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KVM: s390: move pv gmap functions into kvm

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Move gmap related functions from kernel/uv into kvm.

Create a new file to collect gmap-related functions.

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
[fixed unpack_one(), thanks mhartmay@linux.ibm.com]
Link: https://lore.kernel.org/r/20250123144627.312456-6-imbrenda@linux.ibm.com
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20250123144627.312456-6-imbrenda@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2025-01-23 15:46:17 +01:00
parent 63e7151989
commit 5cbe24350b
10 changed files with 315 additions and 268 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
arch/s390/include/asm/gmap.h
View file

@ -149,6 +149,7 @@ int s390_replace_asce(struct gmap *gmap);
void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns);
int __s390_uv_destroy_range(struct mm_struct *mm, unsigned long start,
unsigned long end, bool interruptible);
int kvm_s390_wiggle_split_folio(struct mm_struct *mm, struct folio *folio, bool split);
/**
* s390_uv_destroy_range - Destroy a range of pages in the given mm.

6
arch/s390/include/asm/uv.h
View file

@ -628,12 +628,12 @@ static inline int is_prot_virt_host(void)
}
int uv_pin_shared(unsigned long paddr);
int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb);
int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr);
int uv_destroy_folio(struct folio *folio);
int uv_destroy_pte(pte_t pte);
int uv_convert_from_secure_pte(pte_t pte);
int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr);
int make_folio_secure(struct folio *folio, struct uv_cb_header *uvcb);
int uv_convert_from_secure(unsigned long paddr);
int uv_convert_from_secure_folio(struct folio *folio);
void setup_uv(void);

