[PATCH v2 0/3] x86: Fix SEV guest regression

From: Brijesh Singh
Date: Tue Aug 28 2018 - 18:13:15 EST

The following commit

x86/kvmclock: Remove memblock dependency


introduced SEV guest regression.

The guest physical address holding the wall_clock and hv_clock_boot
are shared with the hypervisor must be mapped with C=0 when SEV
is active. To clear the C-bit we use kernel_physical_mapping_init() to
split the large pages. The above commit moved the kvmclock initialization
very early and kernel_physical_mapping_init() fails to allocate memory
while spliting the large page.

To solve it, we add a special .data..decrypted section, this section can be
used to hold the shared variables. Early boot code maps this section with
C=0. The section is pmd aligned and sized to avoid the need to split the pages.
Caller can use __decrypted attribute to add the variables in .data..decrypted

Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Cc: "Radim KrÄmÃÅ" <rkrcmar@xxxxxxxxxx>

Changes since v1:
- move the logic to re-arrange mapping in new patch
- move the definition of __start_data_* in mem_encrypt.h
- map the workarea buffer as encrypted when SEV is enabled
- enhance the sme_populate_pgd to update the pte/pmd flags when mapping exist

Brijesh Singh (3):
x86/mm: Restructure sme_encrypt_kernel()
x86/mm: add .data..decrypted section to hold shared variables
x86/kvm: use __decrypted attribute when declaring shared variables

arch/x86/include/asm/mem_encrypt.h | 6 +
arch/x86/kernel/head64.c | 9 ++
arch/x86/kernel/kvmclock.c | 30 ++++-
arch/x86/kernel/vmlinux.lds.S | 17 +++
arch/x86/mm/mem_encrypt_identity.c | 232 +++++++++++++++++++++++++++----------
5 files changed, 227 insertions(+), 67 deletions(-)