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From: Claudio Imbrenda <imbrenda@linux.ibm.com>
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	[thread overview]
Message-ID: <20210818132620.46770-6-imbrenda@linux.ibm.com> (raw)
In-Reply-To: <20210818132620.46770-1-imbrenda@linux.ibm.com>

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 <imbrenda@linux.ibm.com>
---
 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


  parent reply	other threads:[~2021-08-18 13:27 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 13:26 [PATCH v4 00/14] KVM: s390: pv: implement lazy destroy for reboot Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 01/14] KVM: s390: pv: add macros for UVC CC values Claudio Imbrenda
2021-08-31 13:43   ` Christian Borntraeger
2021-08-18 13:26 ` [PATCH v4 02/14] KVM: s390: pv: avoid double free of sida page Claudio Imbrenda
2021-08-31 13:55   ` Christian Borntraeger
2021-09-08 18:50     ` Claudio Imbrenda
2021-08-31 13:59   ` Janosch Frank
2021-08-18 13:26 ` [PATCH v4 03/14] KVM: s390: pv: avoid stalls for kvm_s390_pv_init_vm Claudio Imbrenda
2021-08-31 14:10   ` Christian Borntraeger
2021-08-18 13:26 ` [PATCH v4 04/14] KVM: s390: pv: avoid stalls when making pages secure Claudio Imbrenda
2021-08-31 14:32   ` Christian Borntraeger
2021-08-31 15:00     ` Claudio Imbrenda
2021-08-31 15:11       ` Christian Borntraeger
2021-08-18 13:26 ` Claudio Imbrenda [this message]
2021-09-06 15:32   ` [PATCH v4 05/14] KVM: s390: pv: leak the ASCE page when destroy fails Christian Borntraeger
2021-09-06 15:54     ` Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 06/14] KVM: s390: pv: properly handle page flags for protected guests Claudio Imbrenda
2021-09-06 15:46   ` Christian Borntraeger
2021-09-06 15:56     ` Claudio Imbrenda
2021-09-06 16:16       ` Christian Borntraeger
2021-09-17 14:57         ` Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 07/14] KVM: s390: pv: handle secure storage violations " Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 08/14] KVM: s390: pv: handle secure storage exceptions for normal guests Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 09/14] KVM: s390: pv: refactor s390_reset_acc Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 10/14] KVM: s390: pv: usage counter instead of flag Claudio Imbrenda
2021-08-26  7:58   ` Janis Schoetterl-Glausch
2021-08-18 13:26 ` [PATCH v4 11/14] KVM: s390: pv: add export before import Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 12/14] KVM: s390: pv: module parameter to fence lazy destroy Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 13/14] KVM: s390: pv: lazy destroy for reboot Claudio Imbrenda
2021-08-26  8:33   ` Janis Schoetterl-Glausch
2021-08-18 13:26 ` [PATCH v4 14/14] KVM: s390: pv: avoid export before import if possible Claudio Imbrenda

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