On Tue, Jul 28, 2020 at 01:07:14AM +0000, Jianyong Wu wrote:
>
>
> > -----Original Message-----
> > From: Will Deacon <w...@kernel.org>
> > Sent: Monday, July 27, 2020 7:38 PM
> > To: Jianyong Wu <jianyong...@arm.com>
> > Cc: netdev@vger.kernel.org; yangbo...@nxp.com; john.stu...@linaro.org;
> > t...@linutronix.de; pbonz...@redhat.com; sean.j.christopher...@intel.com;
> > m...@kernel.org; richardcoch...@gmail.com; Mark Rutland
> > <mark.rutl...@arm.com>; Suzuki Poulose <suzuki.poul...@arm.com>;
> > Steven Price <steven.pr...@arm.com>; linux-ker...@vger.kernel.org; linux-
> > arm-ker...@lists.infradead.org; kvm...@lists.cs.columbia.edu;
> > k...@vger.kernel.org; Steve Capper <steve.cap...@arm.com>; Kaly Xin
> > <kaly....@arm.com>; Justin He <justin...@arm.com>; Wei Chen
> > <wei.c...@arm.com>; nd <n...@arm.com>
> > Subject: Re: [PATCH v13 2/9] arm/arm64: KVM: Advertise KVM UID to guests
> > via SMCCC
> >
> > On Mon, Jul 27, 2020 at 03:45:37AM +0000, Jianyong Wu wrote:
> > > > From: Will Deacon <w...@kernel.org>
> > > >
> > > > We can advertise ourselves to guests as KVM and provide a basic
> > > > features bitmap for discoverability of future hypervisor services.
> > > >
> > > > Cc: Marc Zyngier <m...@kernel.org>
> > > > Signed-off-by: Will Deacon <w...@kernel.org>
> > > > Signed-off-by: Jianyong Wu <jianyong...@arm.com>
> > > > ---
> > > > arch/arm64/kvm/hypercalls.c | 29 +++++++++++++++++++----------
> > > > 1 file changed, 19 insertions(+), 10 deletions(-)
> > > >
> > > > diff --git a/arch/arm64/kvm/hypercalls.c
> > > > b/arch/arm64/kvm/hypercalls.c index 550dfa3e53cd..db6dce3d0e23
> > > > 100644
> > > > --- a/arch/arm64/kvm/hypercalls.c
> > > > +++ b/arch/arm64/kvm/hypercalls.c
> > > > @@ -12,13 +12,13 @@
> > > > int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) {
> > > > u32 func_id = smccc_get_function(vcpu);
> > > > - long val = SMCCC_RET_NOT_SUPPORTED;
> > > > + u32 val[4] = {SMCCC_RET_NOT_SUPPORTED};
> > >
> > > There is a risk as this u32 value will return here and a u64 value
> > > will be obtained in guest. For example, The val[0] is initialized as
> > > -1 of 0xffffffff and the guest get 0xffffffff then it will be compared
> > > with -1 of 0xffffffffffffffff Also this problem exists for the
> > > transfer of address in u64 type. So the following assignment to "val"
> > > should be split into two
> > > u32 value and assign to val[0] and val[1] respectively.
> > > WDYT?
> >
> > Yes, I think you're right that this is a bug, but isn't the solution just
> > to make
> > that an array of 'long'?
> >
> > long val [4];
> >
> > That will sign-extend the negative error codes as required, while leaving
> > the
> > explicitly unsigned UID constants alone.
>
> Ok, that's much better. I will fix it at next version.
>
> By the way, I wonder when will you update this patch set. I see someone like
> me
> adopt this patch set as code base and need rebase it every time, so expect
> your update.
I'm not working on it, so please feel free to include it along with the
patches that add an upstream user.
Will
