Re: [PATCH V4 14/24] arm/ioreq: Introduce arch specific bits for IOREQ/DM features

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 12 Jan 2021, Oleksandr Tyshchenko wrote:
> From: Julien Grall <julien.grall@xxxxxxx>
> 
> This patch adds basic IOREQ/DM support on Arm. The subsequent
> patches will improve functionality and add remaining bits.
> 
> The IOREQ/DM features are supposed to be built with IOREQ_SERVER
> option enabled, which is disabled by default on Arm for now.
> 
> Please note, the "PIO handling" TODO is expected to left unaddressed
> for the current series. It is not an big issue for now while Xen
> doesn't have support for vPCI on Arm. On Arm64 they are only used
> for PCI IO Bar and we would probably want to expose them to emulator
> as PIO access to make a DM completely arch-agnostic. So "PIO handling"
> should be implemented when we add support for vPCI.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> [On Arm only]
> Tested-by: Wei Chen <Wei.Chen@xxxxxxx>
> 
> ---
> Please note, this is a split/cleanup/hardening of Julien's PoC:
> "Add support for Guest IO forwarding to a device emulator"
> 
> Changes RFC -> V1:
>    - was split into:
>      - arm/ioreq: Introduce arch specific bits for IOREQ/DM features
>      - xen/mm: Handle properly reference in set_foreign_p2m_entry() on Arm
>    - update patch description
>    - update asm-arm/hvm/ioreq.h according to the newly introduced arch 
> functions:
>      - arch_hvm_destroy_ioreq_server()
>      - arch_handle_hvm_io_completion()
>    - update arch files to include xen/ioreq.h
>    - remove HVMOP plumbing
>    - rewrite a logic to handle properly case when hvm_send_ioreq() returns 
> IO_RETRY
>    - add a logic to handle properly handle_hvm_io_completion() return value
>    - rename handle_mmio() to ioreq_handle_complete_mmio()
>    - move paging_mark_pfn_dirty() to asm-arm/paging.h
>    - remove forward declaration for hvm_ioreq_server in asm-arm/paging.h
>    - move try_fwd_ioserv() to ioreq.c, provide stubs if !CONFIG_IOREQ_SERVER
>    - do not remove #ifdef CONFIG_IOREQ_SERVER in memory.c for guarding 
> xen/ioreq.h
>    - use gdprintk in try_fwd_ioserv(), remove unneeded prints
>    - update list of #include-s
>    - move has_vpci() to asm-arm/domain.h
>    - add a comment (TODO) to unimplemented yet handle_pio()
>    - remove hvm_mmio_first(last)_byte() and hvm_ioreq_(page/vcpu/server) 
> structs
>      from the arch files, they were already moved to the common code
>    - remove set_foreign_p2m_entry() changes, they will be properly implemented
>      in the follow-up patch
>    - select IOREQ_SERVER for Arm instead of Arm64 in Kconfig
>    - remove x86's realmode and other unneeded stubs from xen/ioreq.h
>    - clafify ioreq_t p.df usage in try_fwd_ioserv()
>    - set ioreq_t p.count to 1 in try_fwd_ioserv()
> 
> Changes V1 -> V2:
>    - was split into:
>      - arm/ioreq: Introduce arch specific bits for IOREQ/DM features
>      - xen/arm: Stick around in leave_hypervisor_to_guest until I/O has 
> completed
>    - update the author of a patch
>    - update patch description
>    - move a loop in leave_hypervisor_to_guest() to a separate patch
>    - set IOREQ_SERVER disabled by default
>    - remove already clarified /* XXX */
>    - replace BUG() by ASSERT_UNREACHABLE() in handle_pio()
>    - remove default case for handling the return value of try_handle_mmio()
>    - remove struct hvm_domain, enum hvm_io_completion, struct hvm_vcpu_io,
>      struct hvm_vcpu from asm-arm/domain.h, these are common materials now
