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Message-ID: <86r09r70hj.wl-maz@kernel.org>
Date: Tue, 10 Sep 2024 20:49:28 +0100
From: Marc Zyngier <maz@...nel.org>
To: Oliver Upton <oliver.upton@...ux.dev>
Cc: Wei-Lin Chang <r09922117@...e.ntu.edu.tw>,
Snehal Koukuntla <snehalreddy@...gle.com>,
James Morse <james.morse@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Zenghui Yu <yuzenghui@...wei.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Sudeep Holla <sudeep.holla@....com>,
Sebastian Ene <sebastianene@...gle.com>,
Vincent Donnefort <vdonnefort@...gle.com>,
Jean-Philippe Brucker <jean-philippe@...aro.org>,
linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.linux.dev,
linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Subject: Re: [PATCH v3] KVM: arm64: Add memory length checks and remove inline in do_ffa_mem_xfer
On Tue, 10 Sep 2024 19:18:41 +0100,
Oliver Upton <oliver.upton@...ux.dev> wrote:
>
> On Wed, Sep 11, 2024 at 12:32:29AM +0800, Wei-Lin Chang wrote:
> > Hi everyone,
> >
> > On Mon, Sep 09, 2024 at 06:01:54PM GMT, Snehal Koukuntla wrote:
> > > When we share memory through FF-A and the description of the buffers
> > > exceeds the size of the mapped buffer, the fragmentation API is used.
> > > The fragmentation API allows specifying chunks of descriptors in subsequent
> > > FF-A fragment calls and no upper limit has been established for this.
> > > The entire memory region transferred is identified by a handle which can be
> > > used to reclaim the transferred memory.
> > > To be able to reclaim the memory, the description of the buffers has to fit
> > > in the ffa_desc_buf.
> > > Add a bounds check on the FF-A sharing path to prevent the memory reclaim
> > > from failing.
> > >
> > > Also do_ffa_mem_xfer() does not need __always_inline
> > >
> > > Fixes: 634d90cf0ac65 ("KVM: arm64: Handle FFA_MEM_LEND calls from the host")
> > > Cc: stable@...r.kernel.org
> > > Reviewed-by: Sebastian Ene <sebastianene@...gle.com>
> > > Signed-off-by: Snehal Koukuntla <snehalreddy@...gle.com>
> > > ---
> > > arch/arm64/kvm/hyp/nvhe/ffa.c | 7 ++++++-
> > > 1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> > > index e715c157c2c4..637425f63fd1 100644
> > > --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> > > +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> > > @@ -426,7 +426,7 @@ static void do_ffa_mem_frag_tx(struct arm_smccc_res *res,
> > > return;
> > > }
> > >
> > > -static __always_inline void do_ffa_mem_xfer(const u64 func_id,
> > > +static void do_ffa_mem_xfer(const u64 func_id,
> >
> > I am seeing a compilation error because of this.
>
> Thanks for reporting this. Looks like the __always_inline was slightly
> more load bearing...
>
> Marc, can you put something like this on top?
>
>
> From c2712eaa94989ae6457baad3ec459cf363ec5119 Mon Sep 17 00:00:00 2001
> From: Oliver Upton <oliver.upton@...ux.dev>
> Date: Tue, 10 Sep 2024 16:45:30 +0000
> Subject: [PATCH] KVM: arm64: Drop BUILD_BUG_ON() from do_ffa_mem_xfer()
>
> __always_inline was recently discarded from do_ffa_mem_xfer() since it
> appeared to be unnecessary. Of course, this was ~immediately proven
> wrong, as the compile-time check against @func_id depends on inlining
> for the value to be known.
>
> Just downgrade to a WARN_ON() instead of putting the old mess back in
> place. Fix the wrapping/indentation of the function parameters while at
> it.
>
> Fixes: 39dacbeeee70 ("KVM: arm64: Add memory length checks and remove inline in do_ffa_mem_xfer")
> Reported-by: Wei-Lin Chang <r09922117@...e.ntu.edu.tw>
> Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
> ---
> arch/arm64/kvm/hyp/nvhe/ffa.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 637425f63fd1..316d269341f3 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -426,9 +426,8 @@ static void do_ffa_mem_frag_tx(struct arm_smccc_res *res,
> return;
> }
>
> -static void do_ffa_mem_xfer(const u64 func_id,
> - struct arm_smccc_res *res,
> - struct kvm_cpu_context *ctxt)
> +static void do_ffa_mem_xfer(const u64 func_id, struct arm_smccc_res *res,
> + struct kvm_cpu_context *ctxt)
> {
> DECLARE_REG(u32, len, ctxt, 1);
> DECLARE_REG(u32, fraglen, ctxt, 2);
> @@ -440,8 +439,10 @@ static void do_ffa_mem_xfer(const u64 func_id,
> u32 offset, nr_ranges;
> int ret = 0;
>
> - BUILD_BUG_ON(func_id != FFA_FN64_MEM_SHARE &&
> - func_id != FFA_FN64_MEM_LEND);
> + if (WARN_ON(func_id != FFA_FN64_MEM_SHARE && func_id != FFA_FN64_MEM_LEND)) {
> + ret = SMCCC_RET_NOT_SUPPORTED;
> + goto out;
> + }
I'm not overly on the WARN_ON(), as it has pretty fatal effects on
pKVM (it simply panics). What do you think of this instead, which
compiles with my prehistoric version of clang (14.0.6):
diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 637425f63fd1b..e433dfab882aa 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -426,9 +426,9 @@ static void do_ffa_mem_frag_tx(struct arm_smccc_res *res,
return;
}
-static void do_ffa_mem_xfer(const u64 func_id,
- struct arm_smccc_res *res,
- struct kvm_cpu_context *ctxt)
+static void __do_ffa_mem_xfer(const u64 func_id,
+ struct arm_smccc_res *res,
+ struct kvm_cpu_context *ctxt)
{
DECLARE_REG(u32, len, ctxt, 1);
DECLARE_REG(u32, fraglen, ctxt, 2);
@@ -440,9 +440,6 @@ static void do_ffa_mem_xfer(const u64 func_id,
u32 offset, nr_ranges;
int ret = 0;
- BUILD_BUG_ON(func_id != FFA_FN64_MEM_SHARE &&
- func_id != FFA_FN64_MEM_LEND);
-
if (addr_mbz || npages_mbz || fraglen > len ||
fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
ret = FFA_RET_INVALID_PARAMETERS;
@@ -517,6 +514,13 @@ static void do_ffa_mem_xfer(const u64 func_id,
goto out_unlock;
}
+#define do_ffa_mem_xfer(fid, res, ctxt) \
+ do { \
+ BUILD_BUG_ON((fid) != FFA_FN64_MEM_SHARE && \
+ (fid) != FFA_FN64_MEM_LEND); \
+ __do_ffa_mem_xfer((fid), (res), (ctxt)); \
+ } while (0);
+
static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
struct kvm_cpu_context *ctxt)
{
It preserves the build-time assertion, which was the intention of the
original author.
I can easily squash that in the original commit, avoiding the headache
of backporting both patch to stable.
M.
--
Without deviation from the norm, progress is not possible.
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