Re: [PATCH] x86: temporarily remove all attempts to provide setup_data

[Nathan Chancellor]

On Wed, Feb 08, 2023 at 11:14:23AM -0700, Nathan Chancellor wrote:
> On Wed, Feb 08, 2023 at 03:08:35PM -0300, Jason A. Donenfeld wrote:
> > All attempts at providing setup_data have been made as an iteration on
> > whatever was there before, stretching back to the original
> > implementation used for DTBs that [mis]used the kernel image itself.
> > We've now had a dozen rounds of bugs and hacks, and the result is
> > turning into a pile of unmaintainable and increasingly brittle hacks.
> > 
> > Let's just rip out all the madness and start over. We can re-architect
> > this based on having a separate standalone setup_data file, which is how
> > it should have been done in the first place. This is a larger project
> > with a few things to coordinate, but we can't really begin thinking
> > about that while trying to play whack-a-mole with the current buggy
> > implementation.
> > 
> > So this commit removes the setup_data setting from x86_load_linux(),
> > while leaving intact the infrastructure we'll need in the future to try
> > again.
> > 
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Cc: Dov Murik <dovmurik@linux.ibm.com>
> > Cc: Tom Lendacky <thomas.lendacky@amd.com>
> > Cc: Gerd Hoffmann <kraxel@redhat.com>
> > Cc: Daniel P. Berrangé <berrange@redhat.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Richard Henderson <richard.henderson@linaro.org>
> > Cc: H. Peter Anvin <hpa@zytor.com>
> > Cc: Philippe Mathieu-Daudé <philmd@linaro.org>
> > Cc: Nathan Chancellor <nathan@kernel.org>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: Eric Biggers <ebiggers@kernel.org>
> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> 
> Thanks for the quick patch! Both of my use cases appear fixed.
> 
> Tested-by: Nathan Chancellor <nathan@kernel.org>

Unfortunately, I only tested qemu-system-x86_64 booting via EFI and just now 
came to
find out this breaks booting without EFI in both qemu-system-i386 and
qemu-system-x86_64 (just defconfig for both images):

$ qemu-system-i386 \
    -d unimp,guest_errors \
    -kernel arch/x86/boot/bzImage \
    -append "console=ttyS0 earlycon=uart8250,io,0x3f8" \
    -cpu host \
    -enable-kvm \
    -smp 8 \
    -display none \
    -initrd .../boot-utils-ro/images/x86/rootfs.cpio \
    -m 512m \
    -nodefaults \
    -no-reboot \
    -serial mon:stdio

There is no output, which I suppose makes sense since we are very early
in boot. Sorry for missing this initially, I'll ramp up my testing for
future patches.

