From: Stefano Stabellini <sstabellini@kernel.org>
To: Julien Grall <julien.grall@arm.com>
Cc: jgross@suse.com, xen-devel@lists.xenproject.org,
Stefano Stabellini <sstabellini@kernel.org>,
Volodymyr_Babchuk@epam.com,
Stefano Stabellini <stefano.stabellini@xilinx.com>
Subject: Re: [Xen-devel] [PATCH v2 1/3] xen/arm: fix buf size in make_cpus_node
Date: Tue, 8 Oct 2019 14:18:33 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.21.1910081413160.13684@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <06903f95-0135-c392-3e44-9a9928a3a6de@arm.com>
On Tue, 8 Oct 2019, Julien Grall wrote:
> On 10/8/19 2:14 AM, Stefano Stabellini wrote:
> > The size of buf is calculated wrongly: the number is 64bit, not 32bit.
>
> While the variable mpdir_aff is 64-bit, we only write the first 32-bit in the
> property reg (#address-cells == 1 and fdt_property_cell()). So what needs to
> be modified is the format here.
>
> Also, looking the CPU bindings (see
> linux/Documentation/devicetree/bindings/arm/cpus.yaml), technically only the
> bits [23:0] of the mpidr should be used. The rest is zeroed.
>
> This is ok because vcpuid_to_vaffinity() is always returning a value following
> the requirements above. However, for correctness, this may want to be fixed.
It looks like it would be best to change mpdir_aff to uint32_t and
change vcpuid_to_vaffinity to return a uint32_t.
Then of course the buf allocation would be buf[13].
Is that what you have in mind?
> > Also the number is printed as a hexadecimal number, so we need 8 bytes
> > for 32bit, not 10 bytes.
> >
> > As a result, it should be sizeof("cpu@") + 16 bytes for a 64-bit number
> > + 1 byte for \0. Total = 21.
> >
> > Fixes: fafd682c3e (xen/arm: Create a fake cpus node in dom0 device tree)
>
> I am afraid this is not fixing this patch:
>
> snprintf(buf, sizeof(buf), "cpu@%u", cpu);
>
> So the 10 bytes were actually correct back then.
>
> The problem was introduced by commit c81a791d34 "xen/arm: Set 'reg' of cpu
> node for dom0 to match MPIDR's affinity".
Yes, I'll change it
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
> > ---
> > Changes in v2:
> > - patch added
> > ---
> > xen/arch/arm/domain_build.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> > index 921b054520..60923a7051 100644
> > --- a/xen/arch/arm/domain_build.c
> > +++ b/xen/arch/arm/domain_build.c
> > @@ -788,8 +788,8 @@ static int __init make_cpus_node(const struct domain *d,
> > void *fdt)
> > unsigned int cpu;
> > const void *compatible = NULL;
> > u32 len;
> > - /* Placeholder for cpu@ + a 32-bit number + \0 */
> > - char buf[15];
> > + /* Placeholder for cpu@ + a 64-bit number + \0 */
> > + char buf[21];
> > u32 clock_frequency;
> > bool clock_valid;
> > uint64_t mpidr_aff;
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next prev parent reply other threads:[~2019-10-08 21:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 1:14 [Xen-devel] [PATCH for-4.13 v2 0/3] fixes for make_[memory/cpu]_node Stefano Stabellini
2019-10-08 1:14 ` [Xen-devel] [PATCH v2 1/3] xen/arm: fix buf size in make_cpus_node Stefano Stabellini
2019-10-08 11:15 ` Julien Grall
2019-10-08 21:18 ` Stefano Stabellini [this message]
2019-10-08 21:47 ` Julien Grall
2019-10-08 1:15 ` [Xen-devel] [PATCH v2 2/3] xen/arm: make_memory_node return error on nr_banks == 0 Stefano Stabellini
2019-10-08 12:53 ` Julien Grall
2019-10-08 1:15 ` [Xen-devel] [PATCH v2 3/3] xen/arm: fix duplicate memory node in DT Stefano Stabellini
2019-10-08 12:54 ` Julien Grall
2019-10-08 4:21 ` [Xen-devel] [PATCH for-4.13 v2 0/3] fixes for make_[memory/cpu]_node Jürgen Groß
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