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Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' c
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From: |
Michael S. Tsirkin |
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Subject: |
Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command |
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Date: |
Wed, 15 Feb 2017 23:09:37 +0200 |
On Wed, Feb 15, 2017 at 10:44:05AM -0800, Ben Warren wrote:
>
> On Feb 15, 2017, at 10:35 AM, Igor Mammedov <address@hidden> wrote:
>
> On Wed, 15 Feb 2017 10:14:55 -0800
> Ben Warren <address@hidden> wrote:
>
>
> On Feb 15, 2017, at 10:06 AM, Michael S. Tsirkin <address@hidden>
> wrote:
>
> On Wed, Feb 15, 2017 at 09:54:08AM -0800, Ben Warren wrote:
>
>
> On Feb 15, 2017, at 9:43 AM, Igor Mammedov <
> address@hidden> wrote:
>
> On Wed, 15 Feb 2017 18:39:06 +0200
> "Michael S. Tsirkin" <address@hidden> wrote:
>
>
> On Wed, Feb 15, 2017 at 04:56:02PM +0100, Igor Mammedov
> wrote:
>
> On Wed, 15 Feb 2017 17:30:00 +0200
> "Michael S. Tsirkin" <address@hidden> wrote:
>
>
> On Wed, Feb 15, 2017 at 04:22:25PM +0100, Igor
> Mammedov wrote:
>
>
> On Wed, 15 Feb 2017 15:13:20 +0100
> Laszlo Ersek <address@hidden> wrote:
>
>
> Commenting under Igor's reply for
> simplicity
>
> On 02/15/17 11:57, Igor Mammedov wrote:
>
>
> On Tue, 14 Feb 2017 22:15:43 -0800
> address@hidden wrote:
>
>
> From: Ben Warren <
> address@hidden>
>
> This is similar to the existing
> 'add pointer'
> functionality, but instead
> of instructing the guest (BIOS
> or
> UEFI) to
> patch memory, it instructs
> the guest to write the pointer
> back to QEMU via
> a writeable fw_cfg file.
>
> Signed-off-by: Ben Warren <
> address@hidden>
> ---
> hw/acpi/bios-linker-loader.c
> | 58
>
> ++++++++++++++++++++++++++++++++++--
> include/hw/acpi/
> bios-linker-loader.h | 6 ++++
> 2 files changed, 61 insertions
> (+), 3 deletions
> (-)
>
> diff --git a/hw/acpi/
> bios-linker-loader.c b/hw/
> acpi/bios-linker-loader.c
> index d963ebe..5030cf1 100644
> --- a/hw/acpi/
> bios-linker-loader.c
> +++ b/hw/acpi/
> bios-linker-loader.c
> @@ -78,6 +78,19 @@ struct
> BiosLinkerLoaderEntry
> {
> uint32_t length;
> } cksum;
>
> + /*
> + *
> COMMAND_WRITE_POINTER
> - write the
> fw_cfg file (originating from
> + * @dest_file) at
> @wr_pointer.offset,
> by adding a pointer to the table
> + * originating from
> @src_file. 1,2,4
> or 8 byte unsigned
> + * addition is used
> depending on
> @wr_pointer.size.
> + */
>
>
> The words "adding" and "addition" are
> causing confusion
> here.
>
> In all of the previous discussion,
> *addition* was out
> of scope from
> WRITE_POINTER. Again, the firmware is
> specifically not
> required to
> *read* any part of the fw_cfg blob
> identified by
> "dest_file".
>
> WRITE_POINTER instructs the firmware to
> return the
> allocation address of
> the downloaded "src_file" to QEMU. Any
> necessary
> runtime subscripting
> within "src_file" is to be handled by
> QEMU code
> dynamically.
>
> For example, consider that "src_file"
> has
> *several*
> fields that QEMU
> wants to massage; in that case, indexing
> within QEMU
> code with field
> offsets is simply unavoidable.
>
> what I don't like here is that this indexing
> would be
> rather fragile
> and has to be done in different parts of
> QEMU
> /device, AML
> /.
>
> I'd prefer this helper function to have the
> same
> @src_offset
> behavior as ADD_POINTER where patched
> address
> could point
> to
> any part of src_file i.e. not just
> beginning.
