Re: [PATCH v2 47/58] i386/tdx: Wire REPORT_FATAL_ERROR with GuestPanic facility

[Daniel P . Berrangé]

On Mon, Aug 28, 2023 at 09:14:41PM +0800, Xiaoyao Li wrote:
> On 8/21/2023 5:58 PM, Daniel P. Berrangé wrote:
> > On Fri, Aug 18, 2023 at 05:50:30AM -0400, Xiaoyao Li wrote:
> > > Originated-from: Isaku Yamahata <isaku.yamahata@intel.com>
> > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > > ---
> > >   qapi/run-state.json   | 17 +++++++++++++--
> > >   softmmu/runstate.c    | 49 +++++++++++++++++++++++++++++++++++++++++++
> > >   target/i386/kvm/tdx.c | 24 ++++++++++++++++++++-
> > >   3 files changed, 87 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/qapi/run-state.json b/qapi/run-state.json
> > > index f216ba54ec4c..506bbe31541f 100644
> > > --- a/qapi/run-state.json
> > > +++ b/qapi/run-state.json
> > > @@ -499,7 +499,7 @@
> > >   # Since: 2.9
> > >   ##
> > >   { 'enum': 'GuestPanicInformationType',
> > > -  'data': [ 'hyper-v', 's390' ] }
> > > +  'data': [ 'hyper-v', 's390', 'tdx' ] }

> 
> > > +#
> > > +# Since: 8.2
> > > +##
> > > +{'struct': 'GuestPanicInformationTdx',
> > > + 'data': {'error-code': 'uint64',
> > > +          'gpa': 'uint64',
> > > +          'message': 'str'}}
> > > +
> > >   ##
> > >   # @MEMORY_FAILURE:
> > >   #
> > > diff --git a/softmmu/runstate.c b/softmmu/runstate.c
> > > index f3bd86281813..cab11484ed7e 100644
> > > --- a/softmmu/runstate.c
> > > +++ b/softmmu/runstate.c
> > > @@ -518,7 +518,56 @@ void 
> > > qemu_system_guest_panicked(GuestPanicInformation *info)
> > >                             S390CrashReason_str(info->u.s390.reason),
> > >                             info->u.s390.psw_mask,
> > >                             info->u.s390.psw_addr);
> > > +        } else if (info->type == GUEST_PANIC_INFORMATION_TYPE_TDX) {
> > > +            char *buf = NULL;
> > > +            bool printable = false;
> > > +
> > > +            /*
> > > +             * Although message is defined as a json string, we shouldn't
> > > +             * unconditionally treat it as is because the guest 
> > > generated it and
> > > +             * it's not necessarily trustable.
> > > +             */
> > > +            if (info->u.tdx.message) {
> > > +                /* The caller guarantees the NUL-terminated string. */
> > > +                int len = strlen(info->u.tdx.message);
> > > +                int i;
> > > +
> > > +                printable = len > 0;
> > > +                for (i = 0; i < len; i++) {
> > > +                    if (!(0x20 <= info->u.tdx.message[i] &&
> > > +                          info->u.tdx.message[i] <= 0x7e)) {
> > > +                        printable = false;
> > > +                        break;
> > > +                    }
> > > +                }
> > > +
> > > +                /* 3 = length of "%02x " */
> > > +                buf = g_malloc(len * 3);
> > > +                for (i = 0; i < len; i++) {
> > > +                    if (info->u.tdx.message[i] == '\0') {
> > > +                        break;
> > > +                    } else {
> > > +                        sprintf(buf + 3 * i, "%02x ", 
> > > info->u.tdx.message[i]);
> > > +                    }
> > > +                }
> > > +                if (i > 0)
> > > +                    /* replace the last ' '(space) to NUL */
> > > +                    buf[i * 3 - 1] = '\0';
> > > +                else
> > > +                    buf[0] = '\0';
> > 
> > You're building this escaped buffer but...
> > 
> > > +            }
> > > +
> > > +            qemu_log_mask(LOG_GUEST_ERROR,
> > > +                          //" TDX report fatal error:\"%s\" %s",
> > > +                          " TDX report fatal error:\"%s\""
> > > +                          "error: 0x%016" PRIx64 " gpa page: 0x%016" 
> > > PRIx64 "\n",
> > > +                          printable ? info->u.tdx.message : "",
> > > +                          //buf ? buf : "",
> > 
> > ...then not actually using it
> > 
> > Either delete the 'buf' code, or use it.
> 
> Sorry for posting some internal testing version.
> Does below look good to you?
> 
> @@ -518,7 +518,56 @@ void qemu_system_guest_panicked(GuestPanicInformation
> *info)
>                            S390CrashReason_str(info->u.s390.reason),
>                            info->u.s390.psw_mask,
>                            info->u.s390.psw_addr);
> +        } else if (info->type == GUEST_PANIC_INFORMATION_TYPE_TDX) {
> +            bool printable = false;
> +            char *buf = NULL;
> +            int len = 0, i;
> +
> +            /*
> +             * Although message is defined as a json string, we shouldn't
> +             * unconditionally treat it as is because the guest generated
> it and
> +             * it's not necessarily trustable.
> +             */
> +            if (info->u.tdx.message) {
> +                /* The caller guarantees the NUL-terminated string. */
> +                len = strlen(info->u.tdx.message);
> +
> +                printable = len > 0;
> +                for (i = 0; i < len; i++) {
> +                    if (!(0x20 <= info->u.tdx.message[i] &&
> +                          info->u.tdx.message[i] <= 0x7e)) {
> +                        printable = false;
> +                        break;
> +                    }
> +                }
> +            }
> +
> +            if (!printable && len) {
> +                /* 3 = length of "%02x " */
> +                buf = g_malloc(len * 3);
> +                for (i = 0; i < len; i++) {
> +                    if (info->u.tdx.message[i] == '\0') {
> +                        break;
> +                    } else {
> +                        sprintf(buf + 3 * i, "%02x ",
> info->u.tdx.message[i]);
> +                    }
> +                }
> +                if (i > 0)
> +                    /* replace the last ' '(space) to NUL */
> +                    buf[i * 3 - 1] = '\0';
> +                else
> +                    buf[0] = '\0';
> +            }
> +
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          " TDX guest reports fatal error:\"%s\""
> +                          " error code: 0x%016" PRIx64 " gpa page: 0x%016"
> PRIx64 "\n",
> +                          printable ? info->u.tdx.message : buf,
> +                          info->u.tdx.error_code,
> +                          info->u.tdx.gpa);
> +            g_free(buf);
>          }


Ok that makes more sense now. BTW, probably a nice idea to create a
separate helper method that santizes the guest provided JSON into
the safe 'buf' string.


With regards,
Daniel
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