Re: [PATCH 3/4] target/ppc: Fix kvmppc_load_htab_chunk() error reporting

[David Gibson]

On Mon, Oct 26, 2020 at 01:40:47PM +0100, Greg Kurz wrote:
> If kvmppc_load_htab_chunk() fails, its return value is propagated up
> to vmstate_load(). It should thus be a negative errno, not -1 (which
> maps to EPERM and would lure the user into thinking that the problem
> is necessarily related to a lack of privilege).
> 
> Return the error reported by KVM or ENOSPC in case of short write.
> While here, propagate the error message through an @errp argument
> and have the caller to print it with error_report_err() instead
> of relying on fprintf().
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
>  hw/ppc/spapr.c       |    4 +++-
>  target/ppc/kvm.c     |   11 +++++------
>  target/ppc/kvm_ppc.h |    5 +++--
>  3 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index f51b663f7dcb..ff7de7da2875 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2341,8 +2341,10 @@ static int htab_load(QEMUFile *f, void *opaque, int 
> version_id)
>  
>              assert(fd >= 0);
>  
> -            rc = kvmppc_load_htab_chunk(f, fd, index, n_valid, n_invalid);
> +            rc = kvmppc_load_htab_chunk(f, fd, index, n_valid, n_invalid,
> +                                        &local_err);
>              if (rc < 0) {
> +                error_report_err(local_err);
>                  return rc;
>              }
>          }
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index d85ba8ffe00b..0223b93ea561 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -2683,7 +2683,7 @@ int kvmppc_save_htab(QEMUFile *f, int fd, size_t 
> bufsize, int64_t max_ns)
>  }
>  
>  int kvmppc_load_htab_chunk(QEMUFile *f, int fd, uint32_t index,
> -                           uint16_t n_valid, uint16_t n_invalid)
> +                           uint16_t n_valid, uint16_t n_invalid, Error 
> **errp)
>  {
>      struct kvm_get_htab_header *buf;
>      size_t chunksize = sizeof(*buf) + n_valid * HASH_PTE_SIZE_64;
> @@ -2698,14 +2698,13 @@ int kvmppc_load_htab_chunk(QEMUFile *f, int fd, 
> uint32_t index,
>  
>      rc = write(fd, buf, chunksize);
>      if (rc < 0) {
> -        fprintf(stderr, "Error writing KVM hash table: %s\n",
> -                strerror(errno));
> -        return rc;
> +        error_setg_errno(errp, errno, "Error writing the KVM hash table");
> +        return -errno;
>      }
>      if (rc != chunksize) {
>          /* We should never get a short write on a single chunk */
> -        fprintf(stderr, "Short write, restoring KVM hash table\n");
> -        return -1;
> +        error_setg(errp, "Short write while restoring the KVM hash table");
> +        return -ENOSPC;

I'm not entirely sure -ENOSPC is the right choice here - this
indicates that the kernel interface is not behaving as we expect.  But
I can't immediately think of what's a better choice, so, applied to
ppc-for-5.2.


>      }
>      return 0;
>  }
> diff --git a/target/ppc/kvm_ppc.h b/target/ppc/kvm_ppc.h
> index 72e05f1cd2fc..73ce2bc95114 100644
> --- a/target/ppc/kvm_ppc.h
> +++ b/target/ppc/kvm_ppc.h
> @@ -56,7 +56,7 @@ int kvmppc_define_rtas_kernel_token(uint32_t token, const 
> char *function);
>  int kvmppc_get_htab_fd(bool write, uint64_t index, Error **errp);
>  int kvmppc_save_htab(QEMUFile *f, int fd, size_t bufsize, int64_t max_ns);
>  int kvmppc_load_htab_chunk(QEMUFile *f, int fd, uint32_t index,
> -                           uint16_t n_valid, uint16_t n_invalid);
> +                           uint16_t n_valid, uint16_t n_invalid, Error 
> **errp);
>  void kvmppc_read_hptes(ppc_hash_pte64_t *hptes, hwaddr ptex, int n);
>  void kvmppc_write_hpte(hwaddr ptex, uint64_t pte0, uint64_t pte1);
>  bool kvmppc_has_cap_fixup_hcalls(void);
> @@ -316,7 +316,8 @@ static inline int kvmppc_save_htab(QEMUFile *f, int fd, 
> size_t bufsize,
>  }
>  
>  static inline int kvmppc_load_htab_chunk(QEMUFile *f, int fd, uint32_t index,
> -                                         uint16_t n_valid, uint16_t 
> n_invalid)
> +                                         uint16_t n_valid, uint16_t 
> n_invalid,
> +                                         Error **errp)
>  {
>      abort();
>  }
> 
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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