Re: [PATCH v2] target/s390x/kvm/pv: Provide some more useful information if decryption fails

["Cédric Le Goater" <clegoate@redhat.com>]

On 1/10/24 15:29, Thomas Huth wrote:
> It's a common scenario to copy guest images from one host to another
> to run the guest on the other machine. This (of course) does not work
> with "secure exection" guests since they are encrypted with one certain
> host key. However, if you still (accidentally) do it, you only get a
> very user-unfriendly error message that looks like this:
> 
>   qemu-system-s390x: KVM PV command 2 (KVM_PV_SET_SEC_PARMS) failed:
>    header rc 108 rrc 5 IOCTL rc: -22
> 
> Let's provide at least a somewhat nicer hint to the users so that they
> are able to figure out what might have gone wrong.
> 
> Buglink: https://issues.redhat.com/browse/RHEL-18212
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   v2: Print the error in s390_machine_protect() instead of doing it
>       in s390_pv_set_sec_parms(), report the text via Error **errp


Reviewed-by: Cédric Le Goater <clg@redhat.com>

s390_pv_query_info(), s390_ipl_pv_unpack() and s390_pv_verify() are
good candidates for similar changes. Anyhow, it can come later.

Thanks,

C.


>   hw/s390x/ipl.h             |  2 +-
>   target/s390x/kvm/pv.h      |  2 +-
>   hw/s390x/ipl.c             |  5 ++---
>   hw/s390x/s390-virtio-ccw.c |  5 ++++-
>   target/s390x/kvm/pv.c      | 25 ++++++++++++++++++++-----
>   5 files changed, 28 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/s390x/ipl.h b/hw/s390x/ipl.h
> index 7fc86e7905..57cd125769 100644
> --- a/hw/s390x/ipl.h
> +++ b/hw/s390x/ipl.h
> @@ -107,7 +107,7 @@ typedef union IplParameterBlock IplParameterBlock;
>   
>   int s390_ipl_set_loadparm(uint8_t *loadparm);
>   void s390_ipl_update_diag308(IplParameterBlock *iplb);
> -int s390_ipl_prepare_pv_header(void);
> +int s390_ipl_prepare_pv_header(Error **errp);
>   int s390_ipl_pv_unpack(void);
>   void s390_ipl_prepare_cpu(S390CPU *cpu);
>   IplParameterBlock *s390_ipl_get_iplb(void);
> diff --git a/target/s390x/kvm/pv.h b/target/s390x/kvm/pv.h
> index 7b935e2246..fca373a826 100644
> --- a/target/s390x/kvm/pv.h
> +++ b/target/s390x/kvm/pv.h
> @@ -42,7 +42,7 @@ int s390_pv_query_info(void);
>   int s390_pv_vm_enable(void);
>   void s390_pv_vm_disable(void);
>   bool s390_pv_vm_try_disable_async(S390CcwMachineState *ms);
> -int s390_pv_set_sec_parms(uint64_t origin, uint64_t length);
> +int s390_pv_set_sec_parms(uint64_t origin, uint64_t length, Error **errp);
>   int s390_pv_unpack(uint64_t addr, uint64_t size, uint64_t tweak);
>   void s390_pv_prep_reset(void);
>   int s390_pv_verify(void);
> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
> index 76110e8f58..e934bf89d1 100644
> --- a/hw/s390x/ipl.c
> +++ b/hw/s390x/ipl.c
> @@ -702,7 +702,7 @@ static void s390_ipl_prepare_qipl(S390CPU *cpu)
>       cpu_physical_memory_unmap(addr, len, 1, len);
>   }
>   
> -int s390_ipl_prepare_pv_header(void)
> +int s390_ipl_prepare_pv_header(Error **errp)
>   {
>       IplParameterBlock *ipib = s390_ipl_get_iplb_pv();
>       IPLBlockPV *ipib_pv = &ipib->pv;
> @@ -711,8 +711,7 @@ int s390_ipl_prepare_pv_header(void)
>   
>       cpu_physical_memory_read(ipib_pv->pv_header_addr, hdr,
>                                ipib_pv->pv_header_len);
> -    rc = s390_pv_set_sec_parms((uintptr_t)hdr,
> -                               ipib_pv->pv_header_len);