292
arch/s390/kernel/uv.c
View file

@ -19,19 +19,6 @@
#include <asm/sections.h>
#include <asm/uv.h>
#if !IS_ENABLED(CONFIG_KVM)
unsigned long __gmap_translate(struct gmap *gmap, unsigned long gaddr)
{
return 0;
}
int gmap_fault(struct gmap *gmap, unsigned long gaddr,
unsigned int fault_flags)
{
return 0;
}
#endif
/* the bootdata_preserved fields come from ones in arch/s390/boot/uv.c */
int __bootdata_preserved(prot_virt_guest);
EXPORT_SYMBOL(prot_virt_guest);
@ -159,6 +146,7 @@ int uv_destroy_folio(struct folio *folio)
folio_put(folio);
return rc;
}
EXPORT_SYMBOL(uv_destroy_folio);
/*
* The present PTE still indirectly holds a folio reference through the mapping.
@ -175,7 +163,7 @@ int uv_destroy_pte(pte_t pte)
*
* @paddr: Absolute host address of page to be exported
*/
static int uv_convert_from_secure(unsigned long paddr)
int uv_convert_from_secure(unsigned long paddr)
{
struct uv_cb_cfs uvcb = {
.header.cmd = UVC_CMD_CONV_FROM_SEC_STOR,
@ -187,11 +175,12 @@ static int uv_convert_from_secure(unsigned long paddr)
return -EINVAL;
return 0;
}
EXPORT_SYMBOL_GPL(uv_convert_from_secure);
/*
* The caller must already hold a reference to the folio.
*/
static int uv_convert_from_secure_folio(struct folio *folio)
int uv_convert_from_secure_folio(struct folio *folio)
{
int rc;
@ -206,6 +195,7 @@ static int uv_convert_from_secure_folio(struct folio *folio)
folio_put(folio);
return rc;
}
EXPORT_SYMBOL_GPL(uv_convert_from_secure_folio);
/*
* The present PTE still indirectly holds a folio reference through the mapping.
@ -237,13 +227,33 @@ static int expected_folio_refs(struct folio *folio)
return res;
}
static int make_folio_secure(struct folio *folio, struct uv_cb_header *uvcb)
/**
* make_folio_secure() - make a folio secure
* @folio: the folio to make secure
* @uvcb: the uvcb that describes the UVC to be used
*
* The folio @folio will be made secure if possible, @uvcb will be passed
* as-is to the UVC.
*
* Return: 0 on success;
* -EBUSY if the folio is in writeback or has too many references;
* -E2BIG if the folio is large;
* -EAGAIN if the UVC needs to be attempted again;
* -ENXIO if the address is not mapped;
* -EINVAL if the UVC failed for other reasons.
*
* Context: The caller must hold exactly one extra reference on the folio
* (it's the same logic as split_folio())
*/
int make_folio_secure(struct folio *folio, struct uv_cb_header *uvcb)
{
int expected, cc = 0;
if (folio_test_large(folio))
return -E2BIG;
if (folio_test_writeback(folio))
return -EAGAIN;
expected = expected_folio_refs(folio);
return -EBUSY;
expected = expected_folio_refs(folio) + 1;
if (!folio_ref_freeze(folio, expected))
return -EBUSY;
set_bit(PG_arch_1, &folio->flags);
@ -267,251 +277,7 @@ static int make_folio_secure(struct folio *folio, struct uv_cb_header *uvcb)
return -EAGAIN;
return uvcb->rc == 0x10a ? -ENXIO : -EINVAL;
}
/**
* should_export_before_import - Determine whether an export is needed
* before an import-like operation
* @uvcb: the Ultravisor control block of the UVC to be performed
* @mm: the mm of the process
*
* Returns whether an export is needed before every import-like operation.
* This is needed for shared pages, which don't trigger a secure storage
* exception when accessed from a different guest.
*
* Although considered as one, the Unpin Page UVC is not an actual import,
* so it is not affected.
*
* No export is needed also when there is only one protected VM, because the
* page cannot belong to the wrong VM in that case (there is no "other VM"
* it can belong to).
*
* Return: true if an export is needed before every import, otherwise false.
*/
static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
{
/*
* The misc feature indicates, among other things, that importing a
* shared page from a different protected VM will automatically also
* transfer its ownership.
*/
if (uv_has_feature(BIT_UV_FEAT_MISC))
return false;
if (uvcb->cmd == UVC_CMD_UNPIN_PAGE_SHARED)
return false;
return atomic_read(&mm->context.protected_count) > 1;
}
/*
* Drain LRU caches: the local one on first invocation and the ones of all
* CPUs on successive invocations. Returns "true" on the first invocation.
*/
static bool drain_lru(bool *drain_lru_called)
{
/*
* If we have tried a local drain and the folio refcount
* still does not match our expected safe value, try with a
* system wide drain. This is needed if the pagevecs holding
* the page are on a different CPU.
*/
if (*drain_lru_called) {
lru_add_drain_all();
/* We give up here, don't retry immediately. */
return false;
}
/*
* We are here if the folio refcount does not match the
* expected safe value. The main culprits are usually
* pagevecs. With lru_add_drain() we drain the pagevecs
