Re: [Qemu-devel] [PATCH v5 05/10] ACPI: Add Virtual Machine Generation ID support

[Michael S. Tsirkin]

On Mon, Feb 06, 2017 at 09:29:30AM -0800, Ben Warren wrote:
> 
>     On Feb 6, 2017, at 8:15 AM, Michael S. Tsirkin <address@hidden> wrote:
> 
>     On Sun, Feb 05, 2017 at 01:12:00AM -0800, address@hidden wrote:
> 
>         From: Ben Warren <address@hidden>
> 
>         This implements the VM Generation ID feature by passing a 128-bit
>         GUID to the guest via a fw_cfg blob.
>         Any time the GUID changes, an ACPI notify event is sent to the guest
> 
>         The user interface is a simple device with one parameter:
>         - guid (string, must be "auto" or in UUID format
>           xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx)
> 
>         Signed-off-by: Ben Warren <address@hidden>
> 
> 
> 
>     Thanks!
>     I think it's mostly in a good shape.
>     Comments inside.
> 
> 
> Thanks!  Hopefully the next rev has everything you want.
> 
> 
> 
>         ---
>         default-configs/i386-softmmu.mak     |   1 +
>         default-configs/x86_64-softmmu.mak   |   1 +
>         hw/acpi/Makefile.objs                |   1 +
>         hw/acpi/vmgenid.c                    | 206
>         +++++++++++++++++++++++++++++++++++
>         hw/i386/acpi-build.c                 |  10 ++
>         include/hw/acpi/acpi_dev_interface.h |   1 +
>         include/hw/acpi/vmgenid.h            |  37 +++++++
>         7 files changed, 257 insertions(+)
>         create mode 100644 hw/acpi/vmgenid.c
>         create mode 100644 include/hw/acpi/vmgenid.h
> 
>         diff --git a/default-configs/i386-softmmu.mak b/default-configs/
>         i386-softmmu.mak
>         index 384cefb..1a43542 100644
>         --- a/default-configs/i386-softmmu.mak
>         +++ b/default-configs/i386-softmmu.mak
>         @@ -58,3 +58,4 @@ CONFIG_I82801B11=y
>         CONFIG_SMBIOS=y
>         CONFIG_HYPERV_TESTDEV=$(CONFIG_KVM)
>         CONFIG_PXB=y
>         +CONFIG_ACPI_VMGENID=y
>         diff --git a/default-configs/x86_64-softmmu.mak b/default-configs/
>         x86_64-softmmu.mak
>         index 491a191..aee8b08 100644
>         --- a/default-configs/x86_64-softmmu.mak
>         +++ b/default-configs/x86_64-softmmu.mak
>         @@ -58,3 +58,4 @@ CONFIG_I82801B11=y
>         CONFIG_SMBIOS=y
>         CONFIG_HYPERV_TESTDEV=$(CONFIG_KVM)
>         CONFIG_PXB=y
>         +CONFIG_ACPI_VMGENID=y
>         diff --git a/hw/acpi/Makefile.objs b/hw/acpi/Makefile.objs
>         index 6acf798..11c35bc 100644
>         --- a/hw/acpi/Makefile.objs
>         +++ b/hw/acpi/Makefile.objs
>         @@ -5,6 +5,7 @@ common-obj-$(CONFIG_ACPI_CPU_HOTPLUG) += cpu_hotplug.o
>         common-obj-$(CONFIG_ACPI_MEMORY_HOTPLUG) += memory_hotplug.o
>         common-obj-$(CONFIG_ACPI_CPU_HOTPLUG) += cpu.o
>         common-obj-$(CONFIG_ACPI_NVDIMM) += nvdimm.o
>         +common-obj-$(CONFIG_ACPI_VMGENID) += vmgenid.o
>         common-obj-$(call lnot,$(CONFIG_ACPI_X86)) += acpi-stub.o
> 
>         common-obj-y += acpi_interface.o
>         diff --git a/hw/acpi/vmgenid.c b/hw/acpi/vmgenid.c
>         new file mode 100644
>         index 0000000..6c9ecfd
>         --- /dev/null
>         +++ b/hw/acpi/vmgenid.c
>         @@ -0,0 +1,206 @@
>         +/*
>         + *  Virtual Machine Generation ID Device
>         + *
>         + *  Copyright (C) 2017 Skyport Systems.
>         + *
>         + *  Author: Ben Warren <address@hidden>
>         + *
>         + * This work is licensed under the terms of the GNU GPL, version 2 or
>         later.
>         + * See the COPYING file in the top-level directory.
>         + *
>         + */
>         +
>         +#include "qemu/osdep.h"
>         +#include "qmp-commands.h"
>         +#include "hw/acpi/acpi.h"
>         +#include "hw/acpi/aml-build.h"
>         +#include "hw/acpi/vmgenid.h"
>         +#include "hw/nvram/fw_cfg.h"
>         +#include "sysemu/sysemu.h"
>         +
>         +void vmgenid_build_acpi(GArray *table_data, GArray *guid, BIOSLinker
>         *linker)
>         +{
>         +    Object *obj;
>         +    VmGenIdState *s;
>         +    Aml *ssdt, *dev, *scope, *method, *addr, *if_ctx;
>         +    uint32_t vgia_offset;
>         +
>         +    obj = find_vmgenid_dev(NULL);
>         +    assert(obj);
>         +    s = VMGENID(obj);
>         +
>         +    /* Fill in the GUID values */
>         +    if (guid->len != VMGENID_FW_CFG_SIZE) {
>         +        g_array_set_size(guid, VMGENID_FW_CFG_SIZE);
>         +    }
>         +    g_array_insert_vals(guid, VMGENID_GUID_OFFSET, s->guid.data, 16);
> 
> 
>     ARRAY_SIZE(s->guid.data);
> 
> 
> OK
> 
>         +
