Re: [SeaBIOS] [PATCH RFC 5/7] Add PMM memory allocation facilities for VGA option ROMs

[Mark Marshall]

Hi.

This patch series looks very interesting to me.
This patch has been dropped from the V2 series?

According to the bits of the PCI spec that I can find, 
the option ROM is copied into RAM which is left read-write 
while the initialisation vector is called, and the RAM is 
then set to read-only after this time.  Does your VGA option 
ROM use this feature?  Do you know of any other's that do?  
(This is in the V2.1 and V3.0 PCI spec's.  Also in at least 
the V3.0 PCI spec is says that the initialisation code is 
run in "big real mode", with 4G segments, do you know of 
any code that uses this feature?).

(I understand that you might be using PMM memory because 
you want read-write memory at run time, so my comments 
might not be of help, but you could at least store the 
pointer to your block in the ROM.  I have found some BIOSs
that do modify the ROM image in this way (another common 
thing to store is the PCI BDF of the device, and the BAR 
locations).)

Thanks for the good work,

MM

PS.
I'm interested in this because I wrote the OGP VGA BIOS 
(in 16-bit x86 ASM), a while ago now.  A choice made for 
two reasons really: 1, I hadn't found SeaBIOS (And didn't 
know quite how well you could get gcc to produce 16-bit 
code), and 2, I really wanted to write a chunk of 16-bit 
assembler (this was a hobby, not work, so I felt I could 
make a crazy choice like that and get away with it).

If I get a free afternoon, I will try to convert that code 
to use the SeaBIOS VGA framework.  It's interesting to note
that we have both implemented features that are not in the 
other's BIOS.
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]]
> On Behalf Of Julian Pidancet
> Sent: 16 December 2011 14:15
> To: [e-mail]
> Cc: Julian Pidancet
> Subject: [SeaBIOS] [PATCH RFC 5/7] Add PMM memory allocation facilities
> for VGA option ROMs
>
> This patch implements a way for option ROMs to allocate some space
> using the bios PMM interface.
>
> Since the VGA option ROM is placed in read only memory, the only way to
> get memory to store global variables is either use the EBDA, or use the
> PMM if the BIOS supports it.
>
> This simple patchs adds only pmm_scan and pmm_allocate. The first one
> is used to scan the memory and find the PMM entry point, the second one
> is used to request the BIOS to allocate blocks of memory.
>
> The pmm_find and pmm_deallocate functions are yet to be implemented.
>
> Signed-off-by: Julian Pidancet <[e-mail]>
> ---
>  Makefile     |    2 +-
>  vgasrc/pmm.c |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  vgasrc/pmm.h |   16 ++++++++++++++++
>  3 files changed, 67 insertions(+), 1 deletions(-)  create mode 100644
> vgasrc/pmm.c  create mode 100644 vgasrc/pmm.h
>
> diff --git a/Makefile b/Makefile
> index cb00958..1b8ba60 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -171,7 +171,7 @@ $(OUT)bios.bin.elf $(OUT)bios.bin: $(OUT)rom.o
> tools/checkrom.py
>
> # VGA src files
>  SRCVGA=src/output.c src/util.c vgasrc/vga.c vgasrc/vgafb.c
> vgasrc/vgaio.c \
> -       vgasrc/vgatables.c vgasrc/vgafonts.c vgasrc/clext.c
> +       vgasrc/vgatables.c vgasrc/vgafonts.c vgasrc/clext.c
> vgasrc/pmm.c
>
> $(OUT)vgaccode.16.s: $(OUT)autoconf.h ; $(call whole-compile,
> $(CFLAGS16) -S -Isrc, $(SRCVGA),$@)
>
> diff --git a/vgasrc/pmm.c b/vgasrc/pmm.c new file mode 100644 index
> 0000000..1732149
> --- /dev/null
> +++ b/vgasrc/pmm.c
> @@ -0,0 +1,50 @@
> +#include "biosvar.h" // GET_GLOBAL
> +#include "util.h" // memset
> +
> +#define PMM_SIGNATURE 0x4d4d5024 // $PMM
> +
> +struct pmmheader {
> +    u32 signature;
> +    u8 version;
> +    u8 length;
> +    u8 checksum;
> +    u16 entry_offset;
> +    u16 entry_seg;
> +    u8 reserved[5];
> +} PACKED;
> +
> +u32 pmm_allocate(u16 seg, u32 length, u32 handle, u16 flags) {
> +    u16 ax, dx;
> +
> +    asm volatile ("movw %2, %%es\n"
> +                  "pushw %3\n"
> +                  "pushl %4\n"
> +                  "pushl %5\n"
> +                  "pushw $0x0\n" /* PMM_ALLOCATE */
> +                  "lcallw *%%es:7\n"
> +                  "addw $12, %%sp\n"
> +                  : "=a"(ax), "=d"(dx)
> +                  : "r"(seg), "r"(flags), "r"(handle), "r"(length)
> +                  : "cc", "memory");
> +
> +    return (dx << 16) | ax;
> +}
> +
> +u16 pmm_scan(void)
> +{
> +    u16 seg;
> +    struct pmmheader *hdr = (struct pmmheader *)0;
> +
> +    for (seg = 0xe000; seg; seg++) {
> +        u32 val = GET_FARVAR(seg, hdr->signature);
> +
> +        if (val == PMM_SIGNATURE &&
> +            !checksum_far(seg, hdr, GET_FARVAR(seg, hdr->length))) {
> +            return seg;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> diff --git a/vgasrc/pmm.h b/vgasrc/pmm.h new file mode 100644 index
> 0000000..f6479ad
> --- /dev/null
> +++ b/vgasrc/pmm.h
> @@ -0,0 +1,16 @@
> +#include "biosvar.h" // GET_GLOBAL
> +#include "util.h" // memset
> +
> +#define PMM_MEMORY_TYPE_INVALID    (0 << 0)
> +#define PMM_MEMORY_TYPE_CONVENTION (1 << 0)
> +#define PMM_MEMORY_TYPE_EXTENDED   (2 << 0)
> +
> +#define PMM_BLOCK_NOT_ALIGNED      (0 << 2)
> +#define PMM_BLOCK_ALIGNED          (1 << 2)
> +
> +/* Only in PCI FW spec: */
> +#define PMM_MEMORY_ATTR_TEMPORARY  (0 << 3) #define
> +PMM_MEMORY_ATTR_PERMANENT  (1 << 3)
> +
> +u32 pmm_allocate(u16 seg, u32 length, u32 handle, u16 flags);
> +u16 pmm_scan(void);
> --
> Julian Pidancet
>
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