On 14/09/2016 04:28, Michael S. Tsirkin wrote: > On Tue, Sep 13, 2016 at 10:48:27AM -0400, Brijesh Singh wrote: >> The SEV DEBUG_DECRYPT command is used for decrypting a guest memory >> for the debugging purposes. Note that debugging is permitting only >> when guest policy allows it. > > When wouldn't you want to allow it? > I don't see value in a "break debugging" feature.
One man's "allow debugging" feature is another man's "break encryption" feature. :) Paolo > >> For more information see [1], section 7.1 >> >> [1] http://support.amd.com/TechDocs/55766_SEV-KM%20API_Spec.pdf > > Please add comments documenting APIs. Spec links to figure out > implementation is one thing, but you really can't require people > to read specs just to figure out how to use an API. > >> The following KVM RFC patches defines and implements this command >> >> http://marc.info/?l=kvm&m=147190852423972&w=2 >> http://marc.info/?l=kvm&m=147191068524579&w=2 >> >> Signed-off-by: Brijesh Singh <[email protected]> >> --- >> include/sysemu/sev.h | 10 ++++++++++ >> sev.c | 23 +++++++++++++++++++++++ >> 2 files changed, 33 insertions(+) >> >> diff --git a/include/sysemu/sev.h b/include/sysemu/sev.h >> index ab03c5d..5872c3e 100644 >> --- a/include/sysemu/sev.h >> +++ b/include/sysemu/sev.h >> @@ -55,4 +55,14 @@ int kvm_sev_guest_finish(void); >> */ >> int kvm_sev_guest_measurement(uint8_t *measurement); >> >> +/** >> + * kvm_sev_dbg_decrypt - decrypt the guest memory for debugging purposes >> + * @src - guest memory address >> + * @dest - host memory address where the decrypted data should be copied >> + * @length - length of memory region >> + * >> + * Returns: 0 on success and dest will contains the decrypted data >> + */ >> +int kvm_sev_dbg_decrypt(uint8_t *dest, const uint8_t *src, uint32_t len); >> + >> #endif >> diff --git a/sev.c b/sev.c >> index 055ed83..c7031d3 100644 >> --- a/sev.c >> +++ b/sev.c >> @@ -432,3 +432,26 @@ int kvm_sev_guest_measurement(uint8_t *out) >> >> return 0; >> } >> + >> +int kvm_sev_dbg_decrypt(uint8_t *dst, const uint8_t *src, uint32_t len) >> +{ >> + int ret; >> + struct kvm_sev_dbg_decrypt decrypt; >> + struct kvm_sev_issue_cmd input; >> + >> + decrypt.src_addr = (unsigned long)src; >> + decrypt.dst_addr = (unsigned long)dst; >> + decrypt.length = len; >> + >> + input.cmd = KVM_SEV_DBG_DECRYPT; >> + input.opaque = (unsigned long)&decrypt; >> + ret = kvm_vm_ioctl(kvm_state, KVM_SEV_ISSUE_CMD, &input); >> + if (ret) { >> + fprintf(stderr, "SEV: dbg_decrypt failed ret=%d(%#010x)\n", >> + ret, input.ret_code); >> + return 1; >> + } >> + >> + DPRINTF("SEV: DBG_DECRYPT dst %p src %p sz %d\n", dst, src, len); >> + return 0; >> +} > >
