Re: [Qemu-devel] RFC: guest-side retrieval of fw_cfg file

[Richard W.M. Jones]

On Mon, Jul 13, 2015 at 04:09:37PM -0400, Gabriel L. Somlo wrote:
> 3. I'm currently only handling x86 and I/O ports. I could drop the
>    fw_cfg_dmi_whitelist and just check the signature, using mmio where
>    appropriate, but I don't have a handy-dandy set of VMs for those
>    architectures on which I could test. Wondering if that's something
>    we should have before I officially try to submit this to the kernel,
>    or whether it could wait for a second iteration.

  $ virt-builder --arch armv7l fedora-22
or:
  $ virt-builder --arch aarch64 fedora-22
then:
  $ virt-builder --get-kernel fedora-22.img

and then boot is using the right qemu command, probably something
like:

  $ qemu-system-arm \
      -M virt,accel=tcg \
      -cpu cortex-a15 \
      -kernel vmlinuz-4.0.4-301.fc22.armv7hl+lpae \
      -initrd initramfs-4.0.4-301.fc22.armv7hl+lpae.img \
      -append "console=ttyAMA0 root=/dev/vda3 ro" \
      -drive file=fedora-22.img,if=none,id=hd \
      -device virtio-blk-device,drive=hd \
      -serial stdio

The root password is printed in virt-builder output.

> /* read chunk of given fw_cfg blob (caller responsible for sanity-check) */
> static inline void fw_cfg_read_blob(uint16_t select,
>                                    void *buf, loff_t pos, size_t count)
> {
>       mutex_lock(&fw_cfg_dev_lock);
>       outw(select, FW_CFG_PORT_CTL);
>       while (pos-- > 0)
>               inb(FW_CFG_PORT_DATA);
>       insb(FW_CFG_PORT_DATA, buf, count);
>       mutex_unlock(&fw_cfg_dev_lock);
> }

How slow is this?

Rich.

-- 
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