>         +    /* Put this in a separate SSDT table */
>         +    ssdt = init_aml_allocator();
>         +
>         +    /* Reserve space for header */
>         +    acpi_data_push(ssdt->buf, sizeof(AcpiTableHeader));
>         +
>         +    /* Storage for the GUID address */
>         +    vgia_offset = table_data->len +
>         +        build_append_named_dword(ssdt->buf, "VGIA");
>         +    scope = aml_scope("\\_SB");
>         +    dev = aml_device("VGEN");
>         +    aml_append(dev, aml_name_decl("_HID", aml_string("QEMUVGID")));
>         +    aml_append(dev, aml_name_decl("_CID", aml_string
>         ("VM_Gen_Counter")));
>         +    aml_append(dev, aml_name_decl("_DDN", aml_string
>         ("VM_Gen_Counter")));
>         +
>         +    /* Simple status method to check that address is linked and
>         non-zero */
>         +    method = aml_method("_STA", 0, AML_NOTSERIALIZED);
>         +    addr = aml_local(0);
>         +    aml_append(method, aml_store(aml_int(0xf), addr));
>         +    if_ctx = aml_if(aml_equal(aml_name("VGIA"), aml_int(0)));
>         +    aml_append(if_ctx, aml_store(aml_int(0), addr));
>         +    aml_append(method, if_ctx);
>         +    aml_append(method, aml_return(addr));
>         +    aml_append(dev, method);
>         +
>         +    /* the ADDR method returns two 32-bit words representing the 
> lower
>         and
>         +     * upper halves * of the physical address of the fw_cfg blob
>         +     * (holding the GUID) */
> 
> 
>     /*
>     * multiline comments
>     * look like this
>     */
> 
> 
> OK
> 
>         +    method = aml_method("ADDR", 0, AML_NOTSERIALIZED);
>         +
>         +    addr = aml_local(0);
>         +    aml_append(method, aml_store(aml_package(2), addr));
>         +
>         +    aml_append(method, aml_store(aml_add(aml_name("VGIA"),
>         +                                         
> aml_int(VMGENID_GUID_OFFSET),
>         NULL),
>         +                                 aml_index(addr, aml_int(0))));
>         +    aml_append(method, aml_store(aml_int(0), aml_index(addr, aml_int
>         (1))));
>         +    aml_append(method, aml_return(addr));
>         +
>         +    aml_append(dev, method);
>         +    aml_append(scope, dev);
>         +    aml_append(ssdt, scope);
>         +
>         +    /* attach an ACPI notify */
>         +    method = aml_method("\\_GPE._E05", 0, AML_NOTSERIALIZED);
>         +    aml_append(method, aml_notify(aml_name("\\_SB.VGEN"), aml_int
>         (0x80)));
>         +    aml_append(ssdt, method);
>         +
>         +    g_array_append_vals(table_data, ssdt->buf->data, ssdt->buf->len);
>         +
>         +    /* Allocate guest memory for the Data fw_cfg blob */
>         +    bios_linker_loader_alloc(linker, VMGENID_GUID_FW_CFG_FILE, guid,
>         4096,
>         +                             false /* page boundary, high memory */);
>         +
>         +    /* Patch address of GUID fw_cfg blob into the ADDR fw_cfg blob */
> 
> 
>     add ... so QEMU can write GUID there
> 
> 
> OK
> 
>         +    bios_linker_loader_add_pointer(linker,
>         +        VMGENID_ADDR_FW_CFG_FILE, 0, sizeof(uint32_t),
>         +        VMGENID_GUID_FW_CFG_FILE, 0, true);
>         +
>         +    /* Patch address of GUID fw_cfg blob into the AML */
> 
> 
>     add ... so OSPM can retrieve and read it
> 
> 
> OK
> 
>         +    bios_linker_loader_add_pointer(linker,
>         +        ACPI_BUILD_TABLE_FILE, vgia_offset, sizeof(uint32_t),
>         +        VMGENID_GUID_FW_CFG_FILE, 0, false);
>         +
>         +    build_header(linker, table_data,
>         +        (void *)(table_data->data + table_data->len - 
> ssdt->buf->len),
>         +        "SSDT", ssdt->buf->len, 1, NULL, "VMGENID");
>         +    free_aml_allocator();
>         +}
>         +
>         +void vmgenid_add_fw_cfg(FWCfgState *s, GArray *guid)
>         +{
>         +    Object *obj = find_vmgenid_dev(NULL);
>         +    assert(obj);
>         +    VmGenIdState *vms = VMGENID(obj);
>         +
>         +    /* Create a read-only fw_cfg file for GUID */
>         +    fw_cfg_add_file(s, VMGENID_GUID_FW_CFG_FILE, guid->data,
>         +                    VMGENID_FW_CFG_SIZE);
>         +    /* Create a read-write fw_cfg file for Address */
>         +    fw_cfg_add_file_callback(s, VMGENID_ADDR_FW_CFG_FILE, NULL, NULL,
> 
> 
>     Seems wrong. What if guest updates the address after command line
>     set it? You want a callback to copy guid there.
> 
> 
> Sure, I can do that.  My understanding was that this is a read callback, but 
> if
> it also is called upon a write, we should do what you suggest.