* on the local CPU so that hopefully the refcount will
* reach the expected safe value.
*/
lru_add_drain();
*drain_lru_called = true;
/* The caller should try again immediately */
return true;
}
/*
* Requests the Ultravisor to make a page accessible to a guest.
* If it's brought in the first time, it will be cleared. If
* it has been exported before, it will be decrypted and integrity
* checked.
*/
int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)
{
struct vm_area_struct *vma;
bool drain_lru_called = false;
spinlock_t *ptelock;
unsigned long uaddr;
struct folio *folio;
pte_t *ptep;
int rc;
again:
rc = -EFAULT;
mmap_read_lock(gmap->mm);
uaddr = __gmap_translate(gmap, gaddr);
if (IS_ERR_VALUE(uaddr))
goto out;
vma = vma_lookup(gmap->mm, uaddr);
if (!vma)
goto out;
/*
* Secure pages cannot be huge and userspace should not combine both.
* In case userspace does it anyway this will result in an -EFAULT for
* the unpack. The guest is thus never reaching secure mode. If
* userspace is playing dirty tricky with mapping huge pages later
* on this will result in a segmentation fault.
*/
if (is_vm_hugetlb_page(vma))
goto out;
rc = -ENXIO;
ptep = get_locked_pte(gmap->mm, uaddr, &ptelock);
if (!ptep)
goto out;
if (pte_present(*ptep) && !(pte_val(*ptep) & _PAGE_INVALID) && pte_write(*ptep)) {
folio = page_folio(pte_page(*ptep));
rc = -EAGAIN;
if (folio_test_large(folio)) {
rc = -E2BIG;
} else if (folio_trylock(folio)) {
if (should_export_before_import(uvcb, gmap->mm))
uv_convert_from_secure(PFN_PHYS(folio_pfn(folio)));
rc = make_folio_secure(folio, uvcb);
folio_unlock(folio);
}
/*
* Once we drop the PTL, the folio may get unmapped and
* freed immediately. We need a temporary reference.
*/
if (rc == -EAGAIN || rc == -E2BIG)
folio_get(folio);
}
pte_unmap_unlock(ptep, ptelock);
out:
mmap_read_unlock(gmap->mm);
switch (rc) {
case -E2BIG:
folio_lock(folio);
rc = split_folio(folio);
folio_unlock(folio);
folio_put(folio);
switch (rc) {
case 0:
/* Splitting succeeded, try again immediately. */
goto again;
case -EAGAIN:
/* Additional folio references. */
if (drain_lru(&drain_lru_called))
goto again;
return -EAGAIN;
case -EBUSY:
/* Unexpected race. */
return -EAGAIN;
}
WARN_ON_ONCE(1);
return -ENXIO;
case -EAGAIN:
/*
* If we are here because the UVC returned busy or partial
* completion, this is just a useless check, but it is safe.
*/
folio_wait_writeback(folio);
folio_put(folio);
return -EAGAIN;
case -EBUSY:
/* Additional folio references. */
if (drain_lru(&drain_lru_called))
goto again;
return -EAGAIN;
case -ENXIO:
if (gmap_fault(gmap, gaddr, FAULT_FLAG_WRITE))
return -EFAULT;
return -EAGAIN;
}
return rc;
}
EXPORT_SYMBOL_GPL(gmap_make_secure);
int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr)
{
struct uv_cb_cts uvcb = {
.header.cmd = UVC_CMD_CONV_TO_SEC_STOR,
.header.len = sizeof(uvcb),
.guest_handle = gmap->guest_handle,
.gaddr = gaddr,
};
return gmap_make_secure(gmap, gaddr, &uvcb);
}
EXPORT_SYMBOL_GPL(gmap_convert_to_secure);
/**
* gmap_destroy_page - Destroy a guest page.
* @gmap: the gmap of the guest
* @gaddr: the guest address to destroy
*
* An attempt will be made to destroy the given guest page. If the attempt
* fails, an attempt is made to export the page. If both attempts fail, an
* appropriate error is returned.
*/
int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
{
struct vm_area_struct *vma;
struct folio_walk fw;
unsigned long uaddr;
struct folio *folio;
int rc;
rc = -EFAULT;
mmap_read_lock(gmap->mm);
uaddr = __gmap_translate(gmap, gaddr);
if (IS_ERR_VALUE(uaddr))
goto out;
vma = vma_lookup(gmap->mm, uaddr);
if (!vma)
goto out;
/*
* Huge pages should not be able to become secure
*/
if (is_vm_hugetlb_page(vma))
goto out;
rc = 0;
folio = folio_walk_start(&fw, vma, uaddr, 0);
if (!folio)
goto out;
/*
* See gmap_make_secure(): large folios cannot be secure. Small
* folio implies FW_LEVEL_PTE.
*/
if (folio_test_large(folio) || !pte_write(fw.pte))
goto out_walk_end;
rc = uv_destroy_folio(folio);
/*
* Fault handlers can race; it is possible that two CPUs will fault
* on the same secure page. One CPU can destroy the page, reboot,
* re-enter secure mode and import it, while the second CPU was
* stuck at the beginning of the handler. At some point the second
* CPU will be able to progress, and it will not be able to destroy
* the page. In that case we do not want to terminate the process,
* we instead try to export the page.
*/
if (rc)
rc = uv_convert_from_secure_folio(folio);
out_walk_end:
folio_walk_end(&fw, vma);
out:
mmap_read_unlock(gmap->mm);
return rc;
}
EXPORT_SYMBOL_GPL(gmap_destroy_page);
EXPORT_SYMBOL_GPL(make_folio_secure);
/*
* To be called with the folio locked or with an extra reference! This will