>    - update everything according to the recent changes (IOREQ related function
>      names don't contain "hvm" prefixes/infixes anymore, IOREQ related fields
>      are part of common struct vcpu/domain now, etc)
> 
> Changes V2 -> V3:
>    - update patch according the "legacy interface" is x86 specific
>    - add dummy arch hooks
>    - remove dummy paging_mark_pfn_dirty()
>    - don’t include <xen/domain_page.h> in common ioreq.c
>    - don’t include <public/hvm/ioreq.h> in arch ioreq.h
>    - remove #define ioreq_params(d, i)
> 
> Changes V3 -> V4:
>    - rebase
>    - update patch according to the renaming IO_ -> VIO_ (io_ -> vio_)
>      and misc changes to arch hooks
>    - update patch according to the IOREQ related dm-op handling changes
>    - don't include <xen/ioreq.h> from arch header
>    - make all arch hooks out-of-line
>    - add a comment above IOREQ_STATUS_* #define-s
> ---
>  xen/arch/arm/Makefile           |   2 +
>  xen/arch/arm/dm.c               | 122 +++++++++++++++++++++++
>  xen/arch/arm/domain.c           |   9 ++
>  xen/arch/arm/io.c               |  12 ++-
>  xen/arch/arm/ioreq.c            | 213 
> ++++++++++++++++++++++++++++++++++++++++
>  xen/arch/arm/traps.c            |  13 +++
>  xen/include/asm-arm/domain.h    |   3 +
>  xen/include/asm-arm/hvm/ioreq.h |  72 ++++++++++++++
>  xen/include/asm-arm/mmio.h      |   1 +
>  9 files changed, 446 insertions(+), 1 deletion(-)
>  create mode 100644 xen/arch/arm/dm.c
>  create mode 100644 xen/arch/arm/ioreq.c
>  create mode 100644 xen/include/asm-arm/hvm/ioreq.h
> 
> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
> index 512ffdd..16e6523 100644
> --- a/xen/arch/arm/Makefile
> +++ b/xen/arch/arm/Makefile
> @@ -13,6 +13,7 @@ obj-y += cpuerrata.o
>  obj-y += cpufeature.o
>  obj-y += decode.o
>  obj-y += device.o
> +obj-$(CONFIG_IOREQ_SERVER) += dm.o
>  obj-y += domain.o
>  obj-y += domain_build.init.o
>  obj-y += domctl.o
> @@ -27,6 +28,7 @@ obj-y += guest_atomics.o
>  obj-y += guest_walk.o
>  obj-y += hvm.o
>  obj-y += io.o
> +obj-$(CONFIG_IOREQ_SERVER) += ioreq.o
>  obj-y += irq.o
>  obj-y += kernel.init.o
>  obj-$(CONFIG_LIVEPATCH) += livepatch.o
> diff --git a/xen/arch/arm/dm.c b/xen/arch/arm/dm.c
> new file mode 100644
> index 0000000..e6dedf4
> --- /dev/null
> +++ b/xen/arch/arm/dm.c
> @@ -0,0 +1,122 @@
> +/*
> + * Copyright (c) 2019 Arm ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along 
> with
> + * this program; If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <xen/dm.h>
> +#include <xen/guest_access.h>
> +#include <xen/hypercall.h>
> +#include <xen/ioreq.h>
> +#include <xen/nospec.h>
> +
> +static int dm_op(const struct dmop_args *op_args)
> +{
> +    struct domain *d;
> +    struct xen_dm_op op;
> +    bool const_op = true;
> +    long rc;
> +    size_t offset;
> +
> +    static const uint8_t op_size[] = {
> +        [XEN_DMOP_create_ioreq_server]              = sizeof(struct 
> xen_dm_op_create_ioreq_server),
> +        [XEN_DMOP_get_ioreq_server_info]            = sizeof(struct 
> xen_dm_op_get_ioreq_server_info),
> +        [XEN_DMOP_map_io_range_to_ioreq_server]     = sizeof(struct 
> xen_dm_op_ioreq_server_range),
> +        [XEN_DMOP_unmap_io_range_from_ioreq_server] = sizeof(struct 
> xen_dm_op_ioreq_server_range),
> +        [XEN_DMOP_set_ioreq_server_state]           = sizeof(struct 
> xen_dm_op_set_ioreq_server_state),
> +        [XEN_DMOP_destroy_ioreq_server]             = sizeof(struct 
> xen_dm_op_destroy_ioreq_server),
> +    };
> +
