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SubjectRe: [PATCH v4 15/26] kvm: arm64: Add SMC handler in nVHE EL2
On 2020-12-02 18:41, David Brazdil wrote:
> Add handler of host SMCs in KVM nVHE trap handler. Forward all SMCs to
> EL3 and propagate the result back to EL1. This is done in preparation
> for validating host SMCs in KVM protected mode.
>
> The implementation assumes that firmware uses SMCCC v1.2 or older. That
> means x0-x17 can be used both for arguments and results, other GPRs are
> preserved.
>
> Signed-off-by: David Brazdil <dbrazdil@google.com>
> ---
> arch/arm64/kvm/hyp/nvhe/host.S | 38 ++++++++++++++++++++++++++++++
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 35 ++++++++++++++++++++++++---
> 2 files changed, 70 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/host.S
> b/arch/arm64/kvm/hyp/nvhe/host.S
> index fe2740b224cf..2b56f0bdf874 100644
> --- a/arch/arm64/kvm/hyp/nvhe/host.S
> +++ b/arch/arm64/kvm/hyp/nvhe/host.S
> @@ -180,3 +180,41 @@ SYM_CODE_START(__kvm_hyp_host_vector)
> invalid_host_el1_vect // FIQ 32-bit EL1
> invalid_host_el1_vect // Error 32-bit EL1
> SYM_CODE_END(__kvm_hyp_host_vector)
> +
> +/*
> + * Forward SMC with arguments in struct kvm_cpu_context, and
> + * store the result into the same struct. Assumes SMCCC 1.2 or older.
> + *
> + * x0: struct kvm_cpu_context*
> + */
> +SYM_CODE_START(__kvm_hyp_host_forward_smc)
> + /*
> + * Use x18 to keep the pointer to the host context because
> + * x18 is callee-saved in SMCCC but not in AAPCS64.
> + */
> + mov x18, x0
> +
> + ldp x0, x1, [x18, #CPU_XREG_OFFSET(0)]
> + ldp x2, x3, [x18, #CPU_XREG_OFFSET(2)]
> + ldp x4, x5, [x18, #CPU_XREG_OFFSET(4)]
> + ldp x6, x7, [x18, #CPU_XREG_OFFSET(6)]
> + ldp x8, x9, [x18, #CPU_XREG_OFFSET(8)]
> + ldp x10, x11, [x18, #CPU_XREG_OFFSET(10)]
> + ldp x12, x13, [x18, #CPU_XREG_OFFSET(12)]
> + ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)]
> + ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)]
> +
> + smc #0
> +
> + stp x0, x1, [x18, #CPU_XREG_OFFSET(0)]
> + stp x2, x3, [x18, #CPU_XREG_OFFSET(2)]
> + stp x4, x5, [x18, #CPU_XREG_OFFSET(4)]
> + stp x6, x7, [x18, #CPU_XREG_OFFSET(6)]
> + stp x8, x9, [x18, #CPU_XREG_OFFSET(8)]
> + stp x10, x11, [x18, #CPU_XREG_OFFSET(10)]
> + stp x12, x13, [x18, #CPU_XREG_OFFSET(12)]
> + stp x14, x15, [x18, #CPU_XREG_OFFSET(14)]
> + stp x16, x17, [x18, #CPU_XREG_OFFSET(16)]
> +
> + ret
> +SYM_CODE_END(__kvm_hyp_host_forward_smc)
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index a4f1cac714d7..f25680ede080 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -18,6 +18,8 @@
>
> DEFINE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
>
> +void __kvm_hyp_host_forward_smc(struct kvm_cpu_context *host_ctxt);
> +
> static void handle___kvm_vcpu_run(struct kvm_cpu_context *host_ctxt)
> {
> DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1);
> @@ -152,12 +154,39 @@ static void handle_host_hcall(struct
> kvm_cpu_context *host_ctxt)
> cpu_reg(host_ctxt, 0) = SMCCC_RET_NOT_SUPPORTED;
> }
>
> +static void default_host_smc_handler(struct kvm_cpu_context
> *host_ctxt)
> +{
> + __kvm_hyp_host_forward_smc(host_ctxt);
> +}
> +
> +static void skip_host_instruction(void)
> +{
> + write_sysreg_el2(read_sysreg_el2(SYS_ELR) + 4, SYS_ELR);
> +}

Just for the sake of keeping things together, it'd be good to
move this helper to include/hyp/adjust_pc.h. Nothing urgent though.

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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