Hmm you are right. But we really need to call something
on write though - unlike read, it must be called after write.
Otherwise I don't see how it can work if you set gen id before
guest boots.

I guess this means we need yet another callback per file.
FWCfgWriteCallback ?

Can you implement this in hw/nvram/fw_cfg.c?
It's rather straight-forward to do.


> 
> 
>         +                             vms->vgia_le, sizeof(uint32_t), false);
> 
> 
>     Should be ARRAY_SIZE(vms->vgia_le).
> 
>     Also, I thought GUID is at an offset from the beginning
>     in order to trick OVMF, isn't it?
> 
> 
> The offset is taken into account in the GUID fw_cfg file.  The writing to 
> guest
> memory, we add the offset to VGIA.

I keep forgetting it's the address. Really please rename it
using full words.


> 
>         +}
>         +
>         +static void vmgenid_update_guest(VmGenIdState *s)
>         +{
>         +    Object *obj = object_resolve_path_type("", TYPE_ACPI_DEVICE_IF,
>         NULL);
>         +    uint32_t vgia;
>         +
>         +    if (obj) {
>         +        /* Write the GUID to guest memory */
>         +        memcpy(&vgia, s->vgia_le, sizeof(vgia));
>         +        vgia = le32_to_cpu(vgia);
>         +        if (vgia) {
> 
> 
>     add a comment saying 0 means bios did not run yet.
> 
> OK
> 
> 
> 
>         +            cpu_physical_memory_write(vgia + VMGENID_GUID_OFFSET,
>         +                                      s->guid.data, sizeof(s->
>         guid.data));
> 
> 
>     Avoid this. You want dma.h APIs.
> 
> I’ll have a look at those.  This function was recommended to me in an earlier
> patch version.
> 
> 
> 
>         +            /* Send _GPE.E05 event */
>         +            acpi_send_event(DEVICE(obj), ACPI_VMGENID_CHANGE_STATUS);
>         +        }
>         +    }
>         +}
>         +
>         +static void vmgenid_set_guid(Object *obj, const char *value, Error
>         **errp)
>         +{
>         +    VmGenIdState *s = VMGENID(obj);
>         +
>         +    if (!strncmp(value, "auto", 4)) {
> 
> 
>     I'd use strcmp here.
> 
> OK
> 
> 
> 
>         +        qemu_uuid_generate(&s->guid);
>         +    } else if (qemu_uuid_parse(value, &s->guid) < 0) {
>         +        error_setg(errp, "'%s. %s': Failed to parse GUID string: %s",
>         +                   object_get_typename(OBJECT(s)), VMGENID_GUID,
>         value);
>         +        return;
>         +    }
>         +    /* QemuUUID has the first three words as big-endian, and expect
>         that any
>         +     * GUIDs passed in will always be BE.  The guest, however will
>         expect
>         +     * the fields to be little-endian, so store that way internally.
> 
> 
>     This makes my head spin. It's the actual guid, right? Only place we need 
> it
>     is when
>     we copy it into guest memory. So swap there -
>     and do it to a copy so you won't need these comments.
> 
> I understand.  I wanted to only do the swap at one place and decided to do it
> closest to the user interface, but can do it at the other end instead.
> 
> 
> 
>         Make
>         +     * sure to swap back whenever reporting via monitor */
> 
> 
>     And what code does this swap back?
> 
> A later patch where the QMP code is added.  But I’ll remove that necessity.
> 
> 
> 
>         +    qemu_uuid_bswap(&s->guid);
>         +
>         +    /* Send the ACPI notify */
>         +    vmgenid_update_guest(s);
>         +}
>         +
>         +/* After restoring an image, we need to update the guest memory and
>         notify
>         + * it of a potential change to VM Generation ID */
>         +static int vmgenid_post_load(void *opaque, int version_id)
>         +{
>         +    VmGenIdState *s = opaque;
>         +    vmgenid_update_guest(s);
>         +    return 0;
>         +}
>         +
>         +static const VMStateDescription vmstate_vmgenid = {
>         +    .name = "vmgenid",
>         +    .version_id = 1,
>         +    .minimum_version_id = 1,
>         +    .post_load = vmgenid_post_load,
>         +    .fields = (VMStateField[]) {
>         +        VMSTATE_UINT8_ARRAY(vgia_le, VmGenIdState, sizeof(uint32_t)),
>         +        VMSTATE_END_OF_LIST()
>         +    },
>         +};
>         +
>         +static void vmgenid_initfn(Object *obj)