> +    rc = rcu_lock_remote_domain_by_id(op_args->domid, &d);
> +    if ( rc )
> +        return rc;
> +
> +    rc = xsm_dm_op(XSM_DM_PRIV, d);
> +    if ( rc )
> +        goto out;
> +
> +    offset = offsetof(struct xen_dm_op, u);
> +
> +    rc = -EFAULT;
> +    if ( op_args->buf[0].size < offset )
> +        goto out;
> +
> +    if ( copy_from_guest_offset((void *)&op, op_args->buf[0].h, 0, offset) )
> +        goto out;
> +
> +    if ( op.op >= ARRAY_SIZE(op_size) )
> +    {
> +        rc = -EOPNOTSUPP;
> +        goto out;
> +    }
> +
> +    op.op = array_index_nospec(op.op, ARRAY_SIZE(op_size));
> +
> +    if ( op_args->buf[0].size < offset + op_size[op.op] )
> +        goto out;
> +
> +    if ( copy_from_guest_offset((void *)&op.u, op_args->buf[0].h, offset,
> +                                op_size[op.op]) )
> +        goto out;
> +
> +    rc = -EINVAL;
> +    if ( op.pad )
> +        goto out;
> +
> +    rc = ioreq_server_dm_op(&op, d, &const_op);
> +
> +    if ( (!rc || rc == -ERESTART) &&
> +         !const_op && copy_to_guest_offset(op_args->buf[0].h, offset,
> +                                           (void *)&op.u, op_size[op.op]) )
> +        rc = -EFAULT;
> +
> + out:
> +    rcu_unlock_domain(d);
> +
> +    return rc;
> +}
> +
> +long do_dm_op(domid_t domid,
> +              unsigned int nr_bufs,
> +              XEN_GUEST_HANDLE_PARAM(xen_dm_op_buf_t) bufs)
> +{
> +    struct dmop_args args;
> +    int rc;
> +
> +    if ( nr_bufs > ARRAY_SIZE(args.buf) )
> +        return -E2BIG;
> +
> +    args.domid = domid;
> +    args.nr_bufs = array_index_nospec(nr_bufs, ARRAY_SIZE(args.buf) + 1);
> +
> +    if ( copy_from_guest_offset(&args.buf[0], bufs, 0, args.nr_bufs) )
> +        return -EFAULT;
> +
> +    rc = dm_op(&args);
> +
> +    if ( rc == -ERESTART )
> +        rc = hypercall_create_continuation(__HYPERVISOR_dm_op, "iih",
> +                                           domid, nr_bufs, bufs);
> +
> +    return rc;
> +}

I might have missed something in the discussions but this function is
identical to xen/arch/x86/hvm/dm.c:do_dm_op, why not make it common?

Also the previous function dm_op is very similar to
xen/arch/x86/hvm/dm.c:dm_op I would prefer to make them common if
possible. Was this already discussed?


> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * tab-width: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index 18cafcd..8f55aba 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -15,6 +15,7 @@
>  #include <xen/guest_access.h>
>  #include <xen/hypercall.h>
>  #include <xen/init.h>
> +#include <xen/ioreq.h>
>  #include <xen/lib.h>
>  #include <xen/livepatch.h>
>  #include <xen/sched.h>
> @@ -696,6 +697,10 @@ int arch_domain_create(struct domain *d,
>  
>      ASSERT(config != NULL);
>  
> +#ifdef CONFIG_IOREQ_SERVER
> +    ioreq_domain_init(d);
> +#endif
> +
>      /* p2m_init relies on some value initialized by the IOMMU subsystem */
>      if ( (rc = iommu_domain_init(d, config->iommu_opts)) != 0 )
>          goto fail;
> @@ -1014,6 +1019,10 @@ int domain_relinquish_resources(struct domain *d)
>          if (ret )
>              return ret;
>  
> +#ifdef CONFIG_IOREQ_SERVER
> +        ioreq_server_destroy_all(d);
> +#endif
> +
>      PROGRESS(xen):
>          ret = relinquish_memory(d, &d->xenpage_list);
>          if ( ret )
> diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
> index ae7ef96..9814481 100644
> --- a/xen/arch/arm/io.c
> +++ b/xen/arch/arm/io.c
> @@ -16,6 +16,7 @@
>   * GNU General Public License for more details.
