Re: [PATCH v3 3/3] xen: don't require virtio with grants for non-PV guests
From: Oleksandr
Date: Wed Jun 22 2022 - 05:03:45 EST
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@xxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
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