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KVM: s390: Fall back to short-term pinning in MAP ioctl

Browse Source 
JIRA: https://redhat.atlassian.net/browse/RHEL-136457

Upstream Status: https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux.git

commit 9972befc3e34ff8b6847198c84f11bfc312dde40
Author: Jaehoon Kim <jhkim@linux.ibm.com>
Date:   Fri Jul 24 08:39:43 2026 -0500

    KVM: s390: Fall back to short-term pinning in MAP ioctl

    FOLL_LONGTERM pinning fails for some memory types, such as file-backed
    guest memory. As a result, kvm_s390_adapter_map() returns -EINVAL and
    irqfd adapter registration fails even though interrupt delivery could
    still work via the existing non-atomic path.

    When FOLL_LONGTERM pinning fails, verify that the page is accessible
    using a short-term pin instead. If the short-term pin succeeds, unpin
    the page and add a map entry with pinned=false to preserve MAP/UNMAP
    symmetry. The non-atomic irqfd path already performs short-term pinning
    for interrupt delivery, so this restores the previous behavior for
    memory that cannot be pinned long-term.

    get_map_info() is updated to return NULL for unpinned entries so that
    the atomic irqfd fast path falls back to the non-atomic path.
    kvm_s390_adapter_unmap() and kvm_s390_unmap_all_adapters() skip dirty
    marking and unpin for unpinned entries.

    Update Documentation/virt/kvm/devices/s390_flic.rst to reflect the
    new MAP/UNMAP behavior.

    Fixes: c9a568838086 ("KVM: s390: Add map/unmap ioctl and clean mappings post-guest")
    Signed-off-by: Jaehoon Kim <jhkim@linux.ibm.com>
    Reviewed-by: Douglas Freimuth <freimuth@linux.ibm.com>
    Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
    Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>