> +    rc = s390_pv_set_sec_parms((uintptr_t)hdr, ipib_pv->pv_header_len, errp);
>       g_free(hdr);
>       return rc;
>   }
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 1169e20b94..eaf61d3640 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -391,7 +391,7 @@ static int s390_machine_protect(S390CcwMachineState *ms)
>       }
>   
>       /* Set SE header and unpack */
> -    rc = s390_ipl_prepare_pv_header();
> +    rc = s390_ipl_prepare_pv_header(&local_err);
>       if (rc) {
>           goto out_err;
>       }
> @@ -410,6 +410,9 @@ static int s390_machine_protect(S390CcwMachineState *ms)
>       return rc;
>   
>   out_err:
> +    if (local_err) {
> +        error_report_err(local_err);
> +    }
>       s390_machine_unprotect(ms);
>       return rc;
>   }
> diff --git a/target/s390x/kvm/pv.c b/target/s390x/kvm/pv.c
> index 6a69be7e5c..7ca7faec73 100644
> --- a/target/s390x/kvm/pv.c
> +++ b/target/s390x/kvm/pv.c
> @@ -29,7 +29,8 @@ static bool info_valid;
>   static struct kvm_s390_pv_info_vm info_vm;
>   static struct kvm_s390_pv_info_dump info_dump;
>   
> -static int __s390_pv_cmd(uint32_t cmd, const char *cmdname, void *data)
> +static int __s390_pv_cmd(uint32_t cmd, const char *cmdname, void *data,
> +                         int *pvrc)
>   {
>       struct kvm_pv_cmd pv_cmd = {
>           .cmd = cmd,
> @@ -46,6 +47,9 @@ static int __s390_pv_cmd(uint32_t cmd, const char *cmdname, void *data)
>                        "IOCTL rc: %d", cmd, cmdname, pv_cmd.rc, pv_cmd.rrc,
>                        rc);
>       }
> +    if (pvrc) {
> +        *pvrc = pv_cmd.rc;
> +    }
>       return rc;
>   }
>   
> @@ -53,12 +57,13 @@ static int __s390_pv_cmd(uint32_t cmd, const char *cmdname, void *data)
>    * This macro lets us pass the command as a string to the function so
>    * we can print it on an error.
>    */
> -#define s390_pv_cmd(cmd, data) __s390_pv_cmd(cmd, #cmd, data)
> +#define s390_pv_cmd(cmd, data) __s390_pv_cmd(cmd, #cmd, data, NULL)
> +#define s390_pv_cmd_pvrc(cmd, data, pvrc) __s390_pv_cmd(cmd, #cmd, data, pvrc)
>   #define s390_pv_cmd_exit(cmd, data)    \
>   {                                      \
>       int rc;                            \
>                                          \
> -    rc = __s390_pv_cmd(cmd, #cmd, data);\
> +    rc = __s390_pv_cmd(cmd, #cmd, data, NULL); \
>       if (rc) {                          \
>           exit(1);                       \
>       }                                  \
> @@ -142,14 +147,24 @@ bool s390_pv_vm_try_disable_async(S390CcwMachineState *ms)
>       return true;
>   }
>   
> -int s390_pv_set_sec_parms(uint64_t origin, uint64_t length)
> +int s390_pv_set_sec_parms(uint64_t origin, uint64_t length, Error **errp)
>   {
> +    int ret, pvrc;
>       struct kvm_s390_pv_sec_parm args = {
>           .origin = origin,
>           .length = length,
>       };
>   
> -    return s390_pv_cmd(KVM_PV_SET_SEC_PARMS, &args);
> +    ret = s390_pv_cmd_pvrc(KVM_PV_SET_SEC_PARMS, &args, &pvrc);
> +    if (ret) {
> +        error_setg(errp, "Failed to set secure execution parameters");
> +        if (pvrc == 0x108) {
> +            error_append_hint(errp, "Please check whether the image is "
> +                                    "correctly encrypted for this host\n");
> +        }
> +    }
> +
> +    return ret;
>   }
>   
>   /*