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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>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Marc Zyngier" <marc.zyngier@arm.com>
Cc: Wanpeng Li <wanpengli@tencent.com>,
	kvm@vger.kernel.org, David Hildenbrand <david@redhat.com>,
	linux-arm-kernel@lists.infradead.org,
	Joerg Roedel <joro@8bytes.org>, Cornelia Huck <cohuck@redhat.com>,
	linux-mips@vger.kernel.org,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	kvmarm@lists.cs.columbia.edu, Jim Mattson <jmattson@google.com>
Subject: [PATCH 09/13] KVM: Clean up local variable usage in __kvm_set_memory_region()
Date: Wed, 11 Sep 2019 11:50:34 -0700
Message-ID: <20190911185038.24341-10-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20190911185038.24341-1-sean.j.christopherson@intel.com>

Clean up __kvm_set_memory_region() to achieve several goals:

  - Remove local variables that serve no real purpose
  - Improve the readability of the code
  - Better show the relationship between the 'old' and 'new' memslot
  - Prepare for dynamically sizing memslots.

Note, using 'tmp' to hold the initial memslot is not strictly necessary
at this juncture, e.g. 'old' could be directly copied from
id_to_memslot(), but keep the pointer usage as id_to_memslot() will be
able to return a NULL pointer once memslots are dynamically sized.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 virt/kvm/kvm_main.c | 47 +++++++++++++++++++++++----------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8f2f4ee32f3e..0e46524487cc 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -995,13 +995,11 @@ static int kvm_delete_memslot(struct kvm *kvm,
 int __kvm_set_memory_region(struct kvm *kvm,
 			    const struct kvm_userspace_memory_region *mem)
 {
-	int r;
-	gfn_t base_gfn;
-	unsigned long npages;
-	struct kvm_memory_slot *slot;
 	struct kvm_memory_slot old, new;
-	int as_id, id;
+	struct kvm_memory_slot *tmp;
 	enum kvm_mr_change change;
+	int as_id, id;
+	int r;
 
 	r = check_memory_region_flags(mem);
 	if (r)
@@ -1026,52 +1024,55 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
 		return -EINVAL;
 
-	slot = id_to_memslot(__kvm_memslots(kvm, as_id), id);
-	base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
-	npages = mem->memory_size >> PAGE_SHIFT;
-
-	if (npages > KVM_MEM_MAX_NR_PAGES)
-		return -EINVAL;
-
 	/*
 	 * Make a full copy of the old memslot, the pointer will become stale
 	 * when the memslots are re-sorted by update_memslots().
 	 */
-	old = *slot;
+	tmp = id_to_memslot(__kvm_memslots(kvm, as_id), id);
+	old = *tmp;
+	tmp = NULL;
+
 	if (!mem->memory_size)
 		return kvm_delete_memslot(kvm, mem, &old, as_id);
 
-	new = old;
-
 	new.id = id;
-	new.base_gfn = base_gfn;
-	new.npages = npages;
+	new.base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
+	new.npages = mem->memory_size >> PAGE_SHIFT;
 	new.flags = mem->flags;
 	new.userspace_addr = mem->userspace_addr;
 
+	if (new.npages > KVM_MEM_MAX_NR_PAGES)
+		return -EINVAL;
+
 	if (!old.npages) {
 		change = KVM_MR_CREATE;
+		new.dirty_bitmap = NULL;
+		memset(&new.arch, 0, sizeof(new.arch));
 	} else { /* Modify an existing slot. */
 		if ((new.userspace_addr != old.userspace_addr) ||
-		    (npages != old.npages) ||
+		    (new.npages != old.npages) ||
 		    ((new.flags ^ old.flags) & KVM_MEM_READONLY))
 			return -EINVAL;
 
-		if (base_gfn != old.base_gfn)
+		if (new.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;
+
+		/* Copy dirty_bitmap and arch from the current memslot. */
+		new.dirty_bitmap = old.dirty_bitmap;
+		memcpy(&new.arch, &old.arch, sizeof(new.arch));
 	}
 
 	if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
 		/* Check for overlaps */
-		kvm_for_each_memslot(slot, __kvm_memslots(kvm, as_id)) {
-			if (slot->id == id)
+		kvm_for_each_memslot(tmp, __kvm_memslots(kvm, as_id)) {
+			if (tmp->id == id)
 				continue;
-			if (!((base_gfn + npages <= slot->base_gfn) ||
-			      (base_gfn >= slot->base_gfn + slot->npages)))
+			if (!((new.base_gfn + new.npages <= tmp->base_gfn) ||
+			      (new.base_gfn >= tmp->base_gfn + tmp->npages)))
 				return -EEXIST;
 		}
 	}
-- 
2.22.0

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  parent reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-11 18:50 [PATCH 00/13] KVM: Dynamically size memslot arrays Sean Christopherson
2019-09-11 18:50 ` [PATCH 01/13] KVM: Reinstall old memslots if arch preparation fails Sean Christopherson
2019-09-11 18:50 ` [PATCH 02/13] KVM: PPC: Move memslot memory allocation into prepare_memory_region() Sean Christopherson
2019-09-19  0:23   ` Paul Mackerras
2019-09-11 18:50 ` [PATCH 03/13] KVM: x86: Allocate memslot resources during prepare_memory_region() Sean Christopherson
2019-09-11 18:50 ` [PATCH 04/13] KVM: Drop kvm_arch_create_memslot() Sean Christopherson
2019-09-12 11:31   ` Janosch Frank
2019-09-11 18:50 ` [PATCH 05/13] KVM: Refactor error handling for setting memory region Sean Christopherson
2019-09-12 11:36   ` Janosch Frank
2019-09-11 18:50 ` [PATCH 06/13] KVM: Move setting of memslot into helper routine Sean Christopherson
2019-09-11 18:50 ` [PATCH 07/13] KVM: Move memslot deletion to helper function Sean Christopherson
2019-09-11 18:50 ` [PATCH 08/13] KVM: Simplify kvm_free_memslot() and all its descendents Sean Christopherson
2019-09-11 18:50 ` Sean Christopherson [this message]
2019-09-11 18:50 ` [PATCH 10/13] KVM: Provide common implementation for generic dirty log functions Sean Christopherson
2019-09-19  0:22   ` Paul Mackerras
2019-09-19 19:39     ` Sean Christopherson
2019-09-11 18:50 ` [PATCH 11/13] KVM: Ensure validity of memslot with respect to kvm_get_dirty_log() Sean Christopherson
2019-09-11 18:50 ` [PATCH 12/13] KVM: Terminate memslot walks via used_slots Sean Christopherson
2019-09-11 18:50 ` [PATCH 13/13] KVM: Dynamically size memslot array based on number of used slots Sean Christopherson

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