>   */
>  
> +#include <xen/ioreq.h>
>  #include <xen/lib.h>
>  #include <xen/spinlock.h>
>  #include <xen/sched.h>
> @@ -23,6 +24,7 @@
>  #include <asm/cpuerrata.h>
>  #include <asm/current.h>
>  #include <asm/mmio.h>
> +#include <asm/hvm/ioreq.h>
>  
>  #include "decode.h"
>  
> @@ -123,7 +125,15 @@ enum io_state try_handle_mmio(struct cpu_user_regs *regs,
>  
>      handler = find_mmio_handler(v->domain, info.gpa);
>      if ( !handler )
> -        return IO_UNHANDLED;
> +    {
> +        int rc;
> +
> +        rc = try_fwd_ioserv(regs, v, &info);
> +        if ( rc == IO_HANDLED )
> +            return handle_ioserv(regs, v);
> +
> +        return rc;
> +    }
>  
>      /* All the instructions used on emulated MMIO region should be valid */
>      if ( !dabt.valid )
> diff --git a/xen/arch/arm/ioreq.c b/xen/arch/arm/ioreq.c
> new file mode 100644
> index 0000000..3c4a24d
> --- /dev/null
> +++ b/xen/arch/arm/ioreq.c
> @@ -0,0 +1,213 @@
> +/*
> + * arm/ioreq.c: hardware virtual machine I/O emulation
> + *
> + * Copyright (c) 2019 Arm ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along 
> with
> + * this program; If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <xen/domain.h>
> +#include <xen/ioreq.h>
> +
> +#include <asm/traps.h>
> +
> +#include <public/hvm/ioreq.h>
> +
> +enum io_state handle_ioserv(struct cpu_user_regs *regs, struct vcpu *v)
> +{
> +    const union hsr hsr = { .bits = regs->hsr };
> +    const struct hsr_dabt dabt = hsr.dabt;
> +    /* Code is similar to handle_read */
> +    uint8_t size = (1 << dabt.size) * 8;
> +    register_t r = v->io.req.data;
> +
> +    /* We are done with the IO */
> +    v->io.req.state = STATE_IOREQ_NONE;
> +
> +    if ( dabt.write )
> +        return IO_HANDLED;
> +
> +    /*
> +     * Sign extend if required.
> +     * Note that we expect the read handler to have zeroed the bits
> +     * outside the requested access size.
> +     */
> +    if ( dabt.sign && (r & (1UL << (size - 1))) )
> +    {
> +        /*
> +         * We are relying on register_t using the same as
> +         * an unsigned long in order to keep the 32-bit assembly
> +         * code smaller.
> +         */
> +        BUILD_BUG_ON(sizeof(register_t) != sizeof(unsigned long));
> +        r |= (~0UL) << size;
> +    }
> +
> +    set_user_reg(regs, dabt.reg, r);
> +
> +    return IO_HANDLED;
> +}
> +
> +enum io_state try_fwd_ioserv(struct cpu_user_regs *regs,
> +                             struct vcpu *v, mmio_info_t *info)
> +{
> +    struct vcpu_io *vio = &v->io;
> +    ioreq_t p = {
> +        .type = IOREQ_TYPE_COPY,
> +        .addr = info->gpa,
> +        .size = 1 << info->dabt.size,
> +        .count = 1,
> +        .dir = !info->dabt.write,
> +        /*
> +         * On x86, df is used by 'rep' instruction to tell the direction
> +         * to iterate (forward or backward).
> +         * On Arm, all the accesses to MMIO region will do a single
> +         * memory access. So for now, we can safely always set to 0.
