ int ret = U_SUCCESS;
+
+ memset(&mig, 0, sizeof(mig));
+ mig.vma = vma;
+ mig.start = start;
+ mig.end = end;
+ mig.src = &src_pfn;
+ mig.dst = &dst_pfn;
+ mig.src_owner = &kvmppc_uvmem_pgmap;
+
+ /* The requested page is already paged-out, nothing to do */
+ if (!kvmppc_gfn_is_uvmem_pfn(gpa >> page_shift, kvm, NULL))
+ return ret;
+
+ ret = migrate_vma_setup(&mig);
+ if (ret)
+ return -1;
+
+ spage = migrate_pfn_to_page(*mig.src);
+ if (!spage || !(*mig.src & MIGRATE_PFN_MIGRATE))
+ goto out_finalize;
+
+ if (!is_zone_device_page(spage))
+ goto out_finalize;
+
+ dpage = alloc_page_vma(GFP_HIGHUSER, vma, start);
+ if (!dpage) {
+ ret = -1;
+ goto out_finalize;
+ }
+
+ lock_page(dpage);
+ pvt = spage->zone_device_data;
+ pfn = page_to_pfn(dpage);
+
+ /*
+ * This function is used in two cases:
+ * - When HV touches a secure page, for which we do UV_PAGE_OUT
+ * - When a secure page is converted to shared page, we *get*
+ * the page to essentially unmap the device page. In this
+ * case we skip page-out.
+ */
+ if (!pvt->skip_page_out)
+ ret = uv_page_out(kvm->arch.lpid, pfn << page_shift,
+ gpa, 0, page_shift);
+
+ if (ret == U_SUCCESS)
+ *mig.dst = migrate_pfn(pfn) | MIGRATE_PFN_LOCKED;
+ else {
+ unlock_page(dpage);
+ __free_page(dpage);
+ goto out_finalize;
+ }
+
+ migrate_vma_pages(&mig);
+
+out_finalize:
+ migrate_vma_finalize(&mig);
+ return ret;
+}
+
+static inline int kvmppc_svm_page_out(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ unsigned long page_shift,
+ struct kvm *kvm, unsigned long gpa)
+{
+ int ret;
+
+ mutex_lock(&kvm->arch.uvmem_lock);
+ ret = __kvmppc_svm_page_out(vma, start, end, page_shift, kvm, gpa);
+ mutex_unlock(&kvm->arch.uvmem_lock);
+
+ return ret;
+}
+
/*
* Drop device pages that we maintain for the secure guest
*
@@ -898,82 +988,6 @@ unsigned long kvmppc_h_svm_page_in(struct kvm *kvm, unsigned long gpa,
return ret;
}
-/*
- * Provision a new page on HV side and copy over the contents
- * from secure memory using UV_PAGE_OUT uvcall.
- */
-static int kvmppc_svm_page_out(struct vm_area_struct *vma,
- unsigned long start,
- unsigned long end, unsigned long page_shift,
- struct kvm *kvm, unsigned long gpa)
-{
- unsigned long src_pfn, dst_pfn = 0;
- struct migrate_vma mig;
- struct page *dpage, *spage;
- struct kvmppc_uvmem_page_pvt *pvt;
- unsigned long pfn;
- int ret = U_SUCCESS;
-
- memset(&mig, 0, sizeof(mig));
- mig.vma = vma;
- mig.start = start;
- mig.end = end;
- mig.src = &src_pfn;
- mig.dst = &dst_pfn;
- mig.src_owner = &kvmppc_uvmem_pgmap;
-
- mutex_lock(&kvm->arch.uvmem_lock);
- /* The requested page is already paged-out, nothing to do */
- if (!kvmppc_gfn_is_uvmem_pfn(gpa >> page_shift, kvm, NULL))
- goto out;
-
- ret = migrate_vma_setup(&mig);
- if (ret)
- goto out;
-
- spage = migrate_pfn_to_page(*mig.src);
- if (!spage || !(*mig.src & MIGRATE_PFN_MIGRATE))
- goto out_finalize;
-
- if (!is_zone_device_page(spage))
- goto out_finalize;
-
- dpage = alloc_page_vma(GFP_HIGHUSER, vma, start);
- if (!dpage) {
- ret = -1;
- goto out_finalize;
- }
-
- lock_page(dpage);
- pvt = spage->zone_device_data;
- pfn = page_to_pfn(dpage);
-
- /*
- * This function is used in two cases:
- * - When HV touches a secure page, for which we do UV_PAGE_OUT
- * - When a secure page is converted to shared page, we *get*
- * the page to essentially unmap the device page. In this
- * case we skip page-out.
- */
- if (!pvt->skip_page_out)
- ret = uv_page_out(kvm->arch.lpid, pfn << page_shift,
- gpa, 0, page_shift);
-
- if (ret == U_SUCCESS)
- *mig.dst = migrate_pfn(pfn) | MIGRATE_PFN_LOCKED;
- else {
- unlock_page(dpage);
- __free_page(dpage);
- goto out_finalize;
- }
-
- migrate_vma_pages(&mig);
-out_finalize:
- migrate_vma_finalize(&mig);
-out:
- mutex_unlock(&kvm->arch.uvmem_lock);
- return ret;
-}
/*
* Fault handler callback that gets called when HV touches any page that
--
2.27.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2 1/2] KVM: PPC: Book3S HV: move kvmppc_svm_page_out up
2020-07-21 10:42 ` [PATCH v2 1/2] KVM: PPC: Book3S HV: move kvmppc_svm_page_out up Laurent Dufour
@ 2020-07-21 21:28 ` Ram Pai
0 siblings, 0 replies; 6+ messages in thread
From: Ram Pai @ 2020-07-21 21:28 UTC (permalink / raw)
To: Laurent Dufour
Cc: linux-kernel, kvm-ppc, bharata, paulus, sukadev, linuxppc-dev, bauerman
On Tue, Jul 21, 2020 at 12:42:01PM +0200, Laurent Dufour wrote:
> kvmppc_svm_page_out() will need to be called by kvmppc_uvmem_drop_pages()
> so move it upper in this file.
>
> Furthermore it will be interesting to call this function when already
> holding the kvm->arch.uvmem_lock, so prefix the original function with __
> and remove the locking in it, and introduce a wrapper which call that
> function with the lock held.
>
> There is no functional change.
Reviewed-by: Ram Pai <linuxram@us.ibm.com>
>
> Cc: Ram Pai <linuxram@us.ibm.com>
> Cc: Bharata B Rao <bharata@linux.ibm.com>
> Cc: Paul Mackerras <paulus@ozlabs.org>
> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
> ---
RP
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