[Skiboot] [PATCH v8 05/11] xscoms: read/write xscoms using ucall

[Oliver O'Halloran]

On Thu, Aug 27, 2020 at 4:41 AM Ryan Grimm <grimm at linux.ibm.com> wrote:
>
> From: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>
>
> xscom registers are in the secure memory area when secure mode is
> enabled. These registers cannot be accessed directly and need to use
> ultravisor services using ultracall.
>
> Signed-off-by: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>
> Signed-off-by: Santosh Sivaraj <santosh at fossix.org>
> [ linuxram: Set uv_present just after starting UV ]
> Signed-off-by: Ram Pai <linuxram at us.ibm.com>
> [ grimm: Don't check MSR in xscom read/write ]
> Signed-off-by: Ryan Grimm <grimm at linux.ibm.com>
> ---
>  include/ultravisor.h | 21 +++++++++++++++++++++
>  include/xscom.h      |  5 +++++
>  2 files changed, 26 insertions(+)
>
> diff --git a/include/ultravisor.h b/include/ultravisor.h
> index 623b81d4..84217d66 100644
> --- a/include/ultravisor.h
> +++ b/include/ultravisor.h
> @@ -7,6 +7,7 @@
>  #include <stdbool.h>
>  #include <stdint.h>
>  #include <types.h>
> +#include <processor.h>
>
>  /*
>   * enter_uv: Each thread enters ultravisor and exits with S=0
> @@ -43,4 +44,24 @@ void init_uv(void);
>  #define UCALL_BUFSIZE 4
>  extern long ucall(unsigned long opcode, unsigned long *retbuf, ...);
>
> +#define UV_READ_SCOM  0xF114
> +#define UV_WRITE_SCOM 0xF118
> +
> +static inline int uv_xscom_read(u64 partid, u64 pcb_addr, u64 *val)
> +{
> +       unsigned long retbuf[UCALL_BUFSIZE];
> +       long rc;
> +
> +       rc = ucall(UV_READ_SCOM, retbuf, partid, pcb_addr);
> +       *val = retbuf[0];
> +       return rc;
> +}
> +
> +static inline int uv_xscom_write(u64 partid, u64 pcb_addr, u64 val)
> +{
> +       unsigned long retbuf[UCALL_BUFSIZE];
> +
> +       return ucall(UV_WRITE_SCOM, retbuf, partid, pcb_addr, val);
> +}
> +
>  #endif /* __ULTRAVISOR_H */
> diff --git a/include/xscom.h b/include/xscom.h
> index bd8bb89a..67a845fd 100644
> --- a/include/xscom.h
> +++ b/include/xscom.h
> @@ -7,6 +7,7 @@
>  #include <stdint.h>
>  #include <processor.h>
>  #include <cpu.h>
> +#include <ultravisor.h>
>
>  /*
>   * SCOM "partID" definitions:
> @@ -174,9 +175,13 @@ extern void _xscom_unlock(void);
>  /* Targeted SCOM access */
>  static inline int xscom_read(uint32_t partid, uint64_t pcb_addr, uint64_t *val)
>  {
> +       if (uv_present)
> +               return uv_xscom_read(partid, pcb_addr, val);
>         return _xscom_read(partid, pcb_addr, val, true);
>  }
>  static inline int xscom_write(uint32_t partid, uint64_t pcb_addr, uint64_t val) {
> +       if (uv_present)
> +               return uv_xscom_write(partid, pcb_addr, val);
>         return _xscom_write(partid, pcb_addr, val, true);
>  }

This should probably go into __xscom_write() since it'll break
emulated scoms that we use for the OCMBs addresses on swift and P10.
The UV would also need to support that, but I have some patches to use
the xscom API to access other register spaces (e.g. PHB IODA tables)
which this would also break.

>  extern int xscom_write_mask(uint32_t partid, uint64_t pcb_addr, uint64_t val, uint64_t mask);
> --
> 2.18.4
>
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