[PATCH 04/13] KVM: Drop kvm_arch_create_memslot()

Sean Christopherson
2019-09-11T18:51:31Z

Remove kvm_arch_create_memslot() now that all arch implementations are
effectively nops. Explicitly free an allocated-but-unused dirty bitmap
instead of relying on kvm_free_memslot() now that setting a memslot can
no longer fail after arch code has allocated memory. In practice
this was already true, e.g. architectures that allocated memory via
kvm_arch_create_memslot() never failed kvm_arch_prepare_memory_region()
and vice versa, but removing kvm_arch_create_memslot() eliminates the
potential for future code to stealthily change behavior.

Eliminating the error path's reliance on kvm_free_memslot() paves the
way for simplify kvm_free_memslot(), i.e. dropping its @dont param.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/mips/kvm/mips.c | 6 ------
arch/powerpc/kvm/powerpc.c | 6 ------
arch/s390/kvm/kvm-s390.c | 6 ------
arch/x86/kvm/x86.c | 6 ------
include/linux/kvm_host.h | 2 --
virt/kvm/arm/mmu.c | 6 ------
virt/kvm/kvm_main.c | 28 +++++++++++-----------------
7 files changed, 11 insertions(+), 49 deletions(-)

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 1109924560d8..713e5465edb0 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -188,12 +188,6 @@ long kvm_arch_dev_ioctl(struct file *filp, unsigned int ioctl,
return -ENOIOCTLCMD;
}

-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
- unsigned long npages)
-{
- return 0;
-}
-
void kvm_arch_flush_shadow_all(struct kvm *kvm)
{
/* Flush whole GPA */
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 8b723b164fe1..cf74bf8f921a 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -686,12 +686,6 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
kvmppc_core_free_memslot(kvm, free, dont);
}

-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
- unsigned long npages)
-{
- return 0;
-}
-
int kvm_arch_prepare_memory_region(struct kvm *kvm,
struct kvm_memory_slot *memslot,
const struct kvm_userspace_memory_region *mem,
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index f329dcb3f44c..e651ed80dc2c 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4488,12 +4488,6 @@ vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
return VM_FAULT_SIGBUS;
}

-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
- unsigned long npages)
-{
- return 0;
-}
-
/* Section: memory related */
int kvm_arch_prepare_memory_region(struct kvm *kvm,
struct kvm_memory_slot *memslot,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 72ec6272d7cb..7adde30c1305 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9482,12 +9482,6 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
kvm_page_track_free_memslot(free, dont);
}

-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
- unsigned long npages)
-{
- return 0;
-}
-
static int kvm_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
unsigned long npages)
{
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index fcb46b3374c6..cce72f55ab76 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -679,8 +679,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
const struct kvm_userspace_memory_region *mem);
void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
struct kvm_memory_slot *dont);
-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
- unsigned long npages);
void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen);
int kvm_arch_prepare_memory_region(struct kvm *kvm,
struct kvm_memory_slot *memslot,
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 38b4c910b6c3..f264de85f648 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -2358,12 +2358,6 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
{
}

-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
- unsigned long npages)
-{
- return 0;
-}
-
void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen)
{
}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index daa5de5b3f88..ea8f2f37096f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -964,12 +964,13 @@ int __kvm_set_memory_region(struct kvm *kvm,
new.base_gfn = base_gfn;
new.npages = npages;
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 ((mem->userspace_addr != old.userspace_addr) ||
+ if ((new.userspace_addr != old.userspace_addr) ||
(npages != old.npages) ||
((new.flags ^ old.flags) & KVM_MEM_READONLY))
goto out;
@@ -1004,27 +1005,19 @@ int __kvm_set_memory_region(struct kvm *kvm,
}
}

- /* Free page dirty bitmap if unneeded */
+ r = -ENOMEM;
+
+ /* Allocate/free page dirty bitmap as needed */
if (!(new.flags & KVM_MEM_LOG_DIRTY_PAGES))
new.dirty_bitmap = NULL;
-
- r = -ENOMEM;
- if (change == KVM_MR_CREATE) {
- new.userspace_addr = mem->userspace_addr;
-
- if (kvm_arch_create_memslot(kvm, &new, npages))
- goto out_free;
- }
-
- /* Allocate page dirty bitmap if needed */
- if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) {
+ else if (!new.dirty_bitmap) {
if (kvm_create_dirty_bitmap(&new) < 0)
- goto out_free;
+ goto out;
}

slots = kvzalloc(sizeof(struct kvm_memslots), GFP_KERNEL_ACCOUNT);
if (!slots)
- goto out_free;
+ goto out_bitmap;
memcpy(slots, __kvm_memslots(kvm, as_id), sizeof(struct kvm_memslots));

if ((change == KVM_MR_DELETE) || (change == KVM_MR_MOVE)) {
@@ -1072,8 +1065,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
if (change == KVM_MR_DELETE || change == KVM_MR_MOVE)
slots = install_new_memslots(kvm, as_id, slots);
kvfree(slots);
-out_free:
- kvm_free_memslot(kvm, &new, &old);
+out_bitmap:
+ if (new.dirty_bitmap && !old.dirty_bitmap)
+ kvm_destroy_dirty_bitmap(&new);
out:
return r;
}
--
2.22.0