Hi James,
On 04/06/2019 15:45, James Morse wrote:
> The EL2 vector hardening feature causes KVM to generate vectors for
> each type of CPU present in the system. The generated sequences already
> do some of the early guest-exit work (i.e. saving registers). To avoid
> duplication the generated vectors branch to the original vector just
> after the preamble. This size is hard coded.
>
> Adding new instructions to the HYP vector causes strange side effects,
> which are difficult to debug as the affected code is patched in at
> runtime.
>
> Add KVM_VECTOR_PREAMBLE to tell kvm_patch_vector_branch() how big
> the preamble is. The valid_vect macro can then validate this at
> build time.
>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> ---
> arch/arm64/include/asm/kvm_asm.h | 6 ++++++
> arch/arm64/kvm/hyp/hyp-entry.S | 10 +++++++++-
> arch/arm64/kvm/va_layout.c | 7 +++----
> 3 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index ff73f5462aca..9170c43b332f 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -41,6 +41,12 @@
> {ARM_EXCEPTION_TRAP, "TRAP" }, \
> {ARM_EXCEPTION_HYP_GONE, "HYP_GONE" }
>
> +/*
> + * Size of the HYP vectors preamble. kvm_patch_vector_branch() generates code
> + * that jumps over this.
> + */
> +#define KVM_VECTOR_PREAMBLE 4
Nit: I would use AARCH64_INSN_SIZE instead of 4 for the value if
possible. Makes it clear what the value of the vectore preamble
represent (and if we ad instruction we just multiply).
Otherwise the patch seems a good improvement.
Reviewed-by: Julien Thierry <julien.thierry@xxxxxxx>
Thanks,
--
Julien Thierry
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