> +         */
> +        .df = 0,
> +        .data = get_user_reg(regs, info->dabt.reg),
> +        .state = STATE_IOREQ_READY,
> +    };
> +    struct ioreq_server *s = NULL;
> +    enum io_state rc;
> +
> +    switch ( vio->req.state )
> +    {
> +    case STATE_IOREQ_NONE:
> +        break;
> +
> +    case STATE_IORESP_READY:
> +        return IO_HANDLED;
> +
> +    default:
> +        gdprintk(XENLOG_ERR, "wrong state %u\n", vio->req.state);
> +        return IO_ABORT;
> +    }
> +
> +    s = ioreq_server_select(v->domain, &p);
> +    if ( !s )
> +        return IO_UNHANDLED;
> +
> +    if ( !info->dabt.valid )
> +        return IO_ABORT;
> +
> +    vio->req = p;
> +
> +    rc = ioreq_send(s, &p, 0);
> +    if ( rc != IO_RETRY || v->domain->is_shutting_down )
> +        vio->req.state = STATE_IOREQ_NONE;
> +    else if ( !ioreq_needs_completion(&vio->req) )
> +        rc = IO_HANDLED;
> +    else
> +        vio->completion = VIO_mmio_completion;
> +
> +    return rc;
> +}
> +
> +bool arch_ioreq_complete_mmio(void)
> +{
> +    struct vcpu *v = current;
> +    struct cpu_user_regs *regs = guest_cpu_user_regs();
> +    const union hsr hsr = { .bits = regs->hsr };
> +    paddr_t addr = v->io.req.addr;
> +
> +    if ( try_handle_mmio(regs, hsr, addr) == IO_HANDLED )
> +    {
> +        advance_pc(regs, hsr);
> +        return true;
> +    }
> +
> +    return false;
> +}
> +
> +bool arch_vcpu_ioreq_completion(enum vio_completion completion)
> +{
> +    ASSERT_UNREACHABLE();
> +    return true;
> +}
> +
> +/*
> + * The "legacy" mechanism of mapping magic pages for the IOREQ servers
> + * is x86 specific, so the following hooks don't need to be implemented on 
> Arm:
> + * - arch_ioreq_server_map_pages
> + * - arch_ioreq_server_unmap_pages
> + * - arch_ioreq_server_enable
> + * - arch_ioreq_server_disable
> + */
> +int arch_ioreq_server_map_pages(struct ioreq_server *s)
> +{
> +    return -EOPNOTSUPP;
> +}
> +
> +void arch_ioreq_server_unmap_pages(struct ioreq_server *s)
> +{
> +}
> +
> +void arch_ioreq_server_enable(struct ioreq_server *s)
> +{
> +}
> +
> +void arch_ioreq_server_disable(struct ioreq_server *s)
> +{
> +}
> +
> +void arch_ioreq_server_destroy(struct ioreq_server *s)
> +{
> +}
> +
> +int arch_ioreq_server_map_mem_type(struct domain *d,
> +                                   struct ioreq_server *s,
> +                                   uint32_t flags)
> +{
> +    return -EOPNOTSUPP;
> +}
> +
> +void arch_ioreq_server_map_mem_type_completed(struct domain *d,
> +                                              struct ioreq_server *s,
> +                                              uint32_t flags)
> +{
> +}
> +
> +bool arch_ioreq_server_destroy_all(struct domain *d)
> +{
> +    return true;
> +}
> +
> +bool arch_ioreq_server_get_type_addr(const struct domain *d,
> +                                     const ioreq_t *p,
> +                                     uint8_t *type,
> +                                     uint64_t *addr)
> +{
> +    if ( p->type != IOREQ_TYPE_COPY && p->type != IOREQ_TYPE_PIO )
> +        return false;
> +
> +    *type = (p->type == IOREQ_TYPE_PIO) ?
> +             XEN_DMOP_IO_RANGE_PORT : XEN_DMOP_IO_RANGE_MEMORY;
> +    *addr = p->addr;
> +
> +    return true;
> +}
> +
> +void arch_ioreq_domain_init(struct domain *d)
> +{
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * tab-width: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 22bd1bd..036b13f 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -21,6 +21,7 @@
>  #include <xen/hypercall.h>
>  #include <xen/init.h>
>  #include <xen/iocap.h>
> +#include <xen/ioreq.h>
>  #include <xen/irq.h>
>  #include <xen/lib.h>
>  #include <xen/mem_access.h>
> @@ -1385,6 +1386,9 @@ static arm_hypercall_t arm_hypercall_table[] = {
>  #ifdef CONFIG_HYPFS
>      HYPERCALL(hypfs_op, 5),
>  #endif
> +#ifdef CONFIG_IOREQ_SERVER
> +    HYPERCALL(dm_op, 3),
> +#endif
>  };
>  
>  #ifndef NDEBUG
> @@ -1956,6 +1960,9 @@ static void do_trap_stage2_abort_guest(struct 
> cpu_user_regs *regs,
>              case IO_HANDLED:
>                  advance_pc(regs, hsr);
>                  return;
> +            case IO_RETRY:
> +                /* finish later */
> +                return;
>              case IO_UNHANDLED:
>                  /* IO unhandled, try another way to handle it. */
>                  break;
> @@ -2254,6 +2261,12 @@ static void check_for_vcpu_work(void)
>  {
>      struct vcpu *v = current;
>  
> +#ifdef CONFIG_IOREQ_SERVER
> +    local_irq_enable();
> +    vcpu_ioreq_handle_completion(v);
> +    local_irq_disable();
> +#endif
> +
>      if ( likely(!v->arch.need_flush_to_ram) )
>          return;
>  
> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> index 6819a3b..c235e5b 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -10,6 +10,7 @@
>  #include <asm/gic.h>
>  #include <asm/vgic.h>
>  #include <asm/vpl011.h>
> +#include <public/hvm/dm_op.h>
>  #include <public/hvm/params.h>
>  
>  struct hvm_domain
> @@ -262,6 +263,8 @@ static inline void arch_vcpu_block(struct vcpu *v) {}
>  
>  #define arch_vm_assist_valid_mask(d) (1UL << 
> VMASST_TYPE_runstate_update_flag)
>  
> +#define has_vpci(d)    ({ (void)(d); false; })
> +
>  #endif /* __ASM_DOMAIN_H__ */
>  
>  /*
> diff --git a/xen/include/asm-arm/hvm/ioreq.h b/xen/include/asm-arm/hvm/ioreq.h
> new file mode 100644
> index 0000000..19e1247
> --- /dev/null
> +++ b/xen/include/asm-arm/hvm/ioreq.h
> @@ -0,0 +1,72 @@
> +/*
> + * hvm.h: Hardware virtual machine assist interface definitions.
> + *
> + * Copyright (c) 2016 Citrix Systems Inc.
> + * Copyright (c) 2019 Arm ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along 
> with
> + * this program; If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef __ASM_ARM_HVM_IOREQ_H__
> +#define __ASM_ARM_HVM_IOREQ_H__
> +
> +#ifdef CONFIG_IOREQ_SERVER
> +enum io_state handle_ioserv(struct cpu_user_regs *regs, struct vcpu *v);
> +enum io_state try_fwd_ioserv(struct cpu_user_regs *regs,
> +                             struct vcpu *v, mmio_info_t *info);
> +#else
> +static inline enum io_state handle_ioserv(struct cpu_user_regs *regs,
> +                                          struct vcpu *v)
> +{
> +    return IO_UNHANDLED;
> +}
> +
> +static inline enum io_state try_fwd_ioserv(struct cpu_user_regs *regs,
> +                                           struct vcpu *v, mmio_info_t *info)
> +{
> +    return IO_UNHANDLED;
> +}
> +#endif
> +
> +bool ioreq_complete_mmio(void);
> +
> +static inline bool handle_pio(uint16_t port, unsigned int size, int dir)
> +{
> +    /*
> +     * TODO: For Arm64, the main user will be PCI. So this should be
> +     * implemented when we add support for vPCI.
> +     */
> +    ASSERT_UNREACHABLE();
> +    return true;
> +}
> +
> +static inline void msix_write_completion(struct vcpu *v)
> +{
> +}
> +
> +/* This correlation must not be altered */
> +#define IOREQ_STATUS_HANDLED     IO_HANDLED
> +#define IOREQ_STATUS_UNHANDLED   IO_UNHANDLED
> +#define IOREQ_STATUS_RETRY       IO_RETRY
> +
> +#endif /* __ASM_ARM_HVM_IOREQ_H__ */
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * tab-width: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/include/asm-arm/mmio.h b/xen/include/asm-arm/mmio.h
> index 8dbfb27..7ab873c 100644
> --- a/xen/include/asm-arm/mmio.h
> +++ b/xen/include/asm-arm/mmio.h
> @@ -37,6 +37,7 @@ enum io_state
>      IO_ABORT,       /* The IO was handled by the helper and led to an abort. 
> */
>      IO_HANDLED,     /* The IO was successfully handled by the helper. */
>      IO_UNHANDLED,   /* The IO was not handled by the helper. */
> +    IO_RETRY,       /* Retry the emulation for some reason */
>  };
>  
>  typedef int (*mmio_read_t)(struct vcpu *v, mmio_info_t *info,
> -- 
> 2.7.4
>