>         +{
>         +    object_property_add_str(obj, VMGENID_GUID, NULL, 
> vmgenid_set_guid,
>         NULL);
>         +}
>         +
>         +static void vmgenid_device_class_init(ObjectClass *klass, void *data)
>         +{
>         +    DeviceClass *dc = DEVICE_CLASS(klass);
>         +
>         +    dc->vmsd = &vmstate_vmgenid;
>         +}
>         +
>         +static const TypeInfo vmgenid_device_info = {
>         +    .name          = VMGENID_DEVICE,
>         +    .parent        = TYPE_SYS_BUS_DEVICE,
>         +    .instance_size = sizeof(VmGenIdState),
>         +    .instance_init = vmgenid_initfn,
>         +    .class_init    = vmgenid_device_class_init,
>         +};
>         +
>         +static void vmgenid_register_types(void)
>         +{
>         +    type_register_static(&vmgenid_device_info);
>         +}
>         +
>         +type_init(vmgenid_register_types)
>         diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>         index 78a1d84..4c40f76 100644
>         --- a/hw/i386/acpi-build.c
>         +++ b/hw/i386/acpi-build.c
>         @@ -42,6 +42,7 @@
>         #include "hw/acpi/memory_hotplug.h"
>         #include "sysemu/tpm.h"
>         #include "hw/acpi/tpm.h"
>         +#include "hw/acpi/vmgenid.h"
>         #include "sysemu/tpm_backend.h"
>         #include "hw/timer/mc146818rtc_regs.h"
>         #include "sysemu/numa.h"
>         @@ -2653,6 +2654,11 @@ void acpi_build(AcpiBuildTables *tables,
>         MachineState *machine)
>             acpi_add_table(table_offsets, tables_blob);
>             build_madt(tables_blob, tables->linker, pcms);
> 
>         +    if (find_vmgenid_dev(NULL)) {
>         +        acpi_add_table(table_offsets, tables_blob);
>         +        vmgenid_build_acpi(tables_blob, tables->vmgenid, tables->
>         linker);
>         +    }
>         +
>             if (misc.has_hpet) {
>                 acpi_add_table(table_offsets, tables_blob);
>                 build_hpet(tables_blob, tables->linker);
>         @@ -2859,6 +2865,10 @@ void acpi_setup(void)
>             fw_cfg_add_file(pcms->fw_cfg, ACPI_BUILD_TPMLOG_FILE,
>                             tables.tcpalog->data, acpi_data_len
>         (tables.tcpalog));
> 
>         +    if (find_vmgenid_dev(NULL)) {
>         +        vmgenid_add_fw_cfg(pcms->fw_cfg, tables.vmgenid);
>         +    }
>         +
>             if (!pcmc->rsdp_in_ram) {
>                 /*
>                  * Keep for compatibility with old machine types.
>         diff --git a/include/hw/acpi/acpi_dev_interface.h b/include/hw/acpi/
>         acpi_dev_interface.h
>         index 71d3c48..3c2e4e9 100644
>         --- a/include/hw/acpi/acpi_dev_interface.h
>         +++ b/include/hw/acpi/acpi_dev_interface.h
>         @@ -11,6 +11,7 @@ typedef enum {
>             ACPI_CPU_HOTPLUG_STATUS = 4,
>             ACPI_MEMORY_HOTPLUG_STATUS = 8,
>             ACPI_NVDIMM_HOTPLUG_STATUS = 16,
>         +    ACPI_VMGENID_CHANGE_STATUS = 32,
>         } AcpiEventStatusBits;
> 
>         #define TYPE_ACPI_DEVICE_IF "acpi-device-interface"
>         diff --git a/include/hw/acpi/vmgenid.h b/include/hw/acpi/vmgenid.h
>         new file mode 100644
>         index 0000000..b60437a
>         --- /dev/null
>         +++ b/include/hw/acpi/vmgenid.h
>         @@ -0,0 +1,37 @@
>         +#ifndef ACPI_VMGENID_H
>         +#define ACPI_VMGENID_H
>         +
>         +#include "hw/acpi/bios-linker-loader.h"
>         +#include "hw/sysbus.h"
>         +#include "qemu/uuid.h"
>         +
>         +#define VMGENID_DEVICE           "vmgenid"
>         +#define VMGENID_GUID             "guid"
>         +#define VMGENID_GUID_FW_CFG_FILE      "etc/vmgenid"
> 
> 
>     Maybe vmgenid_guid ?
> 
> Sure.
> 
> 
> 
>         +#define VMGENID_ADDR_FW_CFG_FILE      "etc/vmgenid_addr"
>         +
>         +#define VMGENID_FW_CFG_SIZE      4096 /* Occupy a page of memory */
>         +#define VMGENID_GUID_OFFSET      40   /* allow space for
>         +                                       * OVMF SDT Header Probe
>         Supressor */
> 
> 
>     ACPI header size is 36 bytes. I'd expect just to use that.
>     Where does 40 come from? I think it's an 8 bytes alignment requirement.
> 
> 
> The number 40 was asked for by Laszlo for the OVMF SDT Header Probe 
> Suppressor,
> which I don’t know anything about.

