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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [XEN PATCH v7 10/20] xen/arm: ffa: add direct request support
Hi,
On Wed, Mar 1, 2023 at 2:06 PM Bertrand Marquis
<Bertrand.Marquis@xxxxxxx> wrote:
>
> HI Jens,
>
> > On 1 Mar 2023, at 11:55, Jens Wiklander <jens.wiklander@xxxxxxxxxx> wrote:
> >
> > Hi Bertrand,
> >
> > On Mon, Feb 27, 2023 at 4:28 PM Bertrand Marquis
> > <Bertrand.Marquis@xxxxxxx> wrote:
> >>
> >> Hi Jens,
> >>
> >>> On 22 Feb 2023, at 16:33, Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> >>> wrote:
> >>>
> >>> Adds support for sending a FF-A direct request. Checks that the SP also
> >>> supports handling a 32-bit direct request. 64-bit direct requests are
> >>> not used by the mediator itself so there is not need to check for that.
> >>>
> >>> Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> >>> ---
> >>> xen/arch/arm/tee/ffa.c | 119 +++++++++++++++++++++++++++++++++++++++++
> >>> 1 file changed, 119 insertions(+)
> >>>
> >>> diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
> >>> index 463fd7730573..a5d8a12635b6 100644
> >>> --- a/xen/arch/arm/tee/ffa.c
> >>> +++ b/xen/arch/arm/tee/ffa.c
> >>> @@ -142,6 +142,7 @@
> >>>
> >>> struct ffa_ctx {
> >>> uint32_t guest_vers;
> >>> + bool interrupted;
> >>
> >> This is added and set here for one special error code but is never used.
> >> I would suggest to introduce this when there will be an action based on it.
> >
> > I'm sorry, I forgot about completing this. I'll add code to deal with
> > FFA_INTERRUPT. This will be tricky to test though since we don't use
> > FFA_INTERRUPT like this with OP-TEE. The Hypervisor is required by the
> > FF-A standard to support it so I better add something.
>
> You can do that in a different patch then and just remove this from this
> patch ?
OK, I'll do that.
>
> >
> >>
> >>> };
> >>>
> >>> /* Negotiated FF-A version to use with the SPMC */
> >>> @@ -167,6 +168,55 @@ static bool ffa_get_version(uint32_t *vers)
> >>> return true;
> >>> }
> >>>
> >>> +static int32_t get_ffa_ret_code(const struct arm_smccc_1_2_regs *resp)
> >>> +{
> >>> + switch ( resp->a0 )
> >>> + {
> >>> + case FFA_ERROR:
> >>> + if ( resp->a2 )
> >>> + return resp->a2;
> >>> + else
> >>> + return FFA_RET_NOT_SUPPORTED;
> >>> + case FFA_SUCCESS_32:
> >>> + case FFA_SUCCESS_64:
> >>> + return FFA_RET_OK;
> >>> + default:
> >>> + return FFA_RET_NOT_SUPPORTED;
> >>> + }
> >>> +}
> >>> +
> >>> +static int32_t ffa_simple_call(uint32_t fid, register_t a1, register_t
> >>> a2,
> >>> + register_t a3, register_t a4)
> >>> +{
> >>> + const struct arm_smccc_1_2_regs arg = {
> >>> + .a0 = fid,
> >>> + .a1 = a1,
> >>> + .a2 = a2,
> >>> + .a3 = a3,
> >>> + .a4 = a4,
> >>> + };
> >>> + struct arm_smccc_1_2_regs resp;
> >>> +
> >>> + arm_smccc_1_2_smc(&arg, &resp);
> >>> +
> >>> + return get_ffa_ret_code(&resp);
> >>> +}
> >>> +
> >>> +static int32_t ffa_features(uint32_t id)
> >>> +{
> >>> + return ffa_simple_call(FFA_FEATURES, id, 0, 0, 0);
> >>> +}
> >>> +
> >>> +static bool check_mandatory_feature(uint32_t id)
> >>> +{
> >>> + uint32_t ret = ffa_features(id);
> >>> +
> >>> + if (ret)
> >>> + printk(XENLOG_ERR "ffa: mandatory feature id %#x missing\n", id);
> >>
> >> It might be useful here to actually print the error code.
> >> Are we sure that all errors actually mean not supported ?
> >
> > Yes, that's what the standard says.
>
> The error code might still be useful in the print.
OK, I'll add it.