Cheers,
Nathan

> > ---
> >  hw/i386/microvm.c |  15 ++----
> >  hw/i386/x86.c     | 120 +++++-----------------------------------------
> >  2 files changed, 17 insertions(+), 118 deletions(-)
> > 
> > diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
> > index 29f30dd6d3..170a331e3f 100644
> > --- a/hw/i386/microvm.c
> > +++ b/hw/i386/microvm.c
> > @@ -378,8 +378,7 @@ static void microvm_fix_kernel_cmdline(MachineState 
> > *machine)
> >      MicrovmMachineState *mms = MICROVM_MACHINE(machine);
> >      BusState *bus;
> >      BusChild *kid;
> > -    char *cmdline, *existing_cmdline;
> > -    size_t len;
> > +    char *cmdline;
> >  
> >      /*
> >       * Find MMIO transports with attached devices, and add them to the 
> > kernel
> > @@ -388,8 +387,7 @@ static void microvm_fix_kernel_cmdline(MachineState 
> > *machine)
> >       * Yes, this is a hack, but one that heavily improves the UX without
> >       * introducing any significant issues.
> >       */
> > -    existing_cmdline = fw_cfg_read_bytes_ptr(x86ms->fw_cfg, 
> > FW_CFG_CMDLINE_DATA);
> > -    cmdline = g_strdup(existing_cmdline);
> > +    cmdline = g_strdup(machine->kernel_cmdline);
> >      bus = sysbus_get_default();
> >      QTAILQ_FOREACH(kid, &bus->children, sibling) {
> >          DeviceState *dev = kid->child;
> > @@ -413,12 +411,9 @@ static void microvm_fix_kernel_cmdline(MachineState 
> > *machine)
> >          }
> >      }
> >  
> > -    len = strlen(cmdline);
> > -    if (len > VIRTIO_CMDLINE_TOTAL_MAX_LEN + strlen(existing_cmdline)) {
> > -        fprintf(stderr, "qemu: virtio mmio cmdline too large, skipping\n");
> > -    } else {
> > -        memcpy(existing_cmdline, cmdline, len + 1);
> > -    }
> > +    fw_cfg_modify_i32(x86ms->fw_cfg, FW_CFG_CMDLINE_SIZE, strlen(cmdline) 
> > + 1);
> > +    fw_cfg_modify_string(x86ms->fw_cfg, FW_CFG_CMDLINE_DATA, cmdline);
> > +
> >      g_free(cmdline);
> >  }
> >  
> > diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> > index eaff4227bd..6cfdca9acd 100644
> > --- a/hw/i386/x86.c
> > +++ b/hw/i386/x86.c
> > @@ -50,7 +50,6 @@
> >  #include "hw/intc/i8259.h"
> >  #include "hw/rtc/mc146818rtc.h"
> >  #include "target/i386/sev.h"
> > -#include "hw/i386/microvm.h"
> >  
> >  #include "hw/acpi/cpu_hotplug.h"
> >  #include "hw/irq.h"
> > @@ -770,30 +769,6 @@ static bool load_elfboot(const char *kernel_filename,
> >      return true;
> >  }
> >  
> > -typedef struct SetupDataFixup {
> > -    void *pos;
> > -    hwaddr orig_val, new_val;
> > -    uint32_t addr;
> > -} SetupDataFixup;
> > -
> > -static void fixup_setup_data(void *opaque)
> > -{
> > -    SetupDataFixup *fixup = opaque;
> > -    stq_p(fixup->pos, fixup->new_val);
> > -}
> > -
> > -static void reset_setup_data(void *opaque)
> > -{
> > -    SetupDataFixup *fixup = opaque;
> > -    stq_p(fixup->pos, fixup->orig_val);
> > -}
> > -
> > -static void reset_rng_seed(void *opaque)
> > -{
> > -    SetupData *setup_data = opaque;
> > -    qemu_guest_getrandom_nofail(setup_data->data, 
> > le32_to_cpu(setup_data->len));
> > -}
> > -
> >  void x86_load_linux(X86MachineState *x86ms,
> >                      FWCfgState *fw_cfg,
> >                      int acpi_data_size,
> > @@ -803,29 +778,20 @@ void x86_load_linux(X86MachineState *x86ms,
> >      bool linuxboot_dma_enabled = 
> > X86_MACHINE_GET_CLASS(x86ms)->fwcfg_dma_enabled;
> >      uint16_t protocol;
> >      int setup_size, kernel_size, cmdline_size;
> > -    int dtb_size, setup_data_offset;
> >      uint32_t initrd_max;
> >      uint8_t header[8192], *setup, *kernel;
> > -    hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0, 
> > first_setup_data = 0;
> > +    hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0;
> >      FILE *f;
> >      char *vmode;
> >      MachineState *machine = MACHINE(x86ms);
> > -    SetupData *setup_data;
> >      const char *kernel_filename = machine->kernel_filename;
> >      const char *initrd_filename = machine->initrd_filename;
> > -    const char *dtb_filename = machine->dtb;
> > -    char *kernel_cmdline;
> > +    const char *kernel_cmdline = machine->kernel_cmdline;
> >      SevKernelLoaderContext sev_load_ctx = {};
> >      enum { RNG_SEED_LENGTH = 32 };
> >  
> > -    /*
> > -     * Add the NUL terminator, some padding for the microvm cmdline 
> > fiddling
> > -     * hack, and then align to 16 bytes as a paranoia measure
> > -     */
> > -    cmdline_size = (strlen(machine->kernel_cmdline) + 1 +
> > -                    VIRTIO_CMDLINE_TOTAL_MAX_LEN + 16) & ~15;
> > -    /* Make a copy, since we might append arbitrary bytes to it later. */
> > -    kernel_cmdline = g_strndup(machine->kernel_cmdline, cmdline_size);
> > +    /* Align to 16 bytes as a paranoia measure */
> > +    cmdline_size = (strlen(kernel_cmdline) + 16) & ~15;
> >  
> >      /* load the kernel header */
> >      f = fopen(kernel_filename, "rb");
> > @@ -966,6 +932,12 @@ void x86_load_linux(X86MachineState *x86ms,
> >          initrd_max = x86ms->below_4g_mem_size - acpi_data_size - 1;
