Messages in this thread | | | Date | Thu, 16 Jun 2022 10:56:18 +0200 | Subject | Re: [PATCH v2] xen: don't require virtio with grants for non-PV guests | From | Juergen Gross <> |
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On 16.06.22 09:31, Oleksandr wrote: > > 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); >
Yes, we should. I had the function in grant-dma-ops.c in V1, and could drop the CONFIG_XEN_VIRTIO dependency for that reason.
I'll wait for more comments before sending V3, though.
Juergen [unhandled content-type:application/pgp-keys][unhandled content-type:application/pgp-signature] | |