[SeaBIOS] [PATCH v3 2/2] Boot Linux using QEMU fw_cfg DMA interface
Marc Marí
markmb at redhat.com
Fri Sep 18 19:28:57 CET 2015
On Fri, 18 Sep 2015 14:40:30 -0400
"Kevin O'Connor" <kevin at koconnor.net> wrote:
> On Fri, Sep 18, 2015 at 10:59:15AM +0200, Marc Marí wrote:
> > Reading Linux from the fw_cfg interface is faster using the DMA
> > interface. For this reason, add a Linux loader that can benefit
> > from this interface.
> >
> > Signed-off-by: Marc Marí <markmb at redhat.com>
> > ---
> > src/boot.c | 32 ++++++++++++++++-----
> > src/fw/paravirt.c | 85
> > ++++++++++++++++++++++++++++++++++++++++++++-----------
> > src/fw/paravirt.h | 36 +++++++++++++++++++++++ src/post.c |
> > 1 + src/romlayout.S | 20 +++++++++++++
> > src/util.h | 1 +
> > 6 files changed, 152 insertions(+), 23 deletions(-)
> >
> > diff --git a/src/boot.c b/src/boot.c
> > index e0f73a3..52918f8 100644
> > --- a/src/boot.c
> > +++ b/src/boot.c
> > @@ -300,13 +300,14 @@ struct bootentry_s {
> > };
> > static struct hlist_head BootList VARVERIFY32INIT;
> >
> > -#define IPL_TYPE_FLOPPY 0x01
> > -#define IPL_TYPE_HARDDISK 0x02
> > -#define IPL_TYPE_CDROM 0x03
> > -#define IPL_TYPE_CBFS 0x20
> > -#define IPL_TYPE_BEV 0x80
> > -#define IPL_TYPE_BCV 0x81
> > -#define IPL_TYPE_HALT 0xf0
> > +#define IPL_TYPE_FLOPPY 0x01
> > +#define IPL_TYPE_HARDDISK 0x02
> > +#define IPL_TYPE_CDROM 0x03
> > +#define IPL_TYPE_CBFS 0x20
> > +#define IPL_TYPE_QEMU_VMLINUX 0x21
> > +#define IPL_TYPE_BEV 0x80
> > +#define IPL_TYPE_BCV 0x81
> > +#define IPL_TYPE_HALT 0xf0
> >
> > static void
> > bootentry_add(int type, int prio, u32 data, const char *desc)
> > @@ -398,6 +399,12 @@ boot_add_cbfs(void *data, const char *desc,
> > int prio) bootentry_add(IPL_TYPE_CBFS, defPrio(prio, DEFAULT_PRIO),
> > (u32)data, desc); }
> >
> > +// Add a FW_CFG DMA boot
> > +void
> > +boot_add_qemu_vmlinux(const char *desc, int prio)
> > +{
> > + bootentry_add(IPL_TYPE_QEMU_VMLINUX, defPrio(prio,
> > DEFAULT_PRIO), 0, desc); +}
> >
> > /****************************************************************
> > * Keyboard calls
> > @@ -684,6 +691,14 @@ boot_rom(u32 vector)
> > call_boot_entry(so, 0);
> > }
> >
> > +// Boot from a linuxboot ROM when QEMU cfg is in DMA mode
> > +static void
> > +boot_qemu_vmlinux_dma(void)
> > +{
> > + printf("Booting Linux from fw_cfg...\n");
> > + qemu_vmlinux_dma_boot();
> > +}
> > +
> > // Unable to find bootable device - warn user and eventually retry.
> > static void
> > boot_fail(void)
> > @@ -734,6 +749,9 @@ do_boot(int seq_nr)
> > case IPL_TYPE_BEV:
> > boot_rom(ie->vector);
> > break;
> > + case IPL_TYPE_QEMU_VMLINUX:
> > + boot_qemu_vmlinux_dma();
> > + break;
> > case IPL_TYPE_HALT:
> > boot_fail();
> > break;
> > diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
> > index 65f9fba..6896511 100644
> > --- a/src/fw/paravirt.c
> > +++ b/src/fw/paravirt.c
> > @@ -23,7 +23,8 @@
> > #include "util.h" // pci_setup
> > #include "x86.h" // cpuid
> > #include "xen.h" // xen_biostable_setup
> > -#include "stacks.h" // yield
> > +#include "bregs.h" // struct bregs
> > +#include "stacks.h" // farcall16big, yield
> >
> > // Amount of continuous ram under 4Gig
> > u32 RamSize;
> > @@ -185,21 +186,6 @@ qemu_platform_setup(void)
> > * QEMU firmware config (fw_cfg) interface
> > ****************************************************************/
> >
> > -// List of QEMU fw_cfg entries. DO NOT ADD MORE. (All new content
> > -// should be passed via the fw_cfg "file" interface.)
> > -#define QEMU_CFG_SIGNATURE 0x00
> > -#define QEMU_CFG_ID 0x01
> > -#define QEMU_CFG_UUID 0x02
> > -#define QEMU_CFG_NUMA 0x0d
> > -#define QEMU_CFG_BOOT_MENU 0x0e
> > -#define QEMU_CFG_MAX_CPUS 0x0f
> > -#define QEMU_CFG_FILE_DIR 0x19
> > -#define QEMU_CFG_ARCH_LOCAL 0x8000
> > -#define QEMU_CFG_ACPI_TABLES (QEMU_CFG_ARCH_LOCAL + 0)
> > -#define QEMU_CFG_SMBIOS_ENTRIES (QEMU_CFG_ARCH_LOCAL + 1)
> > -#define QEMU_CFG_IRQ0_OVERRIDE (QEMU_CFG_ARCH_LOCAL + 2)
> > -#define QEMU_CFG_E820_TABLE (QEMU_CFG_ARCH_LOCAL + 3)
> > -
> > static void
> > qemu_cfg_select(u16 f)
> > {
> > @@ -509,3 +495,70 @@ void qemu_cfg_init(void)
> > dprintf(1, "Moving pm_base to 0x%x\n", acpi_pm_base);
> > }
> > }
> > +
> > +void qemu_vmlinux_dma_boot(void)
> > +{
> > + dprintf(1, "Loading kernel\n");
> > +
> > + irq_disable();
>
> SeaBIOS always disabled interrupts in C code (see
> http://www.seabios.org/Execution_and_code_flow#Hardware_interrupts ),
> so this irq_disable() is not needed.
>
> > +
> > + void *setup_addr;
> > + u32 setup_size;
> > + qemu_cfg_read_entry(&setup_addr, QEMU_CFG_SETUP_ADDR, 4);
> > + qemu_cfg_read_entry(&setup_size, QEMU_CFG_SETUP_SIZE, 4);
> > + qemu_cfg_read_entry(setup_addr, QEMU_CFG_SETUP_DATA,
> > setup_size); +
> > + u16 protocol = readw(setup_addr + 0x206);
> > + if (protocol < 0x203) {
> > + /* Assume initrd_max 0x37ffffff */
> > + writel(setup_addr + 0x22c, 0x37ffffff);
> > + }
> > +
> > + void *initrd_addr;
> > + u32 initrd_size;
> > + qemu_cfg_read_entry(&initrd_addr, QEMU_CFG_INITRD_ADDR, 4);
> > + qemu_cfg_read_entry(&initrd_size, QEMU_CFG_INITRD_SIZE, 4);
> > +
> > + u32 initrd_end_page = (u32)(initrd_addr + initrd_size) & -4096;
> > + u32 max_allowed_page = readl(setup_addr + 0x22c) & -4096;
>
> Use of the ALIGN_DOWN() macro would be preferable here.
>
> > + if (initrd_end_page != max_allowed_page) {
> > + /* Initrd at the end of memory. Compute better initrd
> > address
> > + * based on e801 data
> > + */
> > + initrd_addr = (void *)((LegacyRamSize - initrd_size) &
> > -4096);
> > + writel(setup_addr + 0x218, (u32)initrd_addr);
> > + }
> > +
> > + qemu_cfg_read_entry(initrd_addr, QEMU_CFG_INITRD_DATA,
> > initrd_size); +
> > + void *kernel_addr;
> > + u32 kernel_size;
> > + qemu_cfg_read_entry(&kernel_addr, QEMU_CFG_KERNEL_ADDR, 4);
> > + qemu_cfg_read_entry(&kernel_size, QEMU_CFG_KERNEL_SIZE, 4);
> > + qemu_cfg_read_entry(kernel_addr, QEMU_CFG_KERNEL_DATA,
> > kernel_size); +
> > + void *cmdline_addr;
> > + u32 cmdline_size;
> > + qemu_cfg_read_entry(&cmdline_addr, QEMU_CFG_CMDLINE_ADDR, 4);
> > + qemu_cfg_read_entry(&cmdline_size, QEMU_CFG_CMDLINE_SIZE, 4);
> > + qemu_cfg_read_entry(cmdline_addr, QEMU_CFG_CMDLINE_DATA,
> > cmdline_size); +
> > + dprintf(1, "Jumping to kernel %d@%x %d@%x %d@%x %d@%x\n"
> > + , setup_size, (u32)setup_addr, cmdline_size,
> > (u32)cmdline_addr
> > + , kernel_size, (u32)kernel_addr, initrd_size,
> > (u32)initrd_addr);
> > + struct bregs br;
> > + memset(&br, 0, sizeof(br));
> > + extern void kernel_stub(void);
> > + br.ebx = (u32)setup_addr >> 4;
> > + br.edx = (u32)cmdline_addr - (u32)setup_addr - 16;
> > + br.code = SEGOFF(SEG_BIOS, (u32)kernel_stub - BUILD_BIOS_ADDR);
> > +
> > + farcall16big(&br);
> > +}
> > +
> > +void qemu_vmlinux_dma_setup(void) {
> > + if (qemu_cfg_dma_enabled()) {
>
> I don't think this feature should depend on DMA (it works fine even if
> fw_cfg DMA is not available). I also don't think "dma" should be in
> the function names - qemu_vmlinux_setup() is fine.
>
> Also, the code should check if there is a kernel before registering an
> IPL - for example:
>
> u32 kernel_size;
> qemu_cfg_read_entry(&kernel_size, QEMU_CFG_KERNEL_SIZE,
> sizeof(kernel_size)); if (!kernel_size)
> return;
>
> > + boot_add_qemu_vmlinux("QEMU Kernel image",
> > +
> > bootprio_find_named_rom("genroms/linuxboot.bin", 0));
>
> Using "genroms/linuxboot.bin" works for testing, but I think a new
> bootorder id (eg, "vmlinux") will need to be defined between QEMU and
> SeaBIOS. I don't think it would be good to overload the meaning of
> the "genroms/" prefix.
I was looking at it, but I don't see a "good" way to put it.
If you want to boot from fw_cfg through linuxboot.S, you prefer to boot
using fw_cfg DMA, which is faster. And adding a new entry would mean
adding a new type (?) which would be added in the same cases as
linuxboot.S. It looks a lot of work for a thing that is repeated.
But yes, it's really ugly to overload it in this way.
Any other ideas?
Marc
> Otherwise the series looks good to me. Once the QEMU series is
> committed we can commit this series to SeaBIOS.
>
> -Kevin
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