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Wed, 18 Aug 2021 13:26:24 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DC07F4C050; Wed, 18 Aug 2021 13:26:23 +0000 (GMT) Received: from p-imbrenda.bredband2.com (unknown [9.145.14.177]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 18 Aug 2021 13:26:23 +0000 (GMT) From: Claudio Imbrenda To: kvm@vger.kernel.org Cc: cohuck@redhat.com, borntraeger@de.ibm.com, frankja@linux.ibm.com, thuth@redhat.com, pasic@linux.ibm.com, david@redhat.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Ulrich.Weigand@de.ibm.com Subject: [PATCH v4 05/14] KVM: s390: pv: leak the ASCE page when destroy fails Date: Wed, 18 Aug 2021 15:26:11 +0200 Message-Id: <20210818132620.46770-6-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210818132620.46770-1-imbrenda@linux.ibm.com> References: <20210818132620.46770-1-imbrenda@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 035iyZJkmzpwP9ANpc0uRlnm_aM_Weg- X-Proofpoint-GUID: c7MRnumkwfA5jLSgeFmAKB-2erH11Ysl X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-18_04:2021-08-17,2021-08-18 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 lowpriorityscore=0 phishscore=0 malwarescore=0 mlxscore=0 bulkscore=0 impostorscore=0 suspectscore=0 spamscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108180082 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a protected VM is created, the topmost level of page tables of its ASCE is marked by the Ultravisor; any attempt to use that memory for protected virtualization will result in failure. Only a successful Destroy Configuration UVC will remove the marking. When the Destroy Configuration UVC fails, the topmost level of page tables of the VM does not get its marking cleared; to avoid issues it must not be used again. This is a permanent error and the page becomes in practice unusable, so we set it aside and leak it. Signed-off-by: Claudio Imbrenda --- arch/s390/include/asm/gmap.h | 2 ++ arch/s390/kvm/pv.c | 4 ++- arch/s390/mm/gmap.c | 55 ++++++++++++++++++++++++++++++++++++ 3 files changed, 60 insertions(+), 1 deletion(-) diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h index 40264f60b0da..746e18bf8984 100644 --- a/arch/s390/include/asm/gmap.h +++ b/arch/s390/include/asm/gmap.h @@ -148,4 +148,6 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4], unsigned long gaddr, unsigned long vmaddr); int gmap_mark_unmergeable(void); void s390_reset_acc(struct mm_struct *mm); +void s390_remove_old_asce(struct gmap *gmap); +int s390_replace_asce(struct gmap *gmap); #endif /* _ASM_S390_GMAP_H */ diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c index 00d272d134c2..76b0d64ce8fa 100644 --- a/arch/s390/kvm/pv.c +++ b/arch/s390/kvm/pv.c @@ -168,9 +168,11 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc) atomic_set(&kvm->mm->context.is_protected, 0); KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc); WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc); - /* Inteded memory leak on "impossible" error */ + /* Intended memory leak on "impossible" error */ if (!cc) kvm_s390_pv_dealloc_vm(kvm); + else + s390_replace_asce(kvm->arch.gmap); return cc ? -EIO : 0; } diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c index 9bb2c7512cd5..5a138f6220c4 100644 --- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -2706,3 +2706,58 @@ void s390_reset_acc(struct mm_struct *mm) mmput(mm); } EXPORT_SYMBOL_GPL(s390_reset_acc); + +/* + * Remove the topmost level of page tables from the list of page tables of + * the gmap. + * This means that it will not be freed when the VM is torn down, and needs + * to be handled separately by the caller, unless an intentional leak is + * intended. + */ +void s390_remove_old_asce(struct gmap *gmap) +{ + struct page *old; + + old = virt_to_page(gmap->table); + spin_lock(&gmap->guest_table_lock); + list_del(&old->lru); + spin_unlock(&gmap->guest_table_lock); + /* in case the ASCE needs to be "removed" multiple times */ + INIT_LIST_HEAD(&old->lru); +} +EXPORT_SYMBOL_GPL(s390_remove_old_asce); + +/* + * Try to replace the current ASCE with another equivalent one. + * If the allocation of the new top level page table fails, the ASCE is not + * replaced. + * In any case, the old ASCE is removed from the list, therefore the caller + * has to make sure to save a pointer to it beforehands, unless an + * intentional leak is intended. + */ +int s390_replace_asce(struct gmap *gmap) +{ + unsigned long asce; + struct page *page; + void *table; + + s390_remove_old_asce(gmap); + + page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER); + if (!page) + return -ENOMEM; + table = page_to_virt(page); + memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT)); + + spin_lock(&gmap->guest_table_lock); + list_add(&page->lru, &gmap->crst_list); + spin_unlock(&gmap->guest_table_lock); + + asce = (gmap->asce & ~PAGE_MASK) | __pa(table); + WRITE_ONCE(gmap->asce, asce); + WRITE_ONCE(gmap->mm->context.gmap_asce, asce); + WRITE_ONCE(gmap->table, table); + + return 0; +} +EXPORT_SYMBOL_GPL(s390_replace_asce); -- 2.31.1