Re: [PATCH v10 06/26] virt: gunyah: msgq: Add hypercalls to send and receive messages

[Elliot Berman]

On 2/23/2023 4:15 PM, Alex Elder wrote:
> On 2/14/23 3:23 PM, Elliot Berman wrote:
> > Add hypercalls to send and receive messages on a Gunyah message queue.
> >
> > Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
> > ---
> >   arch/arm64/gunyah/gunyah_hypercall.c | 32 ++++++++++++++++++++++++++++
> >   include/linux/gunyah.h               |  7 ++++++
> >   2 files changed, 39 insertions(+)
> >
> > diff --git a/arch/arm64/gunyah/gunyah_hypercall.c 
> > b/arch/arm64/gunyah/gunyah_hypercall.c
> > index f30d06ee80cf..2ca9ab098ff6 100644
> > --- a/arch/arm64/gunyah/gunyah_hypercall.c
> > +++ b/arch/arm64/gunyah/gunyah_hypercall.c
> > @@ -38,6 +38,8 @@ EXPORT_SYMBOL_GPL(arch_is_gunyah_guest);
> >                              fn)
> >   #define GH_HYPERCALL_HYP_IDENTIFY        GH_HYPERCALL(0x8000)
> > +#define GH_HYPERCALL_MSGQ_SEND            GH_HYPERCALL(0x801B)
> > +#define GH_HYPERCALL_MSGQ_RECV            GH_HYPERCALL(0x801C)
> >   /**
> >    * gh_hypercall_hyp_identify() - Returns build information and 
> > feature flags
> > @@ -57,5 +59,35 @@ void gh_hypercall_hyp_identify(struct 
> > gh_hypercall_hyp_identify_resp *hyp_identi
> >   }
> >   EXPORT_SYMBOL_GPL(gh_hypercall_hyp_identify);
> > +enum gh_error gh_hypercall_msgq_send(u64 capid, size_t size, 
> > uintptr_t buff, int tx_flags,
> > +                    bool *ready)
> > +{
> > +    struct arm_smccc_res res;
> > +
> > +    arm_smccc_1_1_hvc(GH_HYPERCALL_MSGQ_SEND, capid, size, buff, 
> > tx_flags, 0, &res);
> > +
> > +    if (res.a0 == GH_ERROR_OK)
> > +        *ready = res.a1;
> > +
> > +    return res.a0;
> > +}
> > +EXPORT_SYMBOL_GPL(gh_hypercall_msgq_send);
> > +
> > +enum gh_error gh_hypercall_msgq_recv(u64 capid, uintptr_t buff, 
> > size_t size, size_t *recv_size,
> > +                    bool *ready)
> > +{
> > +    struct arm_smccc_res res;
> > +
> > +    arm_smccc_1_1_hvc(GH_HYPERCALL_MSGQ_RECV, capid, buff, size, 0, 
> > &res);
> > +
> > +    if (res.a0 == GH_ERROR_OK) {
> > +        *recv_size = res.a1;
>
> Is there any chance the 64-bit size is incompatible
> with size_t?  (Too big?)

This is safe because size of messages <= 240.

> > +        *ready = res.a2;
>
>          *ready = !!res.a2;
>
> > +    }
> > +
> > +    return res.a0;
> > +}
> > +EXPORT_SYMBOL_GPL(gh_hypercall_msgq_recv);
> > +
> >   MODULE_LICENSE("GPL");
> >   MODULE_DESCRIPTION("Gunyah Hypervisor Hypercalls");
> > diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
> > index 3fef2854c5e1..cb6df4eec5c2 100644
> > --- a/include/linux/gunyah.h
> > +++ b/include/linux/gunyah.h
> > @@ -112,4 +112,11 @@ struct gh_hypercall_hyp_identify_resp {
> >   void gh_hypercall_hyp_identify(struct gh_hypercall_hyp_identify_resp 
> > *hyp_identity);
> > +#define GH_HYPERCALL_MSGQ_TX_FLAGS_PUSH        BIT(0)
> > +
> > +enum gh_error gh_hypercall_msgq_send(u64 capid, size_t size, 
> > uintptr_t buff, int tx_flags,
> > +                    bool *ready);
>
> Why uintptr_t?  Why not just pass a host pointer (void *)
> and do whatever conversion is necessary inside the function?
>
>                      -Alex
>
> > +enum gh_error gh_hypercall_msgq_recv(u64 capid, uintptr_t buff, 
> > size_t size, size_t *recv_size,
> > +                    bool *ready);
> > +
> >   #endif