>
>
>
>
>
> /*
> * COMMAND_ADD_POINTER - patch the table
> (originating
> from
> * @dest_file) at @pointer.offset, by
> adding a pointer
> to the table
> * originating from @src_file. 1,2,4 or 8
> byte unsigned
> * addition is used depending on
> @pointer.size.
> */
>
> so the way ADD works is
> read at offset
> add table address
> write result at offset
>
> in other words it is always beginning of table
> that is added.
>
> more exactly it's, read at
> src_offset = *(dst_blob_ptr+dst_offset)
> *(dst_blob+dst_offset) = src_blob_ptr + src_offset
>
>
> Would the following be acceptable?
>
>
> * COMMAND_WRITE_POINTER - update the
> fw_cfg file
> (originating from
> * @dest_file) at @wr_pointer.offset, by
> writing a
> pointer to the table
> * originating from @src_file. 1,2,4 or 8
> byte unsigned
> value
> * is written depending on
> @wr_pointer.size.
>
> it looses 'adding' part of ADD_POINTER command which
> handles
> src_offset,
> however implementing adding part looks a bit
> complicated
> as patched blob (dst) is not in guest memory but in
> QEMU and
> on reset *(dst_blob+dst_offset) should be reset to
> src_offset.
> Considering dst file could be device specific memory
> (field/blob/
> whatever)
> it could be hard to track/notice proper reset
> behavior.
>
> So now I'm not sure if src_offset is worth adding.
>
>
> Right. Let's just do this math in QEMU if we have to.
>
> Math complicates QEMU code though and not only QMEMU but AML
> code as well.
> Considering that we are adding a new command and don't have
> to keep
> any sort of compatibility we can pass src_offset as part
> of command instead of hiding it inside of dst_file.
> Something like this:
>
> /*
> * COMMAND_WRITE_POINTER - write the fw_cfg file
> (originating from
> * @dest_file) at @wr_pointer.offset, by writing a
> pointer to
> @src_offset
> * within the table originating from @src_file. 1,2,4
> or 8 byte
> unsigned
> * addition is used depending on @wr_pointer.size.
> */
> struct {
> char dest_file[BIOS_LINKER_LOADER_FILESZ];
> char src_file[BIOS_LINKER_LOADER_FILESZ];
> - uint32_t offset;
> + uint32_t dst_offset;
> + uint32_t src_offset;
> uint8_t size;
> } wr_pointer;
>
>
> OK, this is easy enough to do and maybe we’ll have a use case
> in the future.
> I’ll make this change in v7
>
>
>
> So if you do, you want to set it to VMGENID_GUID_OFFSET.
>
>
> Oh, I was going to set it to 0 since that doesn’t require any other
> changes (other than to SeaBIOS)
This is equivalent to not adding this field at all.
If we do add it we better have at least some users
set it to something non-zero otherwise we do not
really know whether it works.
> it should be changed in following places:
>
> bios_linker_loader_write_pointer(linker,
> VMGENID_ADDR_FW_CFG_FILE, 0, sizeof(uint64_t),
> - VMGENID_GUID_FW_CFG_FILE);
> + VMGENID_GUID_FW_CFG_FILE, VMGENID_GUID_OFFSET);
>
> ...
> - cpu_physical_memory_write(vmgenid_addr + VMGENID_GUID_OFFSET,
> + cpu_physical_memory_write(vmgenid_addr,
> guid_le.data, sizeof(guid_le.data));
>
>
> OK, the more places I can get rid of this goofy offset the better. Just to be
> clear, the address that gets patched into AML (via the add_pointer() call)
> remains at the beginning of /etc/vmgenid_guid, right?
It's up to you really but OVMF wants the beginning I think.
>
>
>
>
>
>
>
>
>
>
>
> (1) So, the above looks correct, but
> please replace
> "adding" with
> "storing", and "unsigned addition" with
> "store".
>
> Side point: the case for ADD_POINTER is
> different;
> there we patch
> several individual ACPI objects. The
> fact
> that I
> requested explicit
> addition within the ADDR method, as
> opposed to
> pre-setting VGIA to a
> nonzero offset, is an *incidental*
> limitation (coming
> from the OVMF ACPI
> SDT header probe suppressor), and we'll
> likely fix that
> up later, with
> ALLOCATE command hints or something like
> that. However,
> in
> WRITE_POINTER, asking for the exact
> allocation address
> of "src_file" is
> an *inherent* characteristic.
