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Iglesias" To: Julien Grall Cc: xen-devel@lists.xenproject.org, sstabellini@kernel.org, bertrand.marquis@arm.com, michal.orzel@amd.com, Volodymyr_Babchuk@epam.com, andrew.cooper3@citrix.com, edgar.iglesias@amd.com Subject: Re: [PATCH v2 2/3] xen/arm: dom0less: Add trap-unmapped-accesses Message-ID: References: <20250529155024.1284227-1-edgar.iglesias@gmail.com> <20250529155024.1284227-3-edgar.iglesias@gmail.com> <8c93db26-fd37-4e37-9822-54986e5ee3cc@xen.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8c93db26-fd37-4e37-9822-54986e5ee3cc@xen.org> User-Agent: Mutt/2.2.14+84 (2efcabc4) (2025-03-23) On Thu, May 29, 2025 at 05:03:12PM +0100, Julien Grall wrote: > Hi Edgar, > > On 29/05/2025 16:50, Edgar E. Iglesias wrote: > > From: "Edgar E. Iglesias" > > > > Add the trap-unmapped-accesses per-domain fdt property. > > > > Signed-off-by: Edgar E. Iglesias > > --- > > docs/misc/arm/device-tree/booting.txt | 9 +++++++++ > > xen/arch/arm/dom0less-build.c | 9 ++++++++- > > 2 files changed, 17 insertions(+), 1 deletion(-) > > > > diff --git a/docs/misc/arm/device-tree/booting.txt b/docs/misc/arm/device-tree/booting.txt > > index 59fa96a82e..8a5c40ddf3 100644 > > --- a/docs/misc/arm/device-tree/booting.txt > > +++ b/docs/misc/arm/device-tree/booting.txt > > @@ -225,6 +225,15 @@ with the following properties: > > option is provided with a non zero value, but the platform doesn't support > > SVE. > > +- trap-unmapped-accesses > > + > > + Optional. An integer that configures handling of accesses to unmapped > > + address ranges. > > + If set to 0, guest accesses will read 0xFFFFFFFF and writes will be ignored. > > Looking at the code, if I am not mistaken, it will only return this value > for 32-bit. For 64-bit there will be a few Fs more and for less there will > be less. So I think this needs to be reworded. > > The rest looks good to me. Thanks, in v3 I'll change it to: If set to 0, guest accesses will read all bits as ones, e.g 0xFFFFFFFF for a 32bit access and writes will be ignored. Cheers, Edgar > > > + > > + This option is only implemented for ARM where the default is 1. > > + > > - xen,enhanced > > A string property. Possible property values are: > > diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c > > index a4e0a33632..69324aa597 100644 > > --- a/xen/arch/arm/dom0less-build.c > > +++ b/xen/arch/arm/dom0less-build.c > > @@ -344,8 +344,15 @@ void __init arch_create_domUs(struct dt_device_node *node, > > #endif > > } > > - /* Trap accesses to unmapped areas. */ > > + /* Trap unmapped accesses by default. */ > > d_cfg->flags |= XEN_DOMCTL_CDF_trap_unmapped_accesses; > > + if ( dt_property_read_u32(node, "trap-unmapped-accesses", &val) ) > > + { > > + if ( val > 1 ) > > + panic("trap-unmapped-accesses: supported values are 0 or 1"); > > + if ( !val ) > > + d_cfg->flags &= ~XEN_DOMCTL_CDF_trap_unmapped_accesses; > > + } > > } > > int __init init_intc_phandle(struct kernel_info *kinfo, const char *name, > > Cheers, > > -- > Julien Grall >