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Message-ID: <a8ce8ad3-aa3b-ea87-34cf-6532a272e9d8@gmail.com>
Date: Wed, 22 Jun 2022 12:03:25 +0300
From: Oleksandr <olekstysh@...il.com>
To: Juergen Gross <jgross@...e.com>, xen-devel@...ts.xenproject.org,
x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Stefano Stabellini <sstabellini@...nel.org>,
Russell King <linux@...linux.org.uk>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
linux-arm-kernel@...ts.infradead.org,
Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH v3 3/3] xen: don't require virtio with grants for non-PV
guests
On 22.06.22 09:38, 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.
>
> On Arm require VIRTIO_F_ACCESS_PLATFORM for devices having been listed
> in the device tree to use grants.
>
> 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@...aro.org>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
> V2:
> - remove command line parameter (Christoph Hellwig)
> V3:
> - rebase to callback method
Patch looks good, just one NIT ...
> ---
> arch/arm/xen/enlighten.c | 4 +++-
> arch/x86/xen/enlighten_hvm.c | 4 +++-
> arch/x86/xen/enlighten_pv.c | 5 ++++-
> drivers/xen/Kconfig | 9 +++++++++
> drivers/xen/grant-dma-ops.c | 10 ++++++++++
> include/xen/xen-ops.h | 6 ++++++
> include/xen/xen.h | 8 --------
> 7 files changed, 35 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 1f9c3ba32833..93c8ccbf2982 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -34,6 +34,7 @@
> #include <linux/timekeeping.h>
> #include <linux/timekeeper_internal.h>
> #include <linux/acpi.h>
> +#include <linux/virtio_anchor.h>
>
> #include <linux/mm.h>
>
> @@ -443,7 +444,8 @@ static int __init xen_guest_init(void)
> if (!xen_domain())
> return 0;
>
> - xen_set_restricted_virtio_memory_access();
> + if (IS_ENABLED(CONFIG_XEN_VIRTIO))
> + virtio_set_mem_acc_cb(xen_virtio_mem_acc);
>
> if (!acpi_disabled)
> xen_acpi_guest_init();
> diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
> index 8b71b1dd7639..28762f800596 100644
> --- a/arch/x86/xen/enlighten_hvm.c
> +++ b/arch/x86/xen/enlighten_hvm.c
> @@ -4,6 +4,7 @@
> #include <linux/cpu.h>
> #include <linux/kexec.h>
> #include <linux/memblock.h>
> +#include <linux/virtio_anchor.h>
>
> #include <xen/features.h>
> #include <xen/events.h>
> @@ -195,7 +196,8 @@ static void __init xen_hvm_guest_init(void)
> if (xen_pv_domain())
> return;
>
> - xen_set_restricted_virtio_memory_access();
> + if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
> + virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
>
> init_hvm_pv_info();
>
> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
> index e3297b15701c..5aaae8a77f55 100644
> --- a/arch/x86/xen/enlighten_pv.c
> +++ b/arch/x86/xen/enlighten_pv.c
> @@ -31,6 +31,7 @@
> #include <linux/gfp.h>
> #include <linux/edd.h>
> #include <linux/reboot.h>
> +#include <linux/virtio_anchor.h>
>
> #include <xen/xen.h>
> #include <xen/events.h>
> @@ -109,7 +110,9 @@ static DEFINE_PER_CPU(struct tls_descs, shadow_tls_desc);
>
> static void __init xen_pv_init_platform(void)
> {
> - xen_set_restricted_virtio_memory_access();
> + /* PV guests can't operate virtio devices without grants. */
> + if (IS_ENABLED(CONFIG_XEN_VIRTIO))
> + virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
>
> populate_extra_pte(fix_to_virt(FIX_PARAVIRT_BOOTMAP));
>
> 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/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
> index fc0142484001..8973fc1e9ccc 100644
> --- a/drivers/xen/grant-dma-ops.c
> +++ b/drivers/xen/grant-dma-ops.c
> @@ -12,6 +12,8 @@
> #include <linux/of.h>
> #include <linux/pfn.h>
> #include <linux/xarray.h>
> +#include <linux/virtio_anchor.h>
> +#include <linux/virtio.h>
> #include <xen/xen.h>
> #include <xen/xen-ops.h>
> #include <xen/grant_table.h>
> @@ -287,6 +289,14 @@ bool xen_is_grant_dma_device(struct device *dev)