>
> For reference, this is the command's
> description from
> the (not as yet
> posted) OVMF series:
>
> // QemuLoaderCmdWritePointer: the bytes
> at
> //
> [PointerOffset..PointerOffset+PointerSize) in the
> writeable fw_cfg
> // file PointerFile are to receive the
> absolute address
> of PointeeFile,
> // as allocated and downloaded by the
> firmware. Store
> the base address
> // of where PointeeFile's contents have
> been placed
> (when
> // QemuLoaderCmdAllocate has been
> executed for
> PointeeFile) to this
> // portion of PointerFile.
> //
> // This command is similar to
> QemuLoaderCmdAddPointer;
> the difference is
> // that the "pointer to patch" does not
> exist in
> guest-physical address
> // space, only in "fw_cfg file space".
> In
> addition, the
> "pointer to
> // patch" is not initialized by QEMU
> with
> a possibly
> nonzero offset
> // value: the base address of the memory
> allocated for
> downloading
> // PointeeFile shall not increment the
> pointer, but
> overwrite it.
>
> In the last SeaBIOS patch series, namely
>
> [SeaBIOS] [PATCH v3 2/2] QEMU fw_cfg:
> Add
> command to
> write back address
> of file
>
> function romfile_loader_write_pointer()
> implemented
> just that plain
> store (not an addition), and that was
> exactly right.
>
> Continuing:
>
>
> + struct {
> + char dest_file
> [BIOS_LINKER_LOADER_FILESZ];
> + char src_file
> [BIOS_LINKER_LOADER_FILESZ];
> + uint32_t offset;
> + uint8_t size;
> + } wr_pointer;
> +
> /* padding */
> char pad[124];
> };
> @@ -85,9 +98,10 @@ struct
> BiosLinkerLoaderEntry
> {
> typedef struct
> BiosLinkerLoaderEntry
> BiosLinkerLoaderEntry;
>
> enum {
> -
> BIOS_LINKER_LOADER_COMMAND_ALLOCATE =
> 0x1,
> -
> BIOS_LINKER_LOADER_COMMAND_ADD_POINTER =
> 0x2,
> -
> BIOS_LINKER_LOADER_COMMAND_ADD_CHECKSUM =
> 0x3,
> +
> BIOS_LINKER_LOADER_COMMAND_ALLOCATE
> = 0x1,
> +
> BIOS_LINKER_LOADER_COMMAND_ADD_POINTER
> = 0x2,
> +
> BIOS_LINKER_LOADER_COMMAND_ADD_CHECKSUM
> = 0x3,
> +
> BIOS_LINKER_LOADER_COMMAND_WRITE_POINTER
> = 0x4,
> };
>
> enum {
> @@ -278,3 +292,41 @@ void
> bios_linker_loader_add_pointer
> (BIOSLinker
> *linker,
>
> g_array_append_vals(linker->
> cmd_blob, &
> entry, sizeof entry);
> }
> +
> +/*
> + *
> bios_linker_loader_write_pointer: ask guest
> to write a pointer to the
> + * source file into the
> destination file, and
> write it back to QEMU via
> + * fw_cfg DMA.
> + *
> + * @linker: linker object
> instance
> + * @dest_file: destination file
> that must be
> written
> + * @dst_patched_offset:
> location
> within
> destination file blob to be
> patched
> + * with
> the
> pointer to
> @src_file, in bytes
> + * @dst_patched_offset_size:
> size of the
> pointer to be patched
> + * at
> @dst_patched_offset
> in @dest_file blob, in bytes
> + * @src_file: source file who's
> address must
> be taken
> + */
> +void
> bios_linker_loader_write_pointer
> (BIOSLinker *linker,
> +
> const char
> *dest_file,
> +
> uint32_t
> dst_patched_offset,
> +
> uint8_t
> dst_patched_size,
> +
> const char
> *src_file)
>
> API is missing "src_offset" even
> though it's not
> used in this series,
> a patch on top to fix it up is ok
> for
> me as far as
> Seabios/OVMF
> counterpart can handle src_offset
> correctly from
> starters.
