KVM: Allow 2048-bit register access via ioctl interface

The Arm SVE architecture defines registers that are up to 2048 bits
in size (with some possibility of further future expansion).

In order to avoid the need for an excessively large number of
ioctls when saving and restoring a vcpu's registers, this patch
adds a #define to make support for individual 2048-bit registers
through the KVM_{GET,SET}_ONE_REG ioctl interface official.  This
will allow each SVE register to be accessed in a single call.

There are sufficient spare bits in the register id size field for
this change, so there is no ABI impact, providing that
KVM_GET_REG_LIST does not enumerate any 2048-bit register unless
userspace explicitly opts in to the relevant architecture-specific
features.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 6d4ea4b6c92206ac5843c258f5c1f56987d79f0e..dc77a5a3648d0c3dc7ced284fed1fef5adecef1c 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1145,6 +1145,7 @@ struct kvm_dirty_tlb {
 #define KVM_REG_SIZE_U256      0x0050000000000000ULL
 #define KVM_REG_SIZE_U512      0x0060000000000000ULL
 #define KVM_REG_SIZE_U1024     0x0070000000000000ULL
+#define KVM_REG_SIZE_U2048     0x0080000000000000ULL
 
 struct kvm_reg_list {
        __u64 n; /* number of regs */