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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: James Hogan <jhogan@kernel.org>,
	Paul Mackerras <paulus@ozlabs.org>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Janosch Frank <frankja@linux.ibm.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Marc Zyngier <maz@kernel.org>
Cc: "David Hildenbrand" <david@redhat.com>,
	"Cornelia Huck" <cohuck@redhat.com>,
	"Sean Christopherson" <sean.j.christopherson@intel.com>,
	"Vitaly Kuznetsov" <vkuznets@redhat.com>,
	"Wanpeng Li" <wanpengli@tencent.com>,
	"Jim Mattson" <jmattson@google.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	"James Morse" <james.morse@arm.com>,
	"Julien Thierry" <julien.thierry.kdev@gmail.com>,
	"Suzuki K Poulose" <suzuki.poulose@arm.com>,
	linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org,
	kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
	"Christoffer Dall" <christoffer.dall@arm.com>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>
Subject: [PATCH v4 12/19] KVM: Move memslot deletion to helper function
Date: Tue, 17 Dec 2019 12:40:34 -0800
Message-ID: <20191217204041.10815-13-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20191217204041.10815-1-sean.j.christopherson@intel.com>

Move memslot deletion into its own routine so that the success path for
other memslot updates does not need to use kvm_free_memslot(), i.e. can
explicitly destroy the dirty bitmap when necessary.  This paves the way
for dropping @dont from kvm_free_memslot(), i.e. all callers now pass
NULL for @dont.

Add a comment above the code to make a copy of the existing memslot
prior to deletion, it is not at all obvious that the pointer will become
stale during sorting and/or installation of new memslots.

Note, kvm_arch_commit_memory_region() allows an architecture to free
resources when moving a memslot or changing its flags, e.g. x86 frees
its arch specific memslot metadata during commit_memory_region().

Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Tested-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 virt/kvm/kvm_main.c | 73 +++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 29 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index acf52fa16500..50e5aec0c15c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1046,6 +1046,27 @@ static int kvm_set_memslot(struct kvm *kvm,
 	return r;
 }
 
+static int kvm_delete_memslot(struct kvm *kvm,
+			      const struct kvm_userspace_memory_region *mem,
+			      struct kvm_memory_slot *old, int as_id)
+{
+	struct kvm_memory_slot new;
+	int r;
+
+	if (!old->npages)
+		return -EINVAL;
+
+	memset(&new, 0, sizeof(new));
+	new.id = old->id;
+
+	r = kvm_set_memslot(kvm, mem, old, &new, as_id, KVM_MR_DELETE);
+	if (r)
+		return r;
+
+	kvm_free_memslot(kvm, old, NULL);
+	return 0;
+}
+
 /*
  * Allocate some memory and give it an address in the guest physical address
  * space.
@@ -1095,7 +1116,15 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	if (npages > KVM_MEM_MAX_NR_PAGES)
 		return -EINVAL;
 
-	new = old = *slot;
+	/*
+	 * Make a full copy of the old memslot, the pointer will become stale
+	 * when the memslots are re-sorted by update_memslots().
+	 */
+	old = *slot;
+	if (!mem->memory_size)
+		return kvm_delete_memslot(kvm, mem, &old, as_id);
+
+	new = old;
 
 	new.id = id;
 	new.base_gfn = base_gfn;
@@ -1103,29 +1132,20 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	new.flags = mem->flags;
 	new.userspace_addr = mem->userspace_addr;
 
-	if (npages) {
-		if (!old.npages)
-			change = KVM_MR_CREATE;
-		else { /* Modify an existing slot. */
-			if ((new.userspace_addr != old.userspace_addr) ||
-			    (npages != old.npages) ||
-			    ((new.flags ^ old.flags) & KVM_MEM_READONLY))
-				return -EINVAL;
-
-			if (base_gfn != old.base_gfn)
-				change = KVM_MR_MOVE;
-			else if (new.flags != old.flags)
-				change = KVM_MR_FLAGS_ONLY;
-			else /* Nothing to change. */
-				return 0;
-		}
-	} else {
-		if (!old.npages)
+	if (!old.npages) {
+		change = KVM_MR_CREATE;
+	} else { /* Modify an existing slot. */
+		if ((new.userspace_addr != old.userspace_addr) ||
+		    (npages != old.npages) ||
+		    ((new.flags ^ old.flags) & KVM_MEM_READONLY))
 			return -EINVAL;
 