2
arch/s390/kvm/Makefile
View file

@ -8,7 +8,7 @@ include $(srctree)/virt/kvm/Makefile.kvm
ccflags-y := -Ivirt/kvm -Iarch/s390/kvm
kvm-y += kvm-s390.o intercept.o interrupt.o priv.o sigp.o
kvm-y += diag.o gaccess.o guestdbg.o vsie.o pv.o
kvm-y += diag.o gaccess.o guestdbg.o vsie.o pv.o gmap.o
kvm-$(CONFIG_VFIO_PCI_ZDEV_KVM) += pci.o
obj-$(CONFIG_KVM) += kvm.o

212
arch/s390/kvm/gmap.c Normal file
View file

@ -0,0 +1,212 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Guest memory management for KVM/s390
*
* Copyright IBM Corp. 2008, 2020, 2024
*
* Author(s): Claudio Imbrenda <imbrenda@linux.ibm.com>
* Martin Schwidefsky <schwidefsky@de.ibm.com>
* David Hildenbrand <david@redhat.com>
* Janosch Frank <frankja@linux.vnet.ibm.com>
*/
#include <linux/compiler.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <linux/pgtable.h>
#include <linux/pagemap.h>
#include <asm/lowcore.h>
#include <asm/gmap.h>
#include <asm/uv.h>
#include "gmap.h"
/**
* should_export_before_import - Determine whether an export is needed
* before an import-like operation
* @uvcb: the Ultravisor control block of the UVC to be performed
* @mm: the mm of the process
*
* Returns whether an export is needed before every import-like operation.
* This is needed for shared pages, which don't trigger a secure storage
* exception when accessed from a different guest.
*
* Although considered as one, the Unpin Page UVC is not an actual import,
* so it is not affected.
*
* No export is needed also when there is only one protected VM, because the
* page cannot belong to the wrong VM in that case (there is no "other VM"
* it can belong to).
*
* Return: true if an export is needed before every import, otherwise false.
*/
static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
{
/*
* The misc feature indicates, among other things, that importing a
* shared page from a different protected VM will automatically also
* transfer its ownership.
*/
if (uv_has_feature(BIT_UV_FEAT_MISC))
return false;
if (uvcb->cmd == UVC_CMD_UNPIN_PAGE_SHARED)
return false;
return atomic_read(&mm->context.protected_count) > 1;
}
static int __gmap_make_secure(struct gmap *gmap, struct page *page, void *uvcb)
{
struct folio *folio = page_folio(page);
int rc;
/*
* Secure pages cannot be huge and userspace should not combine both.
* In case userspace does it anyway this will result in an -EFAULT for
* the unpack. The guest is thus never reaching secure mode.
* If userspace plays dirty tricks and decides to map huge pages at a
* later point in time, it will receive a segmentation fault or
* KVM_RUN will return -EFAULT.
*/
if (folio_test_hugetlb(folio))
return -EFAULT;
if (folio_test_large(folio)) {
mmap_read_unlock(gmap->mm);
rc = kvm_s390_wiggle_split_folio(gmap->mm, folio, true);
mmap_read_lock(gmap->mm);
if (rc)
return rc;
folio = page_folio(page);
}
if (!folio_trylock(folio))
return -EAGAIN;
if (should_export_before_import(uvcb, gmap->mm))
uv_convert_from_secure(folio_to_phys(folio));
rc = make_folio_secure(folio, uvcb);
folio_unlock(folio);
/*
* In theory a race is possible and the folio might have become
* large again before the folio_trylock() above. In that case, no
* action is performed and -EAGAIN is returned; the callers will
* have to try again later.
* In most cases this implies running the VM again, getting the same
* exception again, and make another attempt in this function.
* This is expected to happen extremely rarely.
*/
if (rc == -E2BIG)
return -EAGAIN;
