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Subject[PATCH v3 0/5] x86/sev-es: Mitigate some HV attack vectors
From: Joerg Roedel <>


here are some enhancements to the SEV(-ES) code in the Linux kernel to
self-protect it against some newly detected hypervisor attacks. There
are 3 attacks addressed here:

1) Hypervisor does not present the SEV-enabled bit via CPUID

2) The Hypervisor presents the wrong C-bit position via CPUID

3) An encrypted RAM page is mapped as MMIO in the nested
page-table, causing #VC exceptions and possible leak of the
data to the hypervisor or data/code injection from the

The attacks are described in more detail in this paper:

Please review.



Changes to v2:

- Use %r8/%r9 to modify %cr4 in sev_verify_cbit()
and return the new page-table pointer in that function.

Changes to v1:

- Disable CR4.PGE during C-bit test

- Do not safe/restore caller-safed registers in

Joerg Roedel (5):
x86/boot/compressed/64: Introduce sev_status
x86/boot/compressed/64: Add CPUID sanity check to early #VC handler
x86/boot/compressed/64: Check SEV encryption in 64-bit boot-path
x86/head/64: Check SEV encryption before switching to kernel
x86/sev-es: Do not support MMIO to/from encrypted memory

arch/x86/boot/compressed/ident_map_64.c | 1 +
arch/x86/boot/compressed/mem_encrypt.S | 14 +++-
arch/x86/boot/compressed/misc.h | 2 +
arch/x86/kernel/head_64.S | 12 ++++
arch/x86/kernel/sev-es-shared.c | 26 +++++++
arch/x86/kernel/sev-es.c | 20 ++++--
arch/x86/kernel/sev_verify_cbit.S | 90 +++++++++++++++++++++++++
arch/x86/mm/mem_encrypt.c | 1 +
8 files changed, 158 insertions(+), 8 deletions(-)
create mode 100644 arch/x86/kernel/sev_verify_cbit.S


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