* Brijesh Singh (brijesh.singh@xxxxxxx) wrote:
>
>
> On 03/07/2018 11:27 AM, Dr. David Alan Gilbert wrote:
>
> [...]
>
> > > +{
> > > + SEVState *s = (SEVState *)handle;
> > > +
> > > + /* If policy does not allow debug then no need to register ops */
> > > + if (s->policy & SEV_POLICY_NODBG) {
> > > + return;
> > > + }
> >
> > So what happens if someone tries to use a gdb or monitor command when
> > policy didn't allow debug? Does it end up with an obvious error
> > somehow?
> >
>
> In those cases caller will get encrypted bytes, leading to unintelligible
> data. It can sometime translate into obvious errors e.g caller tries to
> walk guest pagtable and it gets garbage and will have trouble dumping the
> pgtables etc. Many times qemu calls ldphys_* functions to access the data it
> may get tricky to report the errors.
So would it make sense to have something like:
sev_mem_cant_read(uint8_t *dst, const uint8_t *src, uint32_t len, MemTxAttrs attrs)
{
error_report("SEV Guest policy does not allow debug access");
return -EPERM;
}
void
sev_set_debug_ops(void *handle, MemoryRegion *mr)
{
SEVState *s = (SEVState *)handle;
/* If policy does not allow debug then no need to register ops */
if (s->policy & SEV_POLICY_NODBG) {
sev_ops.read = sev_mem_cant_read;
sev_ops.write = sev_mem_cant_write;
} else {
sev_ops.read = sev_mem_read;
sev_ops.write = sev_mem_write;
}
Dave
>
> -Brijesh
--
Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