/* The folio has too many references, try to shake some off */
if (rc == -EBUSY) {
mmap_read_unlock(gmap->mm);
kvm_s390_wiggle_split_folio(gmap->mm, folio, false);
mmap_read_lock(gmap->mm);
return -EAGAIN;
}
return rc;
}
/**
* gmap_make_secure() - make one guest page secure
* @gmap: the guest gmap
* @gaddr: the guest address that needs to be made secure
* @uvcb: the UVCB specifying which operation needs to be performed
*
* Context: needs to be called with kvm->srcu held.
* Return: 0 on success, < 0 in case of error (see __gmap_make_secure()).
*/
int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)
{
struct kvm *kvm = gmap->private;
struct page *page;
int rc = 0;
lockdep_assert_held(&kvm->srcu);
page = gfn_to_page(kvm, gpa_to_gfn(gaddr));
mmap_read_lock(gmap->mm);
if (page)
rc = __gmap_make_secure(gmap, page, uvcb);
kvm_release_page_clean(page);
mmap_read_unlock(gmap->mm);
return rc;
}
int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr)
{
struct uv_cb_cts uvcb = {
.header.cmd = UVC_CMD_CONV_TO_SEC_STOR,
.header.len = sizeof(uvcb),
.guest_handle = gmap->guest_handle,
.gaddr = gaddr,
};
return gmap_make_secure(gmap, gaddr, &uvcb);
}
/**
* __gmap_destroy_page() - Destroy a guest page.
* @gmap: the gmap of the guest
* @page: the page to destroy
*
* An attempt will be made to destroy the given guest page. If the attempt
* fails, an attempt is made to export the page. If both attempts fail, an
* appropriate error is returned.
*
* Context: must be called holding the mm lock for gmap->mm
*/
static int __gmap_destroy_page(struct gmap *gmap, struct page *page)
{
struct folio *folio = page_folio(page);
int rc;
/*
* See gmap_make_secure(): large folios cannot be secure. Small
* folio implies FW_LEVEL_PTE.
*/
if (folio_test_large(folio))
return -EFAULT;
rc = uv_destroy_folio(folio);
/*
* Fault handlers can race; it is possible that two CPUs will fault
* on the same secure page. One CPU can destroy the page, reboot,
* re-enter secure mode and import it, while the second CPU was
* stuck at the beginning of the handler. At some point the second
* CPU will be able to progress, and it will not be able to destroy
* the page. In that case we do not want to terminate the process,
* we instead try to export the page.
*/
if (rc)
rc = uv_convert_from_secure_folio(folio);
return rc;
}
/**
* gmap_destroy_page() - Destroy a guest page.
* @gmap: the gmap of the guest
* @gaddr: the guest address to destroy
*
* An attempt will be made to destroy the given guest page. If the attempt
* fails, an attempt is made to export the page. If both attempts fail, an
* appropriate error is returned.
*
* Context: may sleep.
*/
int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
{
struct page *page;
int rc = 0;
mmap_read_lock(gmap->mm);
page = gfn_to_page(gmap->private, gpa_to_gfn(gaddr));
if (page)
rc = __gmap_destroy_page(gmap, page);
kvm_release_page_clean(page);
mmap_read_unlock(gmap->mm);
return rc;
}

17
arch/s390/kvm/gmap.h Normal file
View file

@ -0,0 +1,17 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* KVM guest address space mapping code
*
* Copyright IBM Corp. 2007, 2016, 2025
* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
* Claudio Imbrenda <imbrenda@linux.ibm.com>
*/
#ifndef ARCH_KVM_S390_GMAP_H
#define ARCH_KVM_S390_GMAP_H
int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb);
int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr);
int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr);
#endif

