On Tue, May 25, 2021 at 06:59:31AM +0000, Dov Murik wrote:
> From: James Bottomley <j...@linux.ibm.com>
>
> If the VM is using memory encryption and also specifies a kernel/initrd
> or appended command line, calculate the hashes and add them to the
> encrypted data. For this to work, OVMF must support an encrypted area
> to place the data which is advertised via a special GUID in the OVMF
> reset table (if the GUID doesn't exist, the user isn't allowed to pass
> in the kernel/initrd/cmdline via the fw_cfg interface).
>
> The hashes of each of the files is calculated (or the string in the case
> of the cmdline with trailing '\0' included). Each entry in the hashes
> table is GUID identified and since they're passed through the memcrypt
> interface, the hash of the encrypted data will be accumulated by the
> PSP.
>
> Signed-off-by: James Bottomley <j...@linux.ibm.com>
> Signed-off-by: Dov Murik <dovmu...@linux.ibm.com>
> [dovmu...@linux.ibm.com: use machine->cgs, remove parsing of GUID
> strings, remove GCC pragma, fix checkpatch errors]
> ---
>
> OVMF support for handling the table of hashes (verifying that the
> kernel/initrd/cmdline passed via the fw_cfg interface indeed correspond
> to the measured hashes in the table) will be posted soon to edk2-devel.
>
> ---
> hw/i386/x86.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 119 insertions(+), 1 deletion(-)
>
This is not an objection to the patch itself, but: can we do
something to move all sev-related code to sev.c? It would make
the process of assigning a maintainer and reviewing/merging
future patches much simpler.
I am not familiar with SEV internals, so my only question is
about configurations where SEV is disabled:
[...]
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> @@ -778,6 +818,11 @@ void x86_load_linux(X86MachineState *x86ms,
> const char *initrd_filename = machine->initrd_filename;
> const char *dtb_filename = machine->dtb;
> const char *kernel_cmdline = machine->kernel_cmdline;
> + uint8_t buf[HASH_SIZE];
> + uint8_t *hash = buf;
> + size_t hash_len = sizeof(buf);
> + struct sev_hash_table *sev_ht = NULL;
> + int sev_ht_index = 0;
>
> /* Align to 16 bytes as a paranoia measure */
> cmdline_size = (strlen(kernel_cmdline) + 16) & ~15;
> @@ -799,6 +844,22 @@ void x86_load_linux(X86MachineState *x86ms,
> exit(1);
> }
>
> + if (machine->cgs && machine->cgs->ready) {
machine->cgs doesn't seem to be a SEV-specific field.
What if machine->cgs->ready is set but SEV is disabled?
> + uint8_t *data;
> + struct sev_hash_table_descriptor *area;
> +
> + if (!pc_system_ovmf_table_find(SEV_HASH_TABLE_RV_GUID, &data, NULL))
> {
> + fprintf(stderr, "qemu: kernel command line specified but OVMF
> has "
> + "no hash table guid\n");
> + exit(1);
> + }
> + area = (struct sev_hash_table_descriptor *)data;
> +
> + sev_ht = qemu_map_ram_ptr(NULL, area->base);
> + memcpy(sev_ht->guid, sev_hash_table_header_guid,
> sizeof(sev_ht->guid));
> + sev_ht->len = sizeof(*sev_ht);
> + }
> +
> /* kernel protocol version */
> if (ldl_p(header + 0x202) == 0x53726448) {
> protocol = lduw_p(header + 0x206);
[...]
--
Eduardo
