In TDX guests, by default memory is protected from host access. If a
guest needs to communicate with the VMM (like the I/O use case), it uses
a single bit in the physical address to communicate the protected/shared
attribute of the given page.
In the x86 ARCH code, __PHYSICAL_MASK macro represents the width of the
physical address in the given architecture. It is used in creating
physical PAGE_MASK for address bits in the kernel. Since in TDX guest,
a single bit is used as metadata, it needs to be excluded from valid
physical address bits to avoid using incorrect addresses bits in the
kernel.
Enable DYNAMIC_PHYSICAL_MASK to support updating the __PHYSICAL_MASK.
Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20220405232939.73860-6-kirill.shutemov@linux.intel.com
Confidential Computing (CC) features (like string I/O unroll support,
memory encryption/decryption support, etc) are conditionally enabled
in the kernel using cc_platform_has() API. Since TDX guests also need
to use these CC features, extend cc_platform_has() API and add TDX
guest-specific CC attributes support.
CC API also provides an interface to deal with encryption mask. Extend
it to cover TDX.
Details about which bit in the page table entry to be used to indicate
shared/private state is determined by using the TDINFO TDCALL.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20220405232939.73860-5-kirill.shutemov@linux.intel.com
Guests communicate with VMMs with hypercalls. Historically, these
are implemented using instructions that are known to cause VMEXITs
like VMCALL, VMLAUNCH, etc. However, with TDX, VMEXITs no longer
expose the guest state to the host. This prevents the old hypercall
mechanisms from working. So, to communicate with VMM, TDX
specification defines a new instruction called TDCALL.
In a TDX based VM, since the VMM is an untrusted entity, an intermediary
layer -- TDX module -- facilitates secure communication between the host
and the guest. TDX module is loaded like a firmware into a special CPU
mode called SEAM. TDX guests communicate with the TDX module using the
TDCALL instruction.
A guest uses TDCALL to communicate with both the TDX module and VMM.
The value of the RAX register when executing the TDCALL instruction is
used to determine the TDCALL type. A leaf of TDCALL used