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x86/virtio: Have SEV guests enforce restricted virtio memory access 

An SEV guest requires that virtio devices use the DMA API to allow the
hypervisor to successfully access guest memory as needed.

The VIRTIO_F_VERSION_1 and VIRTIO_F_ACCESS_PLATFORM features tell virtio
to use the DMA API. Add arch_has_restricted_virtio_memory_access() for
x86, to fail the device probe if these features have not been set for the
device when running as an SEV guest.

 [ bp: Fix -Wmissing-prototypes warning
   Reported-by: kernel test robot <lkp@intel.com> ]

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/b46e0211f77ca1831f11132f969d470a6ffc9267.1614897610.git.thomas.lendacky@amd.com
This commit is contained in:
Tom Lendacky 2021-03-04 16:40:11 -06:00 committed by Borislav Petkov
parent f3db3365c0
commit 229164175f
2 changed files with 7 additions and 0 deletions
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1
arch/x86/Kconfig
View File

@ -1518,6 +1518,7 @@ config AMD_MEM_ENCRYPT
select ARCH_USE_MEMREMAP_PROT
select ARCH_HAS_FORCE_DMA_UNENCRYPTED
select INSTRUCTION_DECODER
select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
help
Say yes to enable support for the encryption of system memory.
This requires an AMD processor that supports Secure Memory

6
arch/x86/mm/mem_encrypt.c
View File

@ -19,6 +19,7 @@
#include <linux/kernel.h>
#include <linux/bitops.h>
#include <linux/dma-mapping.h>
#include <linux/virtio_config.h>
#include <asm/tlbflush.h>
#include <asm/fixmap.h>
@ -484,3 +485,8 @@ void __init mem_encrypt_init(void)
print_mem_encrypt_feature_info();
}
int arch_has_restricted_virtio_memory_access(void)
{
return sev_active();
}
EXPORT_SYMBOL_GPL(arch_has_restricted_virtio_memory_access);