linux-kernel - [PATCH v9 2/2] s390: virtio: PV needs VIRTIO I/O device protection

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Message-Id: <1597854198-2871-3-git-send-email-pmorel@linux.ibm.com>
Date:   Wed, 19 Aug 2020 18:23:18 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     pasic@...ux.ibm.com, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        mst@...hat.com, jasowang@...hat.com, cohuck@...hat.com,
        kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, thomas.lendacky@....com,
        david@...son.dropbear.id.au, linuxram@...ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com
Subject: [PATCH v9 2/2] s390: virtio: PV needs VIRTIO I/O device protection

If protected virtualization is active on s390, VIRTIO has retricted
access to the guest memory.
Define CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS and export
arch_has_restricted_virtio_memory_access to advertize VIRTIO if that's
the case, preventing a host error on access attempt.

Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
---
 arch/s390/Kconfig   |  1 +
 arch/s390/mm/init.c | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9cfd8de907cb..c12422c26389 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -820,6 +820,7 @@ menu "Virtualization"
 config PROTECTED_VIRTUALIZATION_GUEST
 	def_bool n
 	prompt "Protected virtualization guest support"
+	select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
 	help
 	  Select this option, if you want to be able to run this
 	  kernel as a protected virtualization KVM guest.
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 6dc7c3b60ef6..8febd73ed6ca 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -45,6 +45,7 @@
 #include <asm/kasan.h>
 #include <asm/dma-mapping.h>
 #include <asm/uv.h>
+#include <linux/virtio_config.h>
 
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
 
@@ -161,6 +162,16 @@ bool force_dma_unencrypted(struct device *dev)
 	return is_prot_virt_guest();
 }
 
+#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
+
+int arch_has_restricted_virtio_memory_access(void)
+{
+	return is_prot_virt_guest();
+}
+EXPORT_SYMBOL(arch_has_restricted_virtio_memory_access);
+
+#endif
+
 /* protected virtualization */
 static void pv_init(void)
 {
-- 
2.25.1