From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60274) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YIHT6-0000fY-8H for qemu-devel@nongnu.org; Mon, 02 Feb 2015 08:55:13 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YIHT0-0005uU-As for qemu-devel@nongnu.org; Mon, 02 Feb 2015 08:55:11 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56267) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YIHT0-0005sm-4L for qemu-devel@nongnu.org; Mon, 02 Feb 2015 08:55:06 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t12Dt55O016541 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Mon, 2 Feb 2015 08:55:05 -0500 Date: Mon, 2 Feb 2015 14:55:02 +0100 From: Igor Mammedov Message-ID: <20150202145502.72dd11cd@nial.brq.redhat.com> In-Reply-To: <54CF7803.7020906@redhat.com> References: <1418745044-3986-1-git-send-email-ghammer@redhat.com> <1418745044-3986-3-git-send-email-ghammer@redhat.com> <20150122145246.5d020fab@nial.brq.redhat.com> <54CE227A.9020000@redhat.com> <20150202134635.434233f7@nial.brq.redhat.com> <54CF7803.7020906@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH V11 2/3] i386: Add a Virtual Machine Generation ID device List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gal Hammer Cc: qemu-devel@nongnu.org, mst@redhat.com On Mon, 02 Feb 2015 15:13:39 +0200 Gal Hammer wrote: > On 02/02/2015 14:46, Igor Mammedov wrote: > > On Sun, 01 Feb 2015 14:56:26 +0200 > > Gal Hammer wrote: > > > >> On 22/01/2015 15:52, Igor Mammedov wrote: > >>> On Tue, 16 Dec 2014 17:50:43 +0200 > >>> Gal Hammer wrote: > >>> > >>>> Based on Microsoft's sepecifications (paper can be dowloaded from > >>>> http://go.microsoft.com/fwlink/?LinkId=260709), add a device > >>>> description to the SSDT ACPI table and its implementation. > >>>> > >>>> The GUID is set using a global "vmgenid.uuid" parameter. > >>>> > >>>> Signed-off-by: Gal Hammer > >>>> > >>> > >>>> --- a/hw/i386/acpi-build.c > >>>> +++ b/hw/i386/acpi-build.c > >>>> @@ -257,6 +257,7 @@ static void acpi_get_pci_info(PcPciInfo *info) > >>>> #define ACPI_BUILD_TABLE_FILE "etc/acpi/tables" > >>>> #define ACPI_BUILD_RSDP_FILE "etc/acpi/rsdp" > >>>> #define ACPI_BUILD_TPMLOG_FILE "etc/tpm/log" > >>>> +#define ACPI_BUILD_VMGENID_FILE "etc/vm-generation-id" > >>>> > >>>> static void > >>>> build_header(GArray *linker, GArray *table_data, > >>>> @@ -1068,6 +1069,8 @@ build_ssdt(GArray *table_data, GArray *linker, > >>>> { > >>>> MachineState *machine = MACHINE(qdev_get_machine()); > >>>> uint32_t nr_mem = machine->ram_slots; > >>>> + uint32_t vm_gid_physical_address; > >>>> + uint32_t vm_gid_offset = 0; > >>>> unsigned acpi_cpus = guest_info->apic_id_limit; > >>>> int ssdt_start = table_data->len; > >>>> uint8_t *ssdt_ptr; > >>>> @@ -1096,6 +1099,21 @@ build_ssdt(GArray *table_data, GArray *linker, > >>>> ACPI_BUILD_SET_LE(ssdt_ptr, sizeof(ssdp_misc_aml), > >>>> ssdt_isa_pest[0], 16, misc->pvpanic_port); > >>>> > >>>> + if (vm_generation_id_set()) { > >>>> + vm_gid_physical_address = ssdt_start + ssdt_acpi_vm_gid_addr[0]; > >>>> + bios_linker_loader_alloc(linker, ACPI_BUILD_VMGENID_FILE, 8, true); > >>>> + bios_linker_loader_add_pointer(linker, ACPI_BUILD_VMGENID_FILE, > >>>> + ACPI_BUILD_TABLE_FILE, > >>>> + table_data, > >>>> + &vm_gid_offset, > >>>> + sizeof(vm_gid_offset)); > >>> could some explain how this pointer magic works, > >> > >> I can try, but don't you think that a magic is gone once explained? ;-) > >> > >>> From my weak understanding it seems broken. > >>> Lets see: > >>> > >>> [1] &vm_gid_offset - must be pointer inside of dest_file blob (ACPI_BUILD_VMGENID_FILE) > >>> [2] vm_gid_offset - should hold offset of the place inside of src_file > >>> (ACPI_BUILD_TABLE_FILE) where to pointer inside of dest_file should point to > >> > >> The vm_gid_offset should point where in the