> >      }
> >  
> > +    fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_ADDR, cmdline_addr);
> > +    fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_SIZE, strlen(kernel_cmdline) + 
> > 1);
> > +    fw_cfg_add_string(fw_cfg, FW_CFG_CMDLINE_DATA, kernel_cmdline);
> > +    sev_load_ctx.cmdline_data = (char *)kernel_cmdline;
> > +    sev_load_ctx.cmdline_size = strlen(kernel_cmdline) + 1;
> > +
> >      if (protocol >= 0x202) {
> >          stl_p(header + 0x228, cmdline_addr);
> >      } else {
> > @@ -1078,81 +1050,13 @@ void x86_load_linux(X86MachineState *x86ms,
> >      }
> >      fclose(f);
> >  
> > -    /* append dtb to kernel */
> > -    if (dtb_filename) {
> > -        if (protocol < 0x209) {
> > -            fprintf(stderr, "qemu: Linux kernel too old to load a dtb\n");
> > -            exit(1);
> > -        }
> > -
> > -        dtb_size = get_image_size(dtb_filename);
> > -        if (dtb_size <= 0) {
> > -            fprintf(stderr, "qemu: error reading dtb %s: %s\n",
> > -                    dtb_filename, strerror(errno));
> > -            exit(1);
> > -        }
> > -
> > -        setup_data_offset = cmdline_size;
> > -        cmdline_size += sizeof(SetupData) + dtb_size;
> > -        kernel_cmdline = g_realloc(kernel_cmdline, cmdline_size);
> > -        setup_data = (void *)kernel_cmdline + setup_data_offset;
> > -        setup_data->next = cpu_to_le64(first_setup_data);
> > -        first_setup_data = cmdline_addr + setup_data_offset;
> > -        setup_data->type = cpu_to_le32(SETUP_DTB);
> > -        setup_data->len = cpu_to_le32(dtb_size);
> > -        load_image_size(dtb_filename, setup_data->data, dtb_size);
> > -    }
> > -
> > -    if (!legacy_no_rng_seed && protocol >= 0x209) {
> > -        setup_data_offset = cmdline_size;
> > -        cmdline_size += sizeof(SetupData) + RNG_SEED_LENGTH;
> > -        kernel_cmdline = g_realloc(kernel_cmdline, cmdline_size);
> > -        setup_data = (void *)kernel_cmdline + setup_data_offset;
> > -        setup_data->next = cpu_to_le64(first_setup_data);
> > -        first_setup_data = cmdline_addr + setup_data_offset;
> > -        setup_data->type = cpu_to_le32(SETUP_RNG_SEED);
> > -        setup_data->len = cpu_to_le32(RNG_SEED_LENGTH);
> > -        qemu_guest_getrandom_nofail(setup_data->data, RNG_SEED_LENGTH);
> > -        qemu_register_reset_nosnapshotload(reset_rng_seed, setup_data);
> > -        fw_cfg_add_bytes_callback(fw_cfg, FW_CFG_KERNEL_DATA, 
> > reset_rng_seed, NULL,
> > -                                  setup_data, kernel, kernel_size, true);
> > -    } else {
> > -        fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, kernel_size);
> > -    }
> > -
> > -    fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_ADDR, cmdline_addr);
> > -    fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_SIZE, cmdline_size);
> > -    fw_cfg_add_bytes(fw_cfg, FW_CFG_CMDLINE_DATA, kernel_cmdline, 
> > cmdline_size);
> > -    sev_load_ctx.cmdline_data = (char *)kernel_cmdline;
> > -    sev_load_ctx.cmdline_size = cmdline_size;
> > -
> > +    fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, kernel_size);
> >      fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, prot_addr);
> >      fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, kernel_size);
> >      sev_load_ctx.kernel_data = (char *)kernel;
> >      sev_load_ctx.kernel_size = kernel_size;
> >  
> > -    /*
> > -     * If we're starting an encrypted VM, it will be OVMF based, which 
> > uses the
> > -     * efi stub for booting and doesn't require any values to be placed in 
> > the
> > -     * kernel header.  We therefore don't update the header so the hash of 
> > the
> > -     * kernel on the other side of the fw_cfg interface matches the hash 
> > of the
> > -     * file the user passed in.
> > -     */
> > -    if (!sev_enabled() && first_setup_data) {
> > -        SetupDataFixup *fixup = g_malloc(sizeof(*fixup));
> > -
> > -        memcpy(setup, header, MIN(sizeof(header), setup_size));
> > -        /* Offset 0x250 is a pointer to the first setup_data link. */
> > -        fixup->pos = setup + 0x250;
> > -        fixup->orig_val = ldq_p(fixup->pos);
> > -        fixup->new_val = first_setup_data;
> > -        fixup->addr = cpu_to_le32(real_addr);
> > -        fw_cfg_add_bytes_callback(fw_cfg, FW_CFG_SETUP_ADDR, 
> > fixup_setup_data, NULL,
> > -                                  fixup, &fixup->addr, 
> > sizeof(fixup->addr), true);
> > -        qemu_register_reset(reset_setup_data, fixup);
> > -    } else {
> > -        fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_ADDR, real_addr);
> > -    }
> > +    fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_ADDR, real_addr);
> >      fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_SIZE, setup_size);
> >      fw_cfg_add_bytes(fw_cfg, FW_CFG_SETUP_DATA, setup, setup_size);
> >      sev_load_ctx.setup_data = (char *)setup;
> > -- 
> > 2.39.1
> >