Re: [PATCH 1/2] KVM: Mark KVM_SET_MEMORY_REGION and KVM_SET_MEMORY_ALIAS as obsoleted

From: Sean Christopherson
Date: Mon Nov 28 2022 - 13:33:32 EST


On Sat, Nov 19, 2022, Javier Martinez Canillas wrote:
> Other ioctl such as KVM_ARM_SET_DEVICE_ADDR have a (deprecated) next to it
> which makes it easier to determine that is deprecated. Do the same for the
> ioctls that have been obsoleted.
>
> Suggested-by: Sergio Lopez Pascual <slp@xxxxxxxxxx>
> Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
> ---
>
> Documentation/virt/kvm/api.rst | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index eee9f857a986..c17bac32d25c 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -272,7 +272,7 @@ the VCPU file descriptor can be mmap-ed, including:
> KVM_CAP_DIRTY_LOG_RING, see section 8.3.
>
>
> -4.6 KVM_SET_MEMORY_REGION
> +4.6 KVM_SET_MEMORY_REGION (obsoleted)

I realize the existing doc entry and include/uapi/linux/kvm.h says these are
"obsolete", but both of these are more than just obsolete since KVM no longer
supports them. There's even a different blurb that states they are deprecated.

E.g. KVM_{CREATE,GET,SET}_PIT are good examples of obsolete ioctls; they've been
supplanted by newer variants, but KVM still supports the old ones too.

Alternatively (to marking them deprecated), can we completely remove all references
to VM_SET_MEMORY_REGION and KVM_SET_MEMORY_ALIAS? The cascading updates in api.rst
will be painful, but it's one-time pain.

E.g. can we do something like this?

---
Documentation/virt/kvm/api.rst | 27 ---------------------------
arch/x86/include/uapi/asm/kvm.h | 8 --------
include/uapi/linux/kvm.h | 12 ++----------
3 files changed, 2 insertions(+), 45 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index eee9f857a986..85a5b12eb017 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -272,18 +272,6 @@ the VCPU file descriptor can be mmap-ed, including:
KVM_CAP_DIRTY_LOG_RING, see section 8.3.


-4.6 KVM_SET_MEMORY_REGION
--------------------------
-
-:Capability: basic
-:Architectures: all
-:Type: vm ioctl
-:Parameters: struct kvm_memory_region (in)
-:Returns: 0 on success, -1 on error
-
-This ioctl is obsolete and has been removed.
-
-
4.7 KVM_CREATE_VCPU
-------------------

@@ -368,17 +356,6 @@ see the description of the capability.
Note that the Xen shared info page, if configured, shall always be assumed
to be dirty. KVM will not explicitly mark it such.

-4.9 KVM_SET_MEMORY_ALIAS
-------------------------
-
-:Capability: basic
-:Architectures: x86
-:Type: vm ioctl
-:Parameters: struct kvm_memory_alias (in)
-:Returns: 0 (success), -1 (error)
-
-This ioctl is obsolete and has been removed.
-

4.10 KVM_RUN
------------
@@ -1377,10 +1354,6 @@ the memory region are automatically reflected into the guest. For example, an
mmap() that affects the region will be made visible immediately. Another
example is madvise(MADV_DROP).

-It is recommended to use this API instead of the KVM_SET_MEMORY_REGION ioctl.
-The KVM_SET_MEMORY_REGION does not allow fine grained control over memory
-allocation and is deprecated.
-

4.36 KVM_SET_TSS_ADDR
---------------------
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index c6df6b16a088..e48deab8901d 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -53,14 +53,6 @@
/* Architectural interrupt line count. */
#define KVM_NR_INTERRUPTS 256

-struct kvm_memory_alias {
- __u32 slot; /* this has a different namespace than memory slots */
- __u32 flags;
- __u64 guest_phys_addr;
- __u64 memory_size;
- __u64 target_phys_addr;
-};
-
/* for KVM_GET_IRQCHIP and KVM_SET_IRQCHIP */
struct kvm_pic_state {
__u8 last_irr; /* edge detection */
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 7fea12369245..b8e905ac9d0d 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -86,13 +86,6 @@ struct kvm_debug_guest {
/* *** End of deprecated interfaces *** */


-/* for KVM_CREATE_MEMORY_REGION */
-struct kvm_memory_region {
- __u32 slot;
- __u32 flags;
- __u64 guest_phys_addr;
- __u64 memory_size; /* bytes */
-};

/* for KVM_SET_USER_MEMORY_REGION */
struct kvm_userspace_memory_region {
@@ -1443,15 +1436,14 @@ struct kvm_vfio_spapr_tce {
/*
* ioctls for VM fds
*/
-#define KVM_SET_MEMORY_REGION _IOW(KVMIO, 0x40, struct kvm_memory_region)
+#define KVM_DEPRECATED_SET_MEMORY_REGION _IOW(KVMIO, 0x40)
/*
* KVM_CREATE_VCPU receives as a parameter the vcpu slot, and returns
* a vcpu fd.
*/
#define KVM_CREATE_VCPU _IO(KVMIO, 0x41)
#define KVM_GET_DIRTY_LOG _IOW(KVMIO, 0x42, struct kvm_dirty_log)
-/* KVM_SET_MEMORY_ALIAS is obsolete: */
-#define KVM_SET_MEMORY_ALIAS _IOW(KVMIO, 0x43, struct kvm_memory_alias)
+#define KVM_DEPRECATED_SET_MEMORY_ALIAS _IOW(KVMIO, 0x43)
#define KVM_SET_NR_MMU_PAGES _IO(KVMIO, 0x44)
#define KVM_GET_NR_MMU_PAGES _IO(KVMIO, 0x45)
#define KVM_SET_USER_MEMORY_REGION _IOW(KVMIO, 0x46, \

base-commit: 7ca560b50ba9a13150ccf2768ae1f53cd6c735c1
--