Re: [PATCH] x86: temporarily remove all attempts to provide setup_data
From: Nathan Chancellor
Date: Wed Feb 08 2023 - 14:10:39 EST
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@xxxxxxxxxx>
> > Cc: Dov Murik <dovmurik@xxxxxxxxxxxxx>
> > Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> > Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> > Cc: Daniel P. Berrangé <berrange@xxxxxxxxxx>
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: Richard Henderson <richard.henderson@xxxxxxxxxx>
> > Cc: H. Peter Anvin <hpa@xxxxxxxxx>
> > Cc: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
> > Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
> > Cc: Borislav Petkov <bp@xxxxxxxxx>
> > Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
> > Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
>
> Thanks for the quick patch! Both of my use cases appear fixed.
>
> Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
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
> >