> return has_iommu;
> }
>
> +bool xen_virtio_mem_acc(struct virtio_device *dev)
> +{
> + if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
> + return true;
> +
> + return xen_is_grant_dma_device(dev->dev.parent);
> +}
... I am thinking would it be better to move this to xen/xen-ops.h
as grant-dma-ops.c is generic (not only for virtio, although the virtio
is the first use-case)
diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
index 8973fc1..fc01424 100644
--- a/drivers/xen/grant-dma-ops.c
+++ b/drivers/xen/grant-dma-ops.c
@@ -12,8 +12,6 @@
#include <linux/of.h>
#include <linux/pfn.h>
#include <linux/xarray.h>
-#include <linux/virtio_anchor.h>
-#include <linux/virtio.h>
#include <xen/xen.h>
#include <xen/xen-ops.h>
#include <xen/grant_table.h>
@@ -289,14 +287,6 @@ bool xen_is_grant_dma_device(struct device *dev)
return has_iommu;
}
-bool xen_virtio_mem_acc(struct virtio_device *dev)
-{
- if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
- return true;
-
- return xen_is_grant_dma_device(dev->dev.parent);
-}
-
void xen_grant_setup_dma_ops(struct device *dev)
{
struct xen_grant_dma_data *data;
diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index 98c399a..a9ae51b 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -6,6 +6,7 @@
#include <linux/notifier.h>
#include <linux/efi.h>
#include <linux/virtio_anchor.h>
+#include <linux/virtio.h>
#include <xen/features.h>
#include <asm/xen/interface.h>
#include <xen/interface/vcpu.h>
@@ -218,7 +219,13 @@ static inline void xen_preemptible_hcall_end(void) { }
#ifdef CONFIG_XEN_GRANT_DMA_OPS
void xen_grant_setup_dma_ops(struct device *dev);
bool xen_is_grant_dma_device(struct device *dev);
-bool xen_virtio_mem_acc(struct virtio_device *dev);
+static inline bool xen_virtio_mem_acc(struct virtio_device *dev)
+{
+ if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
+ return true;
+
+ return xen_is_grant_dma_device(dev->dev.parent);
+}
#else
static inline void xen_grant_setup_dma_ops(struct device *dev)
{
> +
> void xen_grant_setup_dma_ops(struct device *dev)
> {
> struct xen_grant_dma_data *data;
> diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
> index 80546960f8b7..98c399a960a3 100644
> --- a/include/xen/xen-ops.h
> +++ b/include/xen/xen-ops.h
> @@ -5,6 +5,7 @@
> #include <linux/percpu.h>
> #include <linux/notifier.h>
> #include <linux/efi.h>
> +#include <linux/virtio_anchor.h>
> #include <xen/features.h>
> #include <asm/xen/interface.h>
> #include <xen/interface/vcpu.h>
> @@ -217,6 +218,7 @@ static inline void xen_preemptible_hcall_end(void) { }
> #ifdef CONFIG_XEN_GRANT_DMA_OPS
> void xen_grant_setup_dma_ops(struct device *dev);
> bool xen_is_grant_dma_device(struct device *dev);
> +bool xen_virtio_mem_acc(struct virtio_device *dev);
> #else
> static inline void xen_grant_setup_dma_ops(struct device *dev)
> {
> @@ -225,6 +227,10 @@ static inline bool xen_is_grant_dma_device(struct device *dev)
> {
> return false;
> }
> +static inline bool xen_virtio_mem_acc(struct virtio_device *dev)
> +{
> + return false;
> +}
> #endif /* CONFIG_XEN_GRANT_DMA_OPS */
>
> #endif /* INCLUDE_XEN_OPS_H */
> diff --git a/include/xen/xen.h b/include/xen/xen.h
> index ac5a144c6a65..a99bab817523 100644
> --- a/include/xen/xen.h
> +++ b/include/xen/xen.h
> @@ -52,14 +52,6 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
> extern u64 xen_saved_max_mem_size;
> #endif
>
> -#include <linux/virtio_anchor.h>
> -
> -static inline void xen_set_restricted_virtio_memory_access(void)
> -{
> - if (IS_ENABLED(CONFIG_XEN_VIRTIO) && xen_domain())
> - virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
> -}
> -
> #ifdef CONFIG_XEN_UNPOPULATED_ALLOC
> int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages);
> void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages);
--
Regards,
Oleksandr Tyshchenko
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