-		change = KVM_MR_DELETE;
-		new.base_gfn = 0;
-		new.flags = 0;
+		if (base_gfn != old.base_gfn)
+			change = KVM_MR_MOVE;
+		else if (new.flags != old.flags)
+			change = KVM_MR_FLAGS_ONLY;
+		else /* Nothing to change. */
+			return 0;
 	}
 
 	if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
@@ -1148,17 +1168,12 @@ int __kvm_set_memory_region(struct kvm *kvm,
 			return r;
 	}
 
-	/* actual memory is freed via old in kvm_free_memslot below */
-	if (change == KVM_MR_DELETE) {
-		new.dirty_bitmap = NULL;
-		memset(&new.arch, 0, sizeof(new.arch));
-	}
-
 	r = kvm_set_memslot(kvm, mem, &old, &new, as_id, change);
 	if (r)
 		goto out_bitmap;
 
-	kvm_free_memslot(kvm, &old, &new);
+	if (old.dirty_bitmap && !new.dirty_bitmap)
+		kvm_destroy_dirty_bitmap(&old);
 	return 0;
 
 out_bitmap:
-- 
2.24.1


  parent reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17 20:40 [PATCH v4 00/19] KVM: Dynamically size memslot arrays Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 01/19] KVM: x86: Allocate new rmap and large page tracking when moving memslot Sean Christopherson
2019-12-17 20:48   ` Sean Christopherson
2019-12-17 20:50     ` Sean Christopherson
2019-12-17 21:56   ` Peter Xu
2019-12-17 22:20     ` Sean Christopherson
2019-12-17 22:37       ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 02/19] KVM: Reinstall old memslots if arch preparation fails Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 03/19] KVM: Don't free new memslot if allocation of said memslot fails Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 04/19] KVM: PPC: Move memslot memory allocation into prepare_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 05/19] KVM: x86: Allocate memslot resources during prepare_memory_region() Sean Christopherson
2019-12-17 22:07   ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 06/19] KVM: Drop kvm_arch_create_memslot() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 07/19] KVM: Explicitly free allocated-but-unused dirty bitmap Sean Christopherson
2019-12-17 22:24   ` Peter Xu
2019-12-17 22:51     ` Sean Christopherson
2019-12-18 16:17       ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 08/19] KVM: Refactor error handling for setting memory region Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 09/19] KVM: Move setting of memslot into helper routine Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 10/19] KVM: Drop "const" attribute from old memslot in commit_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 11/19] KVM: x86: Free arrays for old memslot when moving memslot's base gfn Sean Christopherson
2019-12-17 22:48   ` Peter Xu
2019-12-17 20:40 ` Sean Christopherson [this message]
2019-12-17 20:40 ` [PATCH v4 13/19] KVM: Simplify kvm_free_memslot() and all its descendents Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 14/19] KVM: Clean up local variable usage in __kvm_set_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 15/19] KVM: Provide common implementation for generic dirty log functions Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 16/19] KVM: Ensure validity of memslot with respect to kvm_get_dirty_log() Sean Christopherson
2019-12-24 18:19   ` Peter Xu
2020-01-14 18:25     ` Sean Christopherson
2020-02-06 22:03       ` Peter Xu
2020-02-07 18:52         ` Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 17/19] KVM: Terminate memslot walks via used_slots Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 18/19] KVM: Dynamically size memslot array based on number of used slots Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 19/19] KVM: selftests: Add test for KVM_SET_USER_MEMORY_REGION Sean Christopherson
2019-12-18 11:29   ` Christian Borntraeger
2019-12-18 11:39   ` Christian Borntraeger
2019-12-18 16:39     ` Sean Christopherson
2019-12-18 11:40 ` [PATCH v4 00/19] KVM: Dynamically size memslot arrays Christian Borntraeger
2019-12-18 18:10 ` Marc Zyngier

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