3
arch/s390/kvm/intercept.c
View file

@ -21,6 +21,7 @@
#include "gaccess.h"
#include "trace.h"
#include "trace-s390.h"
#include "gmap.h"
u8 kvm_s390_get_ilen(struct kvm_vcpu *vcpu)
{
@ -549,7 +550,7 @@ static int handle_pv_uvc(struct kvm_vcpu *vcpu)
* If the unpin did not succeed, the guest will exit again for the UVC
* and we will retry the unpin.
*/
if (rc == -EINVAL)
if (rc == -EINVAL || rc == -ENXIO)
return 0;
/*
* If we got -EAGAIN here, we simply return it. It will eventually

1
arch/s390/kvm/kvm-s390.c
View file

@ -50,6 +50,7 @@
#include "kvm-s390.h"
#include "gaccess.h"
#include "pci.h"
#include "gmap.h"
#define CREATE_TRACE_POINTS
#include "trace.h"

21
arch/s390/kvm/pv.c
View file

@ -17,6 +17,7 @@
#include <linux/sched/mm.h>
#include <linux/mmu_notifier.h>
#include "kvm-s390.h"
#include "gmap.h"
bool kvm_s390_pv_is_protected(struct kvm *kvm)
{
@ -638,10 +639,28 @@ static int unpack_one(struct kvm *kvm, unsigned long addr, u64 tweak,
.tweak[1] = offset,
};
int ret = gmap_make_secure(kvm->arch.gmap, addr, &uvcb);
unsigned long vmaddr;
bool unlocked;
*rc = uvcb.header.rc;
*rrc = uvcb.header.rrc;
if (ret == -ENXIO) {
mmap_read_lock(kvm->mm);
vmaddr = gfn_to_hva(kvm, gpa_to_gfn(addr));
if (kvm_is_error_hva(vmaddr)) {
ret = -EFAULT;
} else {
ret = fixup_user_fault(kvm->mm, vmaddr, FAULT_FLAG_WRITE, &unlocked);
if (!ret)
ret = __gmap_link(kvm->arch.gmap, addr, vmaddr);
}
mmap_read_unlock(kvm->mm);
if (!ret)
return -EAGAIN;
return ret;
}
if (ret && ret != -EAGAIN)
KVM_UV_EVENT(kvm, 3, "PROTVIRT VM UNPACK: failed addr %llx with rc %x rrc %x",
uvcb.gaddr, *rc, *rrc);
@ -660,6 +679,8 @@ int kvm_s390_pv_unpack(struct kvm *kvm, unsigned long addr, unsigned long size,
KVM_UV_EVENT(kvm, 3, "PROTVIRT VM UNPACK: start addr %lx size %lx",
addr, size);
guard(srcu)(&kvm->srcu);
while (offset < size) {
ret = unpack_one(kvm, addr, tweak, offset, rc, rrc);
if (ret == -EAGAIN) {

28
arch/s390/mm/gmap.c
View file

@ -3035,3 +3035,31 @@ int s390_replace_asce(struct gmap *gmap)
return 0;
}
EXPORT_SYMBOL_GPL(s390_replace_asce);
/**
* kvm_s390_wiggle_split_folio() - try to drain extra references to a folio and optionally split
* @mm: the mm containing the folio to work on
* @folio: the folio
* @split: whether to split a large folio
*
* Context: Must be called while holding an extra reference to the folio;
* the mm lock should not be held.
*/
int kvm_s390_wiggle_split_folio(struct mm_struct *mm, struct folio *folio, bool split)
{
int rc;
lockdep_assert_not_held(&mm->mmap_lock);
folio_wait_writeback(folio);
lru_add_drain_all();
if (split) {
folio_lock(folio);
rc = split_folio(folio);
folio_unlock(folio);
if (rc != -EBUSY)
return rc;
}
return -EAGAIN;
}
EXPORT_SYMBOL_GPL(kvm_s390_wiggle_split_folio);