In case of memory pressure, it's possible that a guest page gets freed
and then almost immediately reused by the guest. If CMMA is enabled,
_essa_clear_cbrl() will discard all pages that are either unused or
zero. If a discarded page is reused before _essa_clear_cbrl() is called,
and the pgste.zero bit is not cleared, the page will be discarded
despite not being unused.
When calling _gmap_ptep_xchg(), always clear the pgste.zero bit. This
prevents the page from being accidentally discarded when not unused.
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Fixes: a2c17f9270 ("KVM: s390: New gmap code")
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
In some cases (i.e. under extreme memory pressure on the host),
attempting to shadow memory will result in the same memory being
unshadowed, causing a loop.
Add a PGSTE bit to distinguish between shadowed memory and shadowed DAT
tables, fix the unshadowing logic in _gmap_ptep_xchg() to prevent
unnecessary unshadowing and perform better checks.
Also fix the unshadowing logic in _gmap_crstep_xchg_atomic() which did
not unshadow properly when the large page would become unprotected.
Opportunistically add a check in gmap_protect_rmap() to make sure it
won't be called with level == TABLE_TYPE_PAGE_TABLE.
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Fixes: a2c17f9270 ("KVM: s390: New gmap code")
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Introduce a new boolean flag, used for shadow gmaps, to keep track of
whether the gmap has been invalidated, either partially or totally.
Use the new flag to check whether shadow gmap invalidations happened
during shadowing. In such cases, abort whatever was going on, return
-EAGAIN and let the caller try again.
Fixes: 19d6c5b804 ("KVM: s390: vsie: Fix unshadowing while shadowing")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260407161721.247044-1-imbrenda@linux.ibm.com>
When backing a guest page with a large page, check that the alignment
of the guest page matches the alignment of the host physical page
backing it within the large page.
Also check that the memslot is large enough to fit the large page.
Those checks are currently not needed, because memslots are guaranteed
to be 1m-aligned, but this will change.
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Introduce a new special softbit for large pages, like already presend
for normal pages, and use it to mark guest mappings that do not have
struct pages.
Whenever a leaf DAT entry becomes dirty, check the special softbit and
only call SetPageDirty() if there is an actual struct page.
Move the logic to mark pages dirty inside _gmap_ptep_xchg() and
_gmap_crstep_xchg_atomic(), to avoid needlessly duplicating the code.
Fixes: 5a74e3d934 ("KVM: s390: KVM-specific bitfields and helper functions")
Fixes: a2c17f9270 ("KVM: s390: New gmap code")
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
In practice dat_crstep_xchg() is racy and hard to use correctly. Simply
remove it and replace its uses with dat_crstep_xchg_atomic().
This solves some actual races that lead to system hangs / crashes.
Opportunistically fix an alignment issue in _gmap_crstep_xchg_atomic().
Fixes: 589071eaaa ("KVM: s390: KVM page table management functions: clear and replace")
Fixes: 94fd9b16cc ("KVM: s390: KVM page table management functions: lifecycle management")
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
New gmap (guest map) code. This new gmap code will only be used by KVM.
This will replace the existing gmap.
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
All functions in kvm/gmap.c fit better in kvm/pv.c instead.
Move and rename them appropriately, then delete the now empty
kvm/gmap.c and kvm/gmap.h.
Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20250528095502.226213-5-imbrenda@linux.ibm.com
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20250528095502.226213-5-imbrenda@linux.ibm.com>
Move some gmap shadowing functions from mm/gmap.c to kvm/kvm-s390.c and
the newly created kvm/gmap-vsie.c
This is a step toward removing gmap from mm.
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Link: https://lore.kernel.org/r/20250123144627.312456-10-imbrenda@linux.ibm.com
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20250123144627.312456-10-imbrenda@linux.ibm.com>
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>
