Re: [RFC v4 10/24] target/arm/kvm-rme: Keep track of images loaded in Realm memory

[Gavin Shan <gshan@redhat.com>]

On 9/4/26 5:35 AM, Mathieu Poirier wrote:
> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
> 
> Add a Rom notifier to keep track of binary blobs loaded in Realm memory.
> That way we can deterministically calculate the Realm Initial Measurement (RIM).
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@linaro.org>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
>   target/arm/kvm-rme.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 52 insertions(+)
> 
> diff --git a/target/arm/kvm-rme.c b/target/arm/kvm-rme.c
> index f7c2cc786e2c..9985f5daba89 100644
> --- a/target/arm/kvm-rme.c
> +++ b/target/arm/kvm-rme.c
> @@ -10,6 +10,7 @@
>   
>   #include "hw/core/boards.h"
>   #include "hw/core/cpu.h"
> +#include "hw/core/loader.h"
>   #include "kvm_arm.h"
>   #include "migration/blocker.h"
>   #include "qapi/error.h"
> @@ -22,8 +23,18 @@
>   #define TYPE_RME_GUEST "rme-guest"
>   OBJECT_DECLARE_SIMPLE_TYPE(RmeGuest, RME_GUEST)
>   
> +#define RME_PAGE_SIZE qemu_real_host_page_size()
> +
> +typedef struct {
> +    hwaddr base;
> +    hwaddr size;
> +    uint8_t *data;
> +} RmeRamRegion;
> +

This is the equivalent to 'RomLoaderNotifyData' defined in PATCH[09/24]. We may
use 'RomLoaderNotifyData' if it can be renamed to reflect its purpose, no need
to define an identical structure.

>   struct RmeGuest {
>       ConfidentialGuestSupport parent_obj;
> +    Notifier rom_load_notifier;
> +    GSList *ram_regions;
>   };
>   
>   OBJECT_DEFINE_SIMPLE_TYPE_WITH_INTERFACES(RmeGuest, rme_guest, RME_GUEST,
> @@ -41,6 +52,44 @@ static void rme_vm_state_change(void *opaque, bool running, RunState state)
>       kvm_mark_guest_state_protected();
>   }
>   
> +static gint rme_compare_ram_regions(gconstpointer a, gconstpointer b)
> +{
> +    const RmeRamRegion *ra = a;
> +    const RmeRamRegion *rb = b;
> +
> +    g_assert(ra->base != rb->base);
> +    return ra->base < rb->base ? -1 : 1;
> +}
> +
> +static void rme_rom_load_notify(Notifier *notifier, void *data)
> +{
> +    RmeRamRegion *region;
> +    RomLoaderNotifyData *rom = data;
> +
> +    if (rom->addr == -1) {
> +        /*
> +         * These blobs (ACPI tables) are not loaded into guest RAM at reset.
> +         * Instead the firmware will load them via fw_cfg and measure them
> +         * itself.
> +         */
> +        return;
> +    }
> +
> +    region = g_new0(RmeRamRegion, 1);
> +    region->base = rom->addr;
> +    region->size = rom->len;
> +    region->data = rom->data;
> +
> +    /*
> +     * The Realm Initial Measurement (RIM) depends on the order in which we
> +     * initialize and populate the RAM regions. To help a verifier
> +     * independently calculate the RIM, sort regions by GPA.
> +     */
> +    rme_guest->ram_regions = g_slist_insert_sorted(rme_guest->ram_regions,
> +                                                   region,
> +                                                   rme_compare_ram_regions);
> +}
> +
>   static int kvm_arm_rme_init(ConfidentialGuestSupport *cgs, Error **errp)
>   {
>       KVMState *s = KVM_STATE(current_accel());
> @@ -58,6 +107,9 @@ static int kvm_arm_rme_init(ConfidentialGuestSupport *cgs, Error **errp)
>       error_setg(&rme_mig_blocker, "RME: migration is not implemented");
>       migrate_add_blocker(&rme_mig_blocker, &error_fatal);
>   
> +    rme_guest->rom_load_notifier.notify = rme_rom_load_notify;
> +    rom_add_load_notifier(&rme_guest->rom_load_notifier);
> +
>       /*
>        * The realm activation is done last, when the VM starts, after all images
>        * have been loaded and all vcpus finalized.

Thanks,
Gavin