I think I do though :)

>  This GUID isn’t going in an ACPI table, so
> I’m not sure what you mean here.  We allocate on a page boundary and 40 bytes
> in should be 8-byte aligned.
> 
>     So do QEMU_ALIGN_UP(sizeof(AcpiTableHeader), 8)
> 
>     Add a comment explaining that 8.

Laszlo could you suggest a comment explaining a bit about what
OVMF does here?

> 
>         +
>         +void vmgenid_add_fw_cfg(FWCfgState *s, GArray *guid);
>         +void vmgenid_build_acpi(GArray *table_data, GArray *guid, BIOSLinker
>         *linker);
>         +
>         +#define VMGENID(obj) OBJECT_CHECK(VmGenIdState, (obj), 
> VMGENID_DEVICE)
>         +
>         +typedef struct VmGenIdState {
>         +    SysBusDevice parent_obj;
>         +    QemuUUID guid;
>         +    uint8_t vgia_le[4];
> 
> 
>     Please give this fields a better name. Is this the address?
>     Pls add comments, too.
> 
> 
> This variable name was suggested by Laszlo.  the ‘a’ in ‘vgia’ refers to
> address, but I’ll add some comments.

vmgenid_addr_le?


>     How about we make it 8 byte so it's future proof?
> 
> I can do that, but a previous conversation we had made it clear that guests
> would never allocate above 4GB so 64 bits wasn’t necessary.

Right, it's just very painful to change once we make it 32 bit.

>     alternatively put it in a ram block instead.
> 
> 
>         +} VmGenIdState;
>         +
>         +static Object *find_vmgenid_dev(Error **errp)
>         +{
>         +    Object *obj = object_resolve_path_type("", VMGENID_DEVICE, NULL);
>         +    if (!obj && errp) {
>         +        error_setg(errp, "%s is not found", VMGENID_DEVICE);
>         +    }
>         +    return obj;
>         +}
>         +
>         +#endif
>         -- 
>         2.7.4
> 
>