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Message-ID: <ZR1lGOUNyr77qtGp@bogus>
Date: Wed, 4 Oct 2023 14:22:24 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Marc Zyngier <maz@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Marc Bonnici <marc.bonnici@....com>,
Sudeep Holla <sudeep.holla@....com>,
Jens Wiklander <jens.wiklander@...aro.org>,
Coboy Chen <coboy.chen@...iatek.com>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Olivier Deprez <olivier.deprez@....com>,
Oliver Upton <oliver.upton@...ux.dev>,
Will Deacon <will@...nel.org>,
Quentin Perret <qperret@...gle.com>
Subject: Re: [PATCH v3 14/17] KVM: arm64: FFA: Remove access of endpoint
memory access descriptor array
On Wed, Oct 04, 2023 at 11:08:23AM +0100, Marc Zyngier wrote:
> On Fri, 29 Sep 2023 16:03:03 +0100,
> Sudeep Holla <sudeep.holla@....com> wrote:
> >
> > FF-A v1.1 removes the fixed location of endpoint memory access descriptor
> > array within the memory transaction descriptor structure. In preparation
> > to remove the ep_mem_access member from the ffa_mem_region structure,
> > provide the accessor to fetch the offset and use the same in FF-A proxy
> > implementation.
> >
> > The accessor take the boolean argument that indicates if the memory access
> > descriptor versions is v1(old format) or not. Currently it is set true as
> > FF-A proxy supports only v1.0
> >
> > Cc: Marc Zyngier <maz@...nel.org>
> > Cc: Oliver Upton <oliver.upton@...ux.dev>
> > Cc: Will Deacon <will@...nel.org>
> > Cc: Quentin Perret <qperret@...gle.com>
> > Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> > ---
> > arch/arm64/kvm/hyp/nvhe/ffa.c | 8 ++++++--
> > include/linux/arm_ffa.h | 6 ++++++
> > 2 files changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> > index 6e4dba9eadef..5f956f53e6bf 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> > @@ -423,6 +423,7 @@ static __always_inline void do_ffa_mem_xfer(const u64 func_id,
> > DECLARE_REG(u32, fraglen, ctxt, 2);
> > DECLARE_REG(u64, addr_mbz, ctxt, 3);
> > DECLARE_REG(u32, npages_mbz, ctxt, 4);
> > + struct ffa_mem_region_attributes *ep_mem_access;
> > struct ffa_composite_mem_region *reg;
> > struct ffa_mem_region *buf;
> > u32 offset, nr_ranges;
> > @@ -452,7 +453,8 @@ static __always_inline void do_ffa_mem_xfer(const u64 func_id,
> > buf = hyp_buffers.tx;
> > memcpy(buf, host_buffers.tx, fraglen);
> >
> > - offset = buf->ep_mem_access[0].composite_off;
> > + ep_mem_access = (void *)buf + ffa_mem_desc_offset(buf, 0, true);
> > + offset = ep_mem_access->composite_off;
> > if (!offset || buf->ep_count != 1 || buf->sender_id != HOST_FFA_ID) {
> > ret = FFA_RET_INVALID_PARAMETERS;
> > goto out_unlock;
> > @@ -504,6 +506,7 @@ static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
> > DECLARE_REG(u32, handle_lo, ctxt, 1);
> > DECLARE_REG(u32, handle_hi, ctxt, 2);
> > DECLARE_REG(u32, flags, ctxt, 3);
> > + struct ffa_mem_region_attributes *ep_mem_access;
> > struct ffa_composite_mem_region *reg;
> > u32 offset, len, fraglen, fragoff;
> > struct ffa_mem_region *buf;
> > @@ -528,7 +531,8 @@ static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
> > len = res->a1;
> > fraglen = res->a2;
> >
> > - offset = buf->ep_mem_access[0].composite_off;
> > + ep_mem_access = (void *)buf + ffa_mem_desc_offset(buf, 0, true);
> > + offset = ep_mem_access->composite_off;
> > /*
> > * We can trust the SPMD to get this right, but let's at least
> > * check that we end up with something that doesn't look _completely_
> > diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
> > index 748d0a83a4bc..7be240e37f36 100644
> > --- a/include/linux/arm_ffa.h
> > +++ b/include/linux/arm_ffa.h
> > @@ -357,6 +357,12 @@ struct ffa_mem_region {
> > #define CONSTITUENTS_OFFSET(x) \
> > (offsetof(struct ffa_composite_mem_region, constituents[x]))
> >
> > +static inline u32
> > +ffa_mem_desc_offset(struct ffa_mem_region *buf, int count, bool mem_desc_v1)
> > +{
> > + return COMPOSITE_OFFSET(0);
> > +}
>
> If the goal of this patch is to introduce some versioning, why not
> define this last parameter as an actual version number, PSCI style
> (with a minor and major, each on a 16bit field)?
>
Fair enough. I am being optimistic that the memory descriptor format doesn't
change with each FF-A version. And the v2 of the memory descriptor format is
quite flexible to provide backward compatibility for some time(I agree that
is controversial :))
> Even the name is pretty misleading, as both FFA versions are v1 (v1.0
> vs v1.1...).
>
I was referring to the memory descriptor format version. The intention was
to keep it separate from the FF-A version. But if using FF-A version makes
things simpler I can go for that.
--
Regards,
Sudeep
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