virtio: replace restricted mem access flag with callback

Instead of having a global flag to require restricted memory access
for all virtio devices, introduce a callback which can select that
requirement on a per-device basis.

For convenience add a common function returning always true, which can
be used for use cases like SEV.

Per default use a callback always returning false.

As the callback needs to be set in early init code already, add a
virtio anchor which is builtin in case virtio is enabled.

Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Arm64 guest using Xen
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/20220622063838.8854-2-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 6a0ac00..4a154a0 100644 (file)
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -31,7 +31,6 @@
 #include <linux/cma.h>
 #include <linux/gfp.h>
 #include <linux/dma-direct.h>
-#include <linux/platform-feature.h>
 #include <asm/processor.h>
 #include <linux/uaccess.h>
 #include <asm/pgalloc.h>
@@ -48,6 +47,7 @@
 #include <asm/kasan.h>
 #include <asm/dma-mapping.h>
 #include <asm/uv.h>
+#include <linux/virtio_anchor.h>
 #include <linux/virtio_config.h>
 
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(".bss..swapper_pg_dir");
@@ -175,7 +175,7 @@ static void pv_init(void)
        if (!is_prot_virt_guest())
                return;
 
-       platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
+       virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
 
        /* make sure bounce buffers are shared */
        swiotlb_init(true, SWIOTLB_FORCE | SWIOTLB_VERBOSE);

diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index f6d038e..9745268 100644 (file)
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -20,8 +20,8 @@
 #include <linux/bitops.h>
 #include <linux/dma-mapping.h>
 #include <linux/virtio_config.h>
+#include <linux/virtio_anchor.h>
 #include <linux/cc_platform.h>
-#include <linux/platform-feature.h>
 
 #include <asm/tlbflush.h>
 #include <asm/fixmap.h>
@@ -245,7 +245,7 @@ void __init sev_setup_arch(void)
        swiotlb_adjust_size(size);
 
        /* Set restricted memory access for virtio. */
-       platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
+       virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
 }
 
 static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index e1556d2..56c77f6 100644 (file)
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -1,6 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0-only
+config VIRTIO_ANCHOR
+       bool
+
 config VIRTIO
        tristate
+       select VIRTIO_ANCHOR
        help
          This option is selected by any driver which implements the virtio
          bus, such as CONFIG_VIRTIO_PCI, CONFIG_VIRTIO_MMIO, CONFIG_RPMSG

diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index 0a82d08..8e98d24 100644 (file)
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_VIRTIO) += virtio.o virtio_ring.o
+obj-$(CONFIG_VIRTIO_ANCHOR) += virtio_anchor.o
 obj-$(CONFIG_VIRTIO_PCI_LIB) += virtio_pci_modern_dev.o
 obj-$(CONFIG_VIRTIO_PCI_LIB_LEGACY) += virtio_pci_legacy_dev.o
 obj-$(CONFIG_VIRTIO_MMIO) += virtio_mmio.o

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 7deeed3..14c142d 100644 (file)
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -2,10 +2,10 @@
 #include <linux/virtio.h>
 #include <linux/spinlock.h>
 #include <linux/virtio_config.h>
+#include <linux/virtio_anchor.h>
 #include <linux/module.h>
 #include <linux/idr.h>
 #include <linux/of.h>
-#include <linux/platform-feature.h>
 #include <uapi/linux/virtio_ids.h>
 
 /* Unique numbering for virtio devices. */
@@ -174,7 +174,7 @@ static int virtio_features_ok(struct virtio_device *dev)
 
        might_sleep();
 
-       if (platform_has(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS)) {
+       if (virtio_check_mem_acc_cb(dev)) {
                if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
                        dev_warn(&dev->dev,
                                 "device must provide VIRTIO_F_VERSION_1\n");

diff --git a/drivers/virtio/virtio_anchor.c b/drivers/virtio/virtio_anchor.c
new file mode 100644 (file)
index 0000000..4d6a5d2
--- /dev/null
+++ b/drivers/virtio/virtio_anchor.c
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/virtio.h>
+#include <linux/virtio_anchor.h>
+
+bool virtio_require_restricted_mem_acc(struct virtio_device *dev)
+{
+       return true;
+}
+EXPORT_SYMBOL_GPL(virtio_require_restricted_mem_acc);
+
+static bool virtio_no_restricted_mem_acc(struct virtio_device *dev)
+{
+       return false;
+}
+
+bool (*virtio_check_mem_acc_cb)(struct virtio_device *dev) =
+       virtio_no_restricted_mem_acc;
+EXPORT_SYMBOL_GPL(virtio_check_mem_acc_cb);

diff --git a/include/linux/platform-feature.h b/include/linux/platform-feature.h
index b2f48be..6ed8599 100644 (file)
--- a/include/linux/platform-feature.h
+++ b/include/linux/platform-feature.h
@@ -6,11 +6,7 @@
 #include <asm/platform-feature.h>
 
 /* The platform features are starting with the architecture specific ones. */
-
-/* Used to enable platform specific DMA handling for virtio devices. */
-#define PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS  (0 + PLATFORM_ARCH_FEAT_N)
-
-#define PLATFORM_FEAT_N                                (1 + PLATFORM_ARCH_FEAT_N)
+#define PLATFORM_FEAT_N                                (0 + PLATFORM_ARCH_FEAT_N)
 
 void platform_set(unsigned int feature);
 void platform_clear(unsigned int feature);

diff --git a/include/linux/virtio_anchor.h b/include/linux/virtio_anchor.h
new file mode 100644 (file)
index 0000000..432e6c0
--- /dev/null
+++ b/include/linux/virtio_anchor.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_VIRTIO_ANCHOR_H
+#define _LINUX_VIRTIO_ANCHOR_H
+
+#ifdef CONFIG_VIRTIO_ANCHOR
+struct virtio_device;
+
+bool virtio_require_restricted_mem_acc(struct virtio_device *dev);
+extern bool (*virtio_check_mem_acc_cb)(struct virtio_device *dev);
+
+static inline void virtio_set_mem_acc_cb(bool (*func)(struct virtio_device *))
+{
+       virtio_check_mem_acc_cb = func;
+}
+#else
+#define virtio_set_mem_acc_cb(func) do { } while (0)
+#endif
+
+#endif /* _LINUX_VIRTIO_ANCHOR_H */

diff --git a/include/xen/xen.h b/include/xen/xen.h
index 0780a81..ac5a144 100644 (file)
--- a/include/xen/xen.h
+++ b/include/xen/xen.h
@@ -52,12 +52,12 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
 extern u64 xen_saved_max_mem_size;
 #endif
 
-#include <linux/platform-feature.h>
+#include <linux/virtio_anchor.h>
 
 static inline void xen_set_restricted_virtio_memory_access(void)
 {
        if (IS_ENABLED(CONFIG_XEN_VIRTIO) && xen_domain())
-               platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
+               virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
 }
 
 #ifdef CONFIG_XEN_UNPOPULATED_ALLOC