Signed-off-by: Christoph Schlameuss <cschlame@redhat.com>
This commit is contained in:
Christoph Schlameuss
2026-08-04 17:57:33 +02:00
parent 7bfce03eb0
commit 4c5b31c6a0
3 changed files with 60 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Documentation/virt/kvm/devices/s390_flic.rst
+13 -2
View File
@@ -112,9 +112,20 @@ Groups:
mask or unmask the adapter, as specified in mask
KVM_S390_IO_ADAPTER_MAP
This is now a no-op. The mapping is purely done by the irq route.
Map an adapter indicator or summary page for long-term pinning so that
interrupt injection can be performed in atomic context. If long-term
pinning is not possible (e.g. file-backed memory), the page is verified
via a short-term pin and the ioctl returns success; interrupt injection
will use the non-atomic irqfd path with short-term pinning on each
interrupt. In Secure Execution mode this is a no-op and the ioctl
returns success.
KVM_S390_IO_ADAPTER_UNMAP
This is now a no-op. The mapping is purely done by the irq route.
Unmap a previously mapped adapter indicator or summary page and release
the long-term pin. If the page was not long-term pinned (e.g. file-backed
memory), the map entry is removed and success is returned; if no prior
map entry exists, -ENOENT is returned. In Secure Execution mode this is
a no-op and the ioctl returns success.
KVM_DEV_FLIC_AISM
modify the adapter-interruption-suppression mode for a given isc if the
arch/s390/include/asm/kvm_host.h
+5
View File
@@ -470,6 +470,11 @@ struct s390_map_info {
__u64 guest_addr;
__u64 addr;
struct page *page;
/*
* True if the page is long-term pinned. False if long-term pinning
* failed and this entry exists only to preserve MAP/UNMAP symmetry.
*/
bool pinned;
};
struct s390_io_adapter {
arch/s390/kvm/interrupt.c
+42 -14
View File
@@ -2565,8 +2565,22 @@ static int kvm_s390_adapter_map(struct kvm *kvm, unsigned int id, __u64 addr)
map->addr = host_addr;
map->page = pin_map_page(kvm, host_addr, FOLL_LONGTERM);
if (!map->page) {
ret = -EINVAL;
goto out;
/*
* Long-term pinning may fail for memory types such as file-backed
* memory. Verify that short-term pinning succeeds so that the
* non-atomic irqfd path can handle interrupt injection.
*/
map->page = pin_map_page(kvm, host_addr, 0);
if (!map->page) {
ret = -EINVAL;
goto out;
}
unpin_user_page(map->page);
map->page = NULL;
map->pinned = false;
/* Add an entry to preserve MAP/UNMAP symmetry. */
} else {
map->pinned = true;
}
spin_lock_irqsave(&adapter->maps_lock, flags);
if (adapter->nr_maps < MAX_S390_ADAPTER_MAPS) {
@@ -2577,7 +2591,7 @@ static int kvm_s390_adapter_map(struct kvm *kvm, unsigned int id, __u64 addr)
ret = -EINVAL;
}
spin_unlock_irqrestore(&adapter->maps_lock, flags);
if (ret)
if (ret && map->page)
unpin_user_page(map->page);
out:
if (ret)
@@ -2591,6 +2605,7 @@ static int kvm_s390_adapter_unmap(struct kvm *kvm, unsigned int id, __u64 addr)
struct s390_map_info *map, *tmp, *map_to_free;
struct page *map_page_to_put = NULL;
u64 map_addr_to_mark = 0;
bool map_pinned = false;
unsigned long flags;
int found = 0, idx;
@@ -2605,6 +2620,7 @@ static int kvm_s390_adapter_unmap(struct kvm *kvm, unsigned int id, __u64 addr)
list_del(&map->list);
map_page_to_put = map->page;
map_addr_to_mark = map->guest_addr;
map_pinned = map->pinned;
map_to_free = map;
break;
}
@@ -2613,11 +2629,18 @@ static int kvm_s390_adapter_unmap(struct kvm *kvm, unsigned int id, __u64 addr)
if (found) {
kfree(map_to_free);
idx = srcu_read_lock(&kvm->srcu);
mark_page_dirty(kvm, map_addr_to_mark >> PAGE_SHIFT);
set_page_dirty_lock(map_page_to_put);
srcu_read_unlock(&kvm->srcu, idx);
unpin_user_page(map_page_to_put);
if (map_pinned) {
/*
* Only long-term pinned pages need to be marked dirty
* and released. Fallback entries exist only for
* MAP/UNMAP symmetry.
*/
idx = srcu_read_lock(&kvm->srcu);
mark_page_dirty(kvm, map_addr_to_mark >> PAGE_SHIFT);
set_page_dirty_lock(map_page_to_put);
srcu_read_unlock(&kvm->srcu, idx);
unpin_user_page(map_page_to_put);
}
}
return found ? 0 : -ENOENT;
@@ -2643,11 +2666,13 @@ void kvm_s390_unmap_all_adapters(struct kvm *kvm)
list_for_each_entry_safe(map, tmp, &local_list, list) {
list_del(&map->list);
idx = srcu_read_lock(&kvm->srcu);
mark_page_dirty(kvm, map->guest_addr >> PAGE_SHIFT);
set_page_dirty_lock(map->page);
srcu_read_unlock(&kvm->srcu, idx);
unpin_user_page(map->page);
if (map->pinned) {
idx = srcu_read_lock(&kvm->srcu);
mark_page_dirty(kvm, map->guest_addr >> PAGE_SHIFT);
set_page_dirty_lock(map->page);
srcu_read_unlock(&kvm->srcu, idx);
unpin_user_page(map->page);
}
kfree(map);
}
}
@@ -2974,8 +2999,11 @@ static struct s390_map_info *get_map_info(struct s390_io_adapter *adapter,
return NULL;
list_for_each_entry(map, &adapter->maps, list) {
if (map->addr == addr)
if (map->addr == addr) {
if (!map->pinned)
return NULL;
return map;
}
}
return NULL;
}