Hi Marc,
On 14/03/18 16:50, Marc Zyngier wrote:
> So far, we're using a complicated sequence of alternatives to
> patch the kernel/hyp VA mask on non-VHE, and NOP out the
> masking altogether when on VHE.
>
> The newly introduced dynamic patching gives us the opportunity
> to simplify that code by patching a single instruction with
> the correct mask (instead of the mind bending cummulative masking
(Nit: cumulative)
(so this series removes mind bending code?)
> we have at the moment) or even a single NOP on VHE. This also
> adds some initial code that will allow the patching callback
> to switch to a more complex patching.
> diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
> new file mode 100644
> index 000000000000..45e7802328d4
> --- /dev/null
> +++ b/arch/arm64/kvm/va_layout.c
> +void __init kvm_update_va_mask(struct alt_instr *alt,
> + __le32 *origptr, __le32 *updptr, int nr_inst)
> +{
> + int i;
> +
> + /* We only expect a single instruction in the alternative sequence */
> + BUG_ON(nr_inst != 1);
> +
> + if (!has_vhe() && !va_mask)
> + compute_layout();
> +
> + for (i = 0; i < nr_inst; i++) {
> + u32 rd, rn, insn, oinsn;
> +
> + /*
> + * VHE doesn't need any address translation, let's NOP
> + * everything.
> + */
> + if (has_vhe()) {
> + updptr[i] = aarch64_insn_gen_nop();
cpu_to_le32()? (I'm not going to try an boot a BE VHE model...)
aarch64_insn_gen_nop() returns:
| aarch64_insn_get_hint_value() | AARCH64_INSN_HINT_NOP;
It doesn't look like these aarch64_insn_get_XXX_value() helpers are forcing a
particular endianness. ftrace uses this, via ftrace_modify_code() ->
aarch64_insn_patch_text_nosync() -> aarch64_insn_write(), which does:
| return __aarch64_insn_write(addr, cpu_to_le32(insn));
So it looks like the conversion is required. Patch 16 looks fine for this.
(and, I ran the teardown code on Juno big-endian...)
> + continue;
> + }
> +
> + oinsn = le32_to_cpu(origptr[i]);
> + rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD,
> oinsn);
> + rn = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RN,
> oinsn);
> +
> + insn = compute_instruction(i, rd, rn);
> + BUG_ON(insn == AARCH64_BREAK_FAULT);
> +
> + updptr[i] = cpu_to_le32(insn);
> + }
> +}
With that,
Reviewed-by: James Morse <[email protected]>
Thanks,
James
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