On 20.11.2012, at 09:57, Paul Mackerras wrote:
> A new ioctl, KVM_PPC_GET_HTAB_FD, returns a file descriptor. Reads on
> this fd return the contents of the HPT (hashed page table), writes
> create and/or remove entries in the HPT. There is a new capability,
> KVM_CAP_PPC_HTAB_FD, to indicate the presence of the ioctl. The ioctl
> takes an argument structure with the index of the first HPT entry to
> read out and a set of flags. The flags indicate whether the user is
> intending to read or write the HPT, and whether to return all entries
> or only the "bolted" entries (those with the bolted bit, 0x10, set in
> the first doubleword).
>
> This is intended for use in implementing qemu's savevm/loadvm and for
> live migration. Therefore, on reads, the first pass returns information
> about all HPTEs (or all bolted HPTEs). When the first pass reaches the
> end of the HPT, it returns from the read. Subsequent reads only return
> information about HPTEs that have changed since they were last read.
> A read that finds no changed HPTEs in the HPT following where the last
> read finished will return 0 bytes.
>
> The format of the data provides a simple run-length compression of the
> invalid entries. Each block of data starts with a header that indicates
> the index (position in the HPT, which is just an array), the number of
> valid entries starting at that index (may be zero), and the number of
> invalid entries following those valid entries. The valid entries, 16
> bytes each, follow the header. The invalid entries are not explicitly
> represented.
>
> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx>
> ---
> v2: added comments, added reserved field in struct kvm_get_htab_fd
>
> Documentation/virtual/kvm/api.txt | 53 +++++
> arch/powerpc/include/asm/kvm_book3s_64.h | 22 ++
> arch/powerpc/include/asm/kvm_ppc.h | 2 +
> arch/powerpc/include/uapi/asm/kvm.h | 25 +++
> arch/powerpc/kvm/book3s_64_mmu_hv.c | 344 ++++++++++++++++++++++++++++++
> arch/powerpc/kvm/book3s_hv.c | 12 --
> arch/powerpc/kvm/powerpc.c | 17 ++
> include/uapi/linux/kvm.h | 3 +
> 8 files changed, 466 insertions(+), 12 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 6671fdc..33080ea 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2071,6 +2071,59 @@ KVM_S390_INT_EXTERNAL_CALL (vcpu) - sigp external call; source cpu in parm
>
> Note that the vcpu ioctl is asynchronous to vcpu execution.
>
> +4.78 KVM_PPC_GET_HTAB_FD
> +
> +Capability: KVM_CAP_PPC_HTAB_FD
> +Architectures: powerpc
> +Type: vm ioctl
> +Parameters: Pointer to struct kvm_get_htab_fd (in)
> +Returns: file descriptor number (>= 0) on success, -1 on error
> +
> +This returns a file descriptor that can be used either to read out the
> +entries in the guest's hashed page table (HPT), or to write entries to
> +initialize the HPT. The returned fd can only be written to if the
> +KVM_GET_HTAB_WRITE bit is set in the flags field of the argument, and
> +can only be read if that bit is clear. The argument struct looks like
> +this:
> +
> +/* For KVM_PPC_GET_HTAB_FD */
> +struct kvm_get_htab_fd {
> + __u64 flags;
> + __u64 start_index;
Documentation is out of sync :).
Applied all 3 with fixed documentation.
Alex
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