>
>
> According to the above, it is the right
> thing not to
> add "src_offset"
> here. The documentation on the command
> is
> slightly
> incorrect (and causes
> confusion), but the helper function's
> signature and
> comments are okay.
>
>
>
>
> +{
> + BiosLinkerLoaderEntry
> entry;
> + const BiosLinkerFileEntry
> *source_file =
> + bios_linker_find_file
> (linker,
> src_file);
> +
> + assert(source_file);
>
>
> I wish we kept the following asserts
> from
> bios_linker_loader_add_pointer():
>
> assert(dst_patched_offset <
> dst_file->
> blob->len);
> assert(dst_patched_offset +
> dst_patched_size <=
> dst_file->blob->len);
>
> Namely, just because the dst_file is
> never supposed to
> be downloaded by
> the firmware, it still remains a
> requirement that the
> "dst file offset
> range" that is to be rewritten *do fall*
> within the dst
> file.
>
> Nonetheless, this is not critical. (OVMF
> at least
> verifies it anyway.)
>
> Summary (from my side anyway): I feel
> that the
> documentation of the new
> command is very important. Please fix it
> up as
> suggested under (1), in
> v7. Regarding the asserts, I'll let you
> decide.
>
> With the documentation fixed up:
>
> Reviewed-by: Laszlo Ersek <
> address@hidden>
>
> (If you don't wish to post a v7, I'm
> also
> completely
> fine if Michael or
> someone else fixes up the docs as
> proposed in (1),
> before committing the
> patch.)
>
> Thanks!
> Laszlo
>
>
> + memset(&entry, 0, sizeof
> entry);
> + strncpy
> (entry.wr_pointer.dest_file,
> dest_file,
> + sizeof
> entry.wr_pointer.dest_file
> - 1);
> + strncpy
> (entry.wr_pointer.src_file,
> src_file,
> + sizeof
> entry.wr_pointer.src_file -
> 1);
> + entry.command = cpu_to_le32
>
> (BIOS_LINKER_LOADER_COMMAND_WRITE_POINTER);
> + entry.wr_pointer.offset =
> cpu_to_le32
> (dst_patched_offset);
> + entry.wr_pointer.size =
> dst_patched_size;
> + assert(dst_patched_size ==
> 1
> ||
> dst_patched_size == 2 ||
> + dst_patched_size ==
> 4
> ||
> dst_patched_size == 8);
> +
> +
> g_array_append_vals(linker->
> cmd_blob, &
> entry, sizeof entry);
> +}
> diff --git a/include/hw/acpi/
> bios-linker-loader.h
> b/include/hw
> /acpi/
> bios-linker-loader.h
> index fa1e5d1..f9ba5d6 100644
> --- a/include/hw/acpi/
> bios-linker-loader.h
> +++ b/include/hw/acpi/
> bios-linker-loader.h
> @@ -26,5 +26,11 @@ void
> bios_linker_loader_add_pointer
> (BIOSLinker
> *linker,
>
> const
> char
> *src_file,
>
> uint32_t
> src_offset);
>
> +void
> bios_linker_loader_write_pointer
> (BIOSLinker *linker,
> +
> const
> char *dest_file,
> +
> uint32_t
> dst_patched_offset,
> +
> uint8_t
> dst_patched_size,
> +
> const
> char *src_file);
> +
> void bios_linker_loader_cleanup
> (BIOSLinker
> *linker);
> #endif
>
>
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, (continued)
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Michael S. Tsirkin, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Igor Mammedov, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Michael S. Tsirkin, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Laszlo Ersek, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Igor Mammedov, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Ben Warren, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Michael S. Tsirkin, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Ben Warren, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Igor Mammedov, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Ben Warren, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Michael S. Tsirkin, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Igor Mammedov, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Ben Warren, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Ben Warren, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Igor Mammedov, 2017/02/16
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Eric Blake, 2017/02/16
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Michael S. Tsirkin, 2017/02/15
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Igor Mammedov, 2017/02/16
- Re: [Qemu-devel] [PATCH v6 1/7] linker-loader: Add new 'write pointer' command, Laszlo Ersek, 2017/02/16
[Qemu-devel] [PATCH v6 5/7] qmp/hmp: add query-vm-generation-id and 'info vm-generation-id' commands, ben, 2017/02/15