ACPI_BUILD_VMGENID_FILE the > >> VM's GUID is stored. At the moment, it should always be zero because the > >> GUID is stored at the begging of the ACPI_BUILD_VMGENID_FILE. > >> > >>> > >>> now: > >>> vm_gid_physical_address - holds [2] i.e. offset of VGIA constant in inside SSDT in ACPI_BUILD_TABLE_FILE. > >>> > >>>> + ACPI_BUILD_SET_LE(ssdt_ptr, sizeof(ssdp_misc_aml), > >>>> + ssdt_acpi_vm_gid_addr[0], 32, vm_gid_physical_address); > >>> Then we write this offset into VGIA in ACPI_BUILD_TABLE_FILE. > >> > >> Yes. This offset is later patched by the linker to the full physical > >> address. > >> > >>> After BIOS loads tables it's going to patch at > >>> [3] ACPI_BUILD_VMGENID_FILE + (&vm_gid_offset - table_data->data) /* only god knows where it will be/ > >>> > >>> and on top of it write in it value: > >>> *(ACPI_BUILD_TABLE_FILE + *[3]) > >> > >> We know exactly where it is, no need to call for god's help :-). > >> > >>> This approach in general of patching arbitrary place in AML blob > >>> to get PHY addr of buffer with UUID, is quite a hack, especially > >>> in light of that we are trying to hide all direct access to AML > >>> blobs with related pointer arithmetic and manual patching. > >>> > >>> Why not reserve some potion of RAM and pass to BIOS/guest > >>> a reservation so it won't be part of AddressRangeMemory or > >>> AddressRangeACPI as MS spec requires? Then you won't need > >>> jump all above hoops to just get buffer's PHY addr. > >> > >> I'll be glad to hear a new idea that I didn't already try in one of > >> other previous patches. The problem is that the specification requires > >> working with a physical address, so it must be allocated from inside the > >> guest. Since the OS is not exist in this stage and I also don't want to > >> write a special driver just to allocate this buffer I had to choose this > >> approach. > > how about creating device which will map 4K MMIO region in PCI hole > > address space and passing it as a reservation via e820 table we have in QEMU. > > Then address could be directly built in ACPI tables as constant value > > at the time of ACPI tables creation. > > Isn't this will cause a VMEXIT when the guest is reading the GUID? If it > is then this idea was already presented and Michael didn't approve it. It will, but is it performance critical? VM supposed to read it at start-up and on getting notification. So I think VMEXIT in this case is not sufficient to drop simple and strait-forward design. BTW: For start-up fw_cfg file is not any way better, it's also causes VMEXIT for every byte it reads from it. > > > That way it would be possible to get address of buffer without > > firmware + guest OS doing anything and going through quite complex > > chain for getting buffer address (qemu->bios->OSPM->qemu). > > If you go current route, it would be needed to teach linker a new command > > to make reservation in E820 so that allocated buffer won't be part of > > of AddressRangeMemory as required by spec or anything else. > > Which would make already hard to understand/use correctly linker API > > even more complex. > > > > > >> > >>>> > >>> [...] > >>>> typedef > >>>> @@ -1790,6 +1811,11 @@ void acpi_setup(PcGuestInfo *guest_info) > >>>> fw_cfg_add_file(guest_info->fw_cfg, ACPI_BUILD_TPMLOG_FILE, > >>>> tables.tcpalog->data, acpi_data_len(tables.tcpalog)); > >>>> > >>>> + /* Add a 128-bit fw cfg file which stores the VM generation id. */ > >>>> + g_array_set_size(tables.vmgenid, 16); > >>>> + fw_cfg_add_file(guest_info->fw_cfg, ACPI_BUILD_VMGENID_FILE, > >>>> + tables.vmgenid->data, tables.vmgenid->len); > >>> shouldn't it be migratable? /i.e. acpi_add_rom_blob(...)/ > >>> > >> > >> I'm not too familiar with the migration process, but I assume that this > >> memory will be copied as part of the guest memory. > >> > >> Gal. > >> > > >