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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
Subject: [PATCH v2 06/13] KVM: s390: pv: refactor s390_reset_acc
Date: Wed, 28 Jul 2021 16:26:24 +0200	[thread overview]
Message-ID: <20210728142631.41860-7-imbrenda@linux.ibm.com> (raw)
In-Reply-To: <20210728142631.41860-1-imbrenda@linux.ibm.com>

Refactor s390_reset_acc so that its pieces can be reused in upcoming
patches. The users parameter for s390_destroy_range will be needed in
upcoming patches.

We don't want to hold all the locks used in a walk_page_range for too
long, and the destroy page UVC does take some time to complete.
Therefore we quickly gather the pages to destroy, and then destroy them
without holding all the locks.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/include/asm/gmap.h |  5 +-
 arch/s390/kvm/pv.c           | 12 ++++-
 arch/s390/mm/gmap.c          | 88 ++++++++++++++++++++++++------------
 3 files changed, 73 insertions(+), 32 deletions(-)

diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
index 40264f60b0da..618ddc455867 100644
--- a/arch/s390/include/asm/gmap.h
+++ b/arch/s390/include/asm/gmap.h
@@ -147,5 +147,8 @@ int gmap_mprotect_notify(struct gmap *, unsigned long start,
 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_uv_destroy_range(struct mm_struct *mm, unsigned int users,
+			   unsigned long start, unsigned long end);
+void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns);
+
 #endif /* _ASM_S390_GMAP_H */
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 1ecdc1769ed9..ebb1c8d7bcb3 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -12,6 +12,8 @@
 #include <asm/gmap.h>
 #include <asm/uv.h>
 #include <asm/mman.h>
+#include <linux/pagewalk.h>
+#include <linux/sched/mm.h>
 #include "kvm-s390.h"
 
 int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc)
@@ -209,8 +211,14 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 {
 	int cc;
 
-	/* make all pages accessible before destroying the guest */
-	s390_reset_acc(kvm->mm);
+	/*
+	 * if the mm still has a mapping, make all its pages accessible
+	 * before destroying the guest
+	 */
+	if (mmget_not_zero(kvm->mm)) {
+		s390_uv_destroy_range(kvm->mm, 0, 0, TASK_SIZE);
+		mmput(kvm->mm);
+	}
 
 	cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
 			   UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index de679facc720..ad210a6e2c41 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2670,41 +2670,71 @@ void s390_reset_cmma(struct mm_struct *mm)
 }
 EXPORT_SYMBOL_GPL(s390_reset_cmma);
 
-/*
- * make inaccessible pages accessible again
- */
-static int __s390_reset_acc(pte_t *ptep, unsigned long addr,
-			    unsigned long next, struct mm_walk *walk)
+#define DESTROY_LOOP_THRESHOLD 32
+
+struct reset_walk_state {
+	unsigned long next;
+	unsigned long count;
+	unsigned long pfns[DESTROY_LOOP_THRESHOLD];
+};
+
+static int s390_gather_pages(pte_t *ptep, unsigned long addr,
+			     unsigned long next, struct mm_walk *walk)
 {
+	struct reset_walk_state *p = walk->private;
 	pte_t pte = READ_ONCE(*ptep);
 
-	/* There is a reference through the mapping */
-	if (pte_present(pte))
-		WARN_ON_ONCE(uv_destroy_owned_page(pte_val(pte) & PAGE_MASK));
-
-	return 0;
+	if (pte_present(pte)) {
+		/* we have a reference from the mapping, take an extra one */
+		get_page(phys_to_page(pte_val(pte)));
+		p->pfns[p->count] = phys_to_pfn(pte_val(pte));
+		p->next = next;
+		p->count++;
+	}
+	return p->count >= DESTROY_LOOP_THRESHOLD;
 }
 
-static const struct mm_walk_ops reset_acc_walk_ops = {
-	.pte_entry		= __s390_reset_acc,
+static const struct mm_walk_ops gather_pages_ops = {
+	.pte_entry = s390_gather_pages,
 };
 
