Messages in this thread | | | Subject | Re: [PATCH v2] xen: don't require virtio with grants for non-PV guests | From | Oleksandr <> | Date | Thu, 16 Jun 2022 10:31:42 +0300 |
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On 16.06.22 08:37, Juergen Gross wrote:
Hello Juergen
> Commit fa1f57421e0b ("xen/virtio: Enable restricted memory access using > Xen grant mappings") introduced a new requirement for using virtio > devices: the backend now needs to support the VIRTIO_F_ACCESS_PLATFORM > feature. > > This is an undue requirement for non-PV guests, as those can be operated > with existing backends without any problem, as long as those backends > are running in dom0. > > Per default allow virtio devices without grant support for non-PV > guests. > > Add a new config item to always force use of grants for virtio. > > Fixes: fa1f57421e0b ("xen/virtio: Enable restricted memory access using Xen grant mappings") > Reported-by: Viresh Kumar <viresh.kumar@linaro.org> > Signed-off-by: Juergen Gross <jgross@suse.com> > --- > V2: > - remove command line parameter (Christoph Hellwig) > --- > drivers/xen/Kconfig | 9 +++++++++ > include/xen/xen.h | 2 +- > 2 files changed, 10 insertions(+), 1 deletion(-) > > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig > index bfd5f4f706bc..a65bd92121a5 100644 > --- a/drivers/xen/Kconfig > +++ b/drivers/xen/Kconfig > @@ -355,4 +355,13 @@ config XEN_VIRTIO > > If in doubt, say n. > > +config XEN_VIRTIO_FORCE_GRANT > + bool "Require Xen virtio support to use grants" > + depends on XEN_VIRTIO > + help > + Require virtio for Xen guests to use grant mappings. > + This will avoid the need to give the backend the right to map all > + of the guest memory. This will need support on the backend side > + (e.g. qemu or kernel, depending on the virtio device types used). > + > endmenu > diff --git a/include/xen/xen.h b/include/xen/xen.h > index 0780a81e140d..4d4188f20337 100644 > --- a/include/xen/xen.h > +++ b/include/xen/xen.h > @@ -56,7 +56,7 @@ extern u64 xen_saved_max_mem_size; > > static inline void xen_set_restricted_virtio_memory_access(void) > { > - if (IS_ENABLED(CONFIG_XEN_VIRTIO) && xen_domain()) > + if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT) || xen_pv_domain()) > platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
Looks like, the flag will be *always* set for paravirtualized guests even if CONFIG_XEN_VIRTIO disabled.
Maybe we should clarify the check?
if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT) || IS_ENABLED(CONFIG_XEN_VIRTIO) && xen_pv_domain())
platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
> } >
-- Regards,
Oleksandr Tyshchenko
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