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Message-ID: <20250515164606.GB12396@willie-the-truck>
Date: Thu, 15 May 2025 17:46:06 +0100
From: Will Deacon <will@...nel.org>
To: perlarsen@...gle.com
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
Joey Gouly <joey.gouly@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Zenghui Yu <yuzenghui@...wei.com>,
Catalin Marinas <catalin.marinas@....com>,
Sudeep Holla <sudeep.holla@....com>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
linux-kernel@...r.kernel.org, sebastianene@...gle.com,
lpieralisi@...nel.org, arve@...roid.com, qwandor@...gle.com,
kernel-team@...roid.com, armellel@...gle.com, perl@...unant.com,
jean-philippe@...aro.org, ahomescu@...gle.com, tabba@...gle.com,
qperret@...gle.com, james.morse@....com
Subject: Re: [PATCH v3 3/3] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ2 in
host handler
On Tue, May 13, 2025 at 06:28:32AM +0000, Per Larsen via B4 Relay wrote:
> From: Per Larsen <perlarsen@...gle.com>
>
> FF-A 1.2 adds the DIRECT_REQ2 messaging interface which is similar to
> the existing FFA_MSG_SEND_DIRECT_{REQ,RESP} functions except that it
> uses the SMC calling convention v1.2 which allows calls to use x4-x17 as
> argument and return registers. Add support for FFA_MSG_SEND_DIRECT_REQ2
> in the host ffa handler.
>
> Signed-off-by: Per Larsen <perlarsen@...gle.com>
> Signed-off-by: Per Larsen <perl@...unant.com>
> ---
> arch/arm64/kvm/hyp/nvhe/ffa.c | 111 +++++++++++++++++++++++++++++++++++++++++-
> include/linux/arm_ffa.h | 2 +
> 2 files changed, 111 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 403fde6ca4d6ec49566ef60709cedbaef9f04592..437289aa5d902b0d2a4a8760403f0190f2320813 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -79,6 +79,14 @@ static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
> };
> }
>
> +static void ffa_to_smccc_1_2_error(struct arm_smccc_1_2_regs *regs, u64 ffa_errno)
> +{
> + *regs = (struct arm_smccc_1_2_regs) {
> + .a0 = FFA_ERROR,
> + .a2 = ffa_errno,
> + };
> +}
> +
> static void ffa_to_smccc_res_prop(struct arm_smccc_res *res, int ret, u64 prop)
> {
> if (ret == FFA_RET_SUCCESS) {
> @@ -89,11 +97,25 @@ static void ffa_to_smccc_res_prop(struct arm_smccc_res *res, int ret, u64 prop)
> }
> }
>
> +static void ffa_to_smccc_1_2_regs_prop(struct arm_smccc_1_2_regs *regs, int ret, u64 prop)
> +{
> + if (ret == FFA_RET_SUCCESS)
> + *regs = (struct arm_smccc_1_2_regs) { .a0 = FFA_SUCCESS,
> + .a2 = prop };
> + else
> + ffa_to_smccc_1_2_error(regs, ret);
> +}
> +
> static void ffa_to_smccc_res(struct arm_smccc_res *res, int ret)
> {
> ffa_to_smccc_res_prop(res, ret, 0);
> }
>
> +static void ffa_to_smccc_1_2_regs(struct arm_smccc_1_2_regs *regs, int ret)
> +{
> + ffa_to_smccc_1_2_regs_prop(regs, ret, 0);
> +}
> +
> static void ffa_set_retval(struct kvm_cpu_context *ctxt,
> struct arm_smccc_res *res)
> {
> @@ -131,6 +153,29 @@ static void ffa_set_retval(struct kvm_cpu_context *ctxt,
> }
> }
>
> +static void ffa_set_retval_smccc_1_2(struct kvm_cpu_context *ctxt,
> + struct arm_smccc_1_2_regs *regs)
> +{
> + cpu_reg(ctxt, 0) = regs->a0;
> + cpu_reg(ctxt, 1) = regs->a1;
> + cpu_reg(ctxt, 2) = regs->a2;
> + cpu_reg(ctxt, 3) = regs->a3;
> + cpu_reg(ctxt, 4) = regs->a4;
> + cpu_reg(ctxt, 5) = regs->a5;
> + cpu_reg(ctxt, 6) = regs->a6;
> + cpu_reg(ctxt, 7) = regs->a7;
> + cpu_reg(ctxt, 8) = regs->a8;
> + cpu_reg(ctxt, 9) = regs->a9;
> + cpu_reg(ctxt, 10) = regs->a10;
> + cpu_reg(ctxt, 11) = regs->a11;
> + cpu_reg(ctxt, 12) = regs->a12;
> + cpu_reg(ctxt, 13) = regs->a13;
> + cpu_reg(ctxt, 14) = regs->a14;
> + cpu_reg(ctxt, 15) = regs->a15;
> + cpu_reg(ctxt, 16) = regs->a16;
> + cpu_reg(ctxt, 17) = regs->a17;
> +}
> +
> /* Call SMC64 using SMCCC 1.2 if hyp negotiated FF-A 1.2 falling back to 1.1 */
> static void arm_smccc_1_x_smc(u64 func_id, u64 a1, u64 a2, u64 a3,
> u64 a4, u64 a5, u64 a6, u64 a7,
> @@ -686,7 +731,6 @@ static bool ffa_call_supported(u64 func_id)
> case FFA_NOTIFICATION_GET:
> case FFA_NOTIFICATION_INFO_GET:
> /* Unimplemented interfaces added in FF-A 1.2 */
> - case FFA_MSG_SEND_DIRECT_REQ2:
> case FFA_MSG_SEND_DIRECT_RESP2:
> case FFA_CONSOLE_LOG:
> case FFA_PARTITION_INFO_GET_REGS:
> @@ -697,6 +741,21 @@ static bool ffa_call_supported(u64 func_id)
> return true;
> }
>
> +/*
> + * Must a given FFA function use the SMC calling convention v1.2?