-#include <linux/sched/mm.h>
-void s390_reset_acc(struct mm_struct *mm)
+/*
+ * Call the Destroy secure page UVC on each page in the given array of PFNs.
+ * Each page needs to have an extra reference, which will be released here.
+ */
+void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns)
 {
-	if (!mm_is_protected(mm))
-		return;
-	/*
-	 * we might be called during
-	 * reset:                             we walk the pages and clear
-	 * close of all kvm file descriptors: we walk the pages and clear
-	 * exit of process on fd closure:     vma already gone, do nothing
-	 */
-	if (!mmget_not_zero(mm))
-		return;
-	mmap_read_lock(mm);
-	walk_page_range(mm, 0, TASK_SIZE, &reset_acc_walk_ops, NULL);
-	mmap_read_unlock(mm);
-	mmput(mm);
+	unsigned long i;
+
+	for (i = 0; i < count; i++) {
+		/* we always have an extra reference */
+		uv_destroy_owned_page(pfn_to_phys(pfns[i]));
+		/* get rid of the extra reference */
+		put_page(pfn_to_page(pfns[i]));
+		cond_resched();
+	}
+}
+EXPORT_SYMBOL_GPL(s390_uv_destroy_pfns);
+
+/*
+ * Walk the given range of the given address space, and call the destroy
+ * secure page UVC on each page.
+ * Exit early if the number of users of the mm drops to (or below) the given
+ * value.
+ */
+void s390_uv_destroy_range(struct mm_struct *mm, unsigned int users,
+			   unsigned long start, unsigned long end)
+{
+	struct reset_walk_state state = { .next = start };
+	int r = 1;
+
+	while ((r > 0) && (atomic_read(&mm->mm_users) > users)) {
+		state.count = 0;
+		mmap_read_lock(mm);
+		r = walk_page_range(mm, state.next, end, &gather_pages_ops, &state);
+		mmap_read_unlock(mm);
+		cond_resched();
+		s390_uv_destroy_pfns(state.count, state.pfns);
+	}
 }
-EXPORT_SYMBOL_GPL(s390_reset_acc);
+EXPORT_SYMBOL_GPL(s390_uv_destroy_range);
-- 
2.31.1


  parent reply	other threads:[~2021-07-28 14:27 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-28 14:26 [PATCH v2 00/13] KVM: s390: pv: implement lazy destroy Claudio Imbrenda
2021-07-28 14:26 ` [PATCH v2 01/13] KVM: s390: pv: avoid stall notifications for some UVCs Claudio Imbrenda
2021-07-29  9:58   ` Janosch Frank
2021-07-29 12:52     ` Claudio Imbrenda
2021-07-29 10:49   ` Cornelia Huck
2021-07-29 13:22     ` Claudio Imbrenda
2021-07-28 14:26 ` [PATCH v2 02/13] KVM: s390: pv: leak the ASCE page when destroy fails Claudio Imbrenda
2021-07-29 10:41   ` Janosch Frank
2021-07-29 12:54     ` Claudio Imbrenda
2021-07-29 13:45       ` Janosch Frank
2021-07-28 14:26 ` [PATCH v2 03/13] KVM: s390: pv: properly handle page flags for protected guests Claudio Imbrenda
2021-07-29 11:43   ` Janosch Frank
2021-07-28 14:26 ` [PATCH v2 04/13] KVM: s390: pv: handle secure storage violations " Claudio Imbrenda
2021-07-28 14:26 ` [PATCH v2 05/13] KVM: s390: pv: handle secure storage exceptions for normal guests Claudio Imbrenda
2021-07-29 12:17   ` Janosch Frank
2021-07-29 13:28     ` Claudio Imbrenda
2021-07-28 14:26 ` Claudio Imbrenda [this message]
2021-07-28 14:26 ` [PATCH v2 07/13] KVM: s390: pv: usage counter instead of flag Claudio Imbrenda
2021-07-28 14:26 ` [PATCH v2 08/13] KVM: s390: pv: add export before import Claudio Imbrenda
2021-07-28 14:26 ` [PATCH v2 09/13] KVM: s390: pv: lazy destroy for reboot Claudio Imbrenda
2021-07-28 14:26 ` [PATCH v2 10/13] KVM: s390: pv: extend lazy destroy to handle shutdown Claudio Imbrenda
2021-07-28 14:26 ` [PATCH v2 11/13] KVM: s390: pv: module parameter to fence lazy destroy Claudio Imbrenda
2021-07-28 14:26 ` [PATCH v2 12/13] KVM: s390: pv: add OOM notifier for " Claudio Imbrenda
2021-07-28 14:26 ` [PATCH v2 13/13] KVM: s390: pv: add support for UV feature bits Claudio Imbrenda
2021-07-29  9:52   ` Janosch Frank
2021-07-29 13:28     ` Claudio Imbrenda

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