>
> >
> >>
> >>> +
> >>> + return !ret;
> >>> +}
> >>> +
> >>> static uint16_t get_vm_id(const struct domain *d)
> >>> {
> >>> /* +1 since 0 is reserved for the hypervisor in FF-A */
> >>> @@ -208,6 +258,66 @@ static void handle_version(struct cpu_user_regs
> >>> *regs)
> >>> set_regs(regs, vers, 0, 0, 0, 0, 0, 0, 0);
> >>> }
> >>>
> >>> +static void handle_msg_send_direct_req(struct cpu_user_regs *regs,
> >>> uint32_t fid)
> >>> +{
> >>> + struct arm_smccc_1_2_regs arg = { .a0 = fid, };
> >>> + struct arm_smccc_1_2_regs resp = { };
> >>> + struct domain *d = current->domain;
> >>> + struct ffa_ctx *ctx = d->arch.tee;
> >>> + uint32_t src_dst;
> >>> + uint64_t mask;
> >>> +
> >>> + if ( smccc_is_conv_64(fid) )
> >>> + mask = GENMASK_ULL(63, 0);
> >>> + else
> >>> + mask = GENMASK_ULL(31, 0);
> >>> +
> >>> + src_dst = get_user_reg(regs, 1);
> >>> + if ( (src_dst >> 16) != get_vm_id(d) )
> >>> + {
> >>> + resp.a0 = FFA_ERROR;
> >>> + resp.a2 = FFA_RET_INVALID_PARAMETERS;
> >>> + goto out;
> >>> + }
> >>> +
> >>> + arg.a1 = src_dst;
> >>> + arg.a2 = get_user_reg(regs, 2) & mask;
> >>> + arg.a3 = get_user_reg(regs, 3) & mask;
> >>> + arg.a4 = get_user_reg(regs, 4) & mask;
> >>> + arg.a5 = get_user_reg(regs, 5) & mask;
> >>> + arg.a6 = get_user_reg(regs, 6) & mask;
> >>> + arg.a7 = get_user_reg(regs, 7) & mask;
> >>> +
> >>> + while ( true )
> >>> + {
> >>> + arm_smccc_1_2_smc(&arg, &resp);
> >>> +
> >>> + switch ( resp.a0 )
> >>> + {
> >>> + case FFA_INTERRUPT:
> >>> + ctx->interrupted = true;
> >>> + goto out;
> >>> + case FFA_ERROR:
> >>> + case FFA_SUCCESS_32:
> >>> + case FFA_SUCCESS_64:
> >>> + case FFA_MSG_SEND_DIRECT_RESP_32:
> >>> + case FFA_MSG_SEND_DIRECT_RESP_64:
> >>> + goto out;
> >>> + default:
> >>> + /* Bad fid, report back. */
> >>> + memset(&arg, 0, sizeof(arg));
> >>> + arg.a0 = FFA_ERROR;
> >>> + arg.a1 = src_dst;
> >>> + arg.a2 = FFA_RET_NOT_SUPPORTED;
> >>> + continue;
> >>
> >> There is a potential infinite loop here and i do not understand
> >> why this needs to be done.
> >> Here if something is returning a value that you do not understand
> >> you send back an ERROR to it. I do not find in the spec where this
> >> is supposed to be done.
> >> Can you explain a bit here ?
> >
> > This should normally not happen, but the SP/SPMC is responding with a
> > request that we don't know what to do with. The standard doesn't say
> > how to handle that as far as I understand. However, returning back to
> > the VM at this point with an error may leave the SP/SPMC in a strange
> > state. So I think it's better to report back to the SP/SPMC that the
> > request isn't understood and hopefully it can at least return back
> > with an error in a sane state.
> >
> > I'll add something to the comment.
>
> Please also make sure that the code is not looping infinitely on this.
I'll remove the loop as agreed in the other mail.
>
> >
> >>
> >>> + }
> >>> + }
> >>> +
> >>> +out:
> >>> + set_regs(regs, resp.a0, resp.a1 & mask, resp.a2 & mask, resp.a3 &
> >>> mask,
> >>> + resp.a4 & mask, resp.a5 & mask, resp.a6 & mask, resp.a7 &
> >>> mask);
> >>> +}
> >>> +
> >>> static bool ffa_handle_call(struct cpu_user_regs *regs)
> >>> {
> >>> uint32_t fid = get_user_reg(regs, 0);
> >>> @@ -225,6 +335,12 @@ static bool ffa_handle_call(struct cpu_user_regs
> >>> *regs)
> >>> case FFA_ID_GET:
> >>> set_regs_success(regs, get_vm_id(d), 0);
> >>> return true;
> >>> + case FFA_MSG_SEND_DIRECT_REQ_32:
> >>> +#ifdef CONFIG_ARM_64
> >>> + case FFA_MSG_SEND_DIRECT_REQ_64:
> >>> +#endif
> >>> + handle_msg_send_direct_req(regs, fid);
> >>> + return true;
> >>>
> >>> default:
> >>> gprintk(XENLOG_ERR, "ffa: unhandled fid 0x%x\n", fid);
> >>> @@ -310,6 +426,9 @@ static bool ffa_probe(void)
> >>> printk(XENLOG_INFO "ARM FF-A Firmware version %u.%u\n",
> >>> major_vers, minor_vers);
> >>>
> >>> + if ( !check_mandatory_feature(FFA_MSG_SEND_DIRECT_REQ_32) )
> >>> + return false;
> >>
> >> One could not need this feature and here this will make everything
> >> unavailable instead.
> >> Why not just reporting back the unsupported error to clients using
> >> unsupported interfaces ?
> >
> > One could perhaps argue that this check should be moved to a later
> > patch in this series. Perhaps there's some future configuration that
> > might make sense without this feature, but for now, it doesn't make
> > sense to initialize without it.
>
> I am starting to wonder if we should not at boot scan for available features,
> save them
> somewhere and then accept/reject calls depending on the supported features.
>
> Maybe just add a TODO here so that we remember that this is something that
> could be
> checked/modified one day. That would also give an insight if someone has such
> a usecase
> one day.
I'll add a comment.
Cheers,
Jens
>
> Cheers
> Bertrand
>
> >
> > Thanks,
> > Jens
> >
> >>
> >> Cheers
> >> Bertrand
> >>
> >>> +
> >>> ffa_version = vers;
> >>>
> >>> return true;
> >>> --
> >>> 2.34.1
>
>
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