> + */
> +static bool ffa_call_needs_smccc_1_2(u64 func_id)
> +{
> + switch (func_id) {
> + case FFA_MSG_SEND_DIRECT_REQ2:
> + case FFA_MSG_SEND_DIRECT_RESP2:
> + case FFA_PARTITION_INFO_GET_REGS:
> + return true;
> + }
> +
> + return false;
> +}
> +
> static bool do_ffa_features(struct arm_smccc_res *res,
> struct kvm_cpu_context *ctxt)
> {
> @@ -855,9 +914,47 @@ static void do_ffa_part_get(struct arm_smccc_res *res,
> hyp_spin_unlock(&host_buffers.lock);
> }
>
> +static void do_ffa_direct_msg2(struct arm_smccc_1_2_regs *regs,
> + struct kvm_cpu_context *ctxt,
> + u64 vm_handle)
> +{
> + DECLARE_REG(u32, func_id, ctxt, 0);
> + DECLARE_REG(u32, endp, ctxt, 1);
> + DECLARE_REG(u64, uuid_lo, ctxt, 2);
> + DECLARE_REG(u64, uuid_hi, ctxt, 3);
> + DECLARE_REG(u64, x4, ctxt, 4);
> + DECLARE_REG(u64, x5, ctxt, 5);
> + DECLARE_REG(u64, x6, ctxt, 6);
> + DECLARE_REG(u64, x7, ctxt, 7);
> + DECLARE_REG(u64, x8, ctxt, 8);
> + DECLARE_REG(u64, x9, ctxt, 9);
> + DECLARE_REG(u64, x10, ctxt, 10);
> + DECLARE_REG(u64, x11, ctxt, 11);
> + DECLARE_REG(u64, x12, ctxt, 12);
> + DECLARE_REG(u64, x13, ctxt, 13);
> + DECLARE_REG(u64, x14, ctxt, 14);
> + DECLARE_REG(u64, x15, ctxt, 15);
> + DECLARE_REG(u64, x16, ctxt, 16);
> + DECLARE_REG(u64, x17, ctxt, 17);
> +
> + if (FIELD_GET(FFA_SRC_ENDPOINT_MASK, endp) != vm_handle) {
> + ffa_to_smccc_1_2_regs(regs, FFA_RET_INVALID_PARAMETERS);
Just call ffa_to_smccc_1_2_error() here?
> + return;
> + }
> +
> + struct arm_smccc_1_2_regs args = {
> + func_id, endp, uuid_lo, uuid_hi,
> + x4, x5, x6, x7, x8, x9, x10,
> + x11, x12, x13, x14, x15, x16, x17
> + };
> +
> + arm_smccc_1_2_smc(&args, regs);
> +}
> +
> bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
> {
> struct arm_smccc_res res;
> + struct arm_smccc_1_2_regs regs;
>
> /*
> * There's no way we can tell what a non-standard SMC call might
> @@ -913,14 +1010,24 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
> case FFA_PARTITION_INFO_GET:
> do_ffa_part_get(&res, host_ctxt);
> goto out_handled;
> + case FFA_MSG_SEND_DIRECT_REQ2:
> + if (ffa_get_hypervisor_version() >= FFA_VERSION_1_2) {
> + do_ffa_direct_msg2(®s, host_ctxt, HOST_FFA_ID);
> + goto out_handled;
> + }
> + goto out_not_supported;
> }
>
> if (ffa_call_supported(func_id))
> return false; /* Pass through */
>
> +out_not_supported:
> ffa_to_smccc_error(&res, FFA_RET_NOT_SUPPORTED);
> out_handled:
> - ffa_set_retval(host_ctxt, &res);
> + if (ffa_call_needs_smccc_1_2(func_id))
Could we push this check lower down? The host_ctxt contains the func_id,
so we could (a) stop taking it as an extra parameter to
kvm_host_psci_handler() and kvm_host_ffa_handler(), (b) add a helper to
extract it and (c) ffa_set_retval() could handle the registers
appropriately to the call.
Will
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