Re: [PATCH v1 1/2] util: Add functions for s390x mmio read/write

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Mar 26, 2025 at 11:10:06AM -0700, Farhan Ali wrote:
> Starting with z15 (or newer) we can execute mmio
> instructions from userspace. On older platforms
> where we don't have these instructions available
> we can fallback to using system calls to access
> the PCI mapped resources.
> 
> This patch adds helper functions for mmio reads
> and writes for s390x.
> 
> Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
> ---
>  include/qemu/s390x_pci_mmio.h |  17 ++++++
>  util/meson.build              |   2 +
>  util/s390x_pci_mmio.c         | 105 ++++++++++++++++++++++++++++++++++
>  3 files changed, 124 insertions(+)
>  create mode 100644 include/qemu/s390x_pci_mmio.h
>  create mode 100644 util/s390x_pci_mmio.c
> 
> diff --git a/include/qemu/s390x_pci_mmio.h b/include/qemu/s390x_pci_mmio.h
> new file mode 100644
> index 0000000000..be61b5ae29
> --- /dev/null
> +++ b/include/qemu/s390x_pci_mmio.h
> @@ -0,0 +1,17 @@
> +/*
> + * s390x PCI MMIO definitions
> + *
> + * Copyright 2025 IBM Corp.
> + * Author(s): Farhan Ali <alifm@linux.ibm.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +#ifndef S390X_PCI_MMIO_H
> +#define S390X_PCI_MMIO_H
> +
> +uint64_t s390x_pci_mmio_read_64(const void *ioaddr);
> +uint32_t s390x_pci_mmio_read_32(const void *ioaddr);
> +void s390x_pci_mmio_write_64(void *ioaddr, uint64_t val);
> +void s390x_pci_mmio_write_32(void *ioaddr, uint32_t val);
> +
> +#endif
> diff --git a/util/meson.build b/util/meson.build
> index 780b5977a8..acb21592f9 100644
> --- a/util/meson.build
> +++ b/util/meson.build
> @@ -131,4 +131,6 @@ elif cpu in ['ppc', 'ppc64']
>    util_ss.add(files('cpuinfo-ppc.c'))
>  elif cpu in ['riscv32', 'riscv64']
>    util_ss.add(files('cpuinfo-riscv.c'))
> +elif cpu == 's390x'
> +  util_ss.add(files('s390x_pci_mmio.c'))
>  endif
> diff --git a/util/s390x_pci_mmio.c b/util/s390x_pci_mmio.c
> new file mode 100644
> index 0000000000..2e0825d617
> --- /dev/null
> +++ b/util/s390x_pci_mmio.c
> @@ -0,0 +1,105 @@
> +/*
> + * s390x PCI MMIO definitions
> + *
> + * Copyright 2025 IBM Corp.
> + * Author(s): Farhan Ali <alifm@linux.ibm.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include <unistd.h>
> +#include <sys/syscall.h>
> +#include "qemu/osdep.h"

This should be the first #include in the file. From
docs/devel/style.rst:

  Include directives
  ------------------
  
  Order include directives as follows:
  
  .. code-block:: c
  
      #include "qemu/osdep.h"  /* Always first... */
      #include <...>           /* then system headers... */
      #include "..."           /* and finally QEMU headers. */

Otherwise:

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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