[Etherboot-users] Via RNG xstore in Etherboot

[Robert H. <rob...@ya...>]

Hi all,

OK this question may be a bit obscure, but I hope
someone might have some insight as to what is going
on...

I am trying to call the Via RNG (xstore instruction)
from etherboot, and my platform resets every time I
call it.

I have copied the xstore asm() code from the
hw_random.c driver in Linux. I have made sure the Via
MSR 0x110b is set up correctly. I've checked that the
assembler and byte code looks OK (the same as the
hwrandom driver), but I still get the reset.

Do I have to set something else up on the processor,
or call xstore in a different way?

Thanks,

Robert

The following is the code I am using showing the MSR
initialization and the xstore call. Though the first
read of the MSR indicates that the RNG is enabled by
default anyway. It is pretty much a straight copy from
hw_random.c.

#define MSR_VIA_RNG 0x110b
enum {
    VIA_STRFILT_CNT_SHIFT = 16,
    VIA_STRFILT_FAIL = (1 << 15),
    VIA_STRFILT_ENABLE = (1 << 14),
    VIA_RAWBITS_ENABLE = (1 << 13),
    VIA_RNG_ENABLE = (1 << 6),
    VIA_XSTORE_CNT_MASK = 0x0F,

    VIA_RNG_CHUNK_8 = 0x00, /* 64 rand bits, 64 stored
bits */
    VIA_RNG_CHUNK_4 = 0x01, /* 32 rand bits, 32 stored
bits */
    VIA_RNG_CHUNK_4_MASK = 0xFFFFFFFF,
    VIA_RNG_CHUNK_2 = 0x02, /* 16 rand bits, 32 stored
bits */
    VIA_RNG_CHUNK_2_MASK = 0xFFFF,
    VIA_RNG_CHUNK_1 = 0x03, /* 8 rand bits, 32 stored
bits */

    VIA_RNG_CHUNK_1_MASK = 0xFF,
};

#define rdmsr(msr,val1,val2) \
    __asm__ __volatile__("rdmsr" \
        : "=a" (val1), "=d" (val2) \
        : "c" (msr))

#define wrmsr(msr,val1,val2) \
    __asm__ __volatile__("wrmsr" \
        : /* no outputs */ \
        : "c" (msr), "a" (val1), "d" (val2))

static int via_RNGinit( void )
{
    u32 lo, hi, old_lo;

    printf( "VIA init\n" );
    rdmsr(MSR_VIA_RNG, lo, hi);
    printf( "lo = %#x, hi = %#x\n", lo, hi );

    old_lo = lo;
    lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT);
    lo &= ~VIA_XSTORE_CNT_MASK;
    lo |= (VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL |
VIA_RAWBITS_ENABLE);
    lo |= VIA_RNG_ENABLE;
    lo |= ( 0x3 << 8 );

    if (lo != old_lo)
        wrmsr(MSR_VIA_RNG, lo, hi);

    rdmsr(MSR_VIA_RNG, lo, hi);
    printf( "lo = %#x, hi = %#x\n", lo, hi );
    if ((lo & VIA_RNG_ENABLE) == 0) {
        printf( "cannot enable VIA C3 RNG,
aborting\n");
        return -1;
    }

    printf( "Done!\n" );

    return 0;
}

static inline u32 xstore(u32 *addr, u32 edx_in)
{
    u32 eax_out;

    asm volatile (".byte 0x0f,0xa7,0xc0 /* xstore
%%edi (addr=%0) */"
        : "=a"(eax_out), "=m"(*addr)
        : "D"(addr), "d"(edx_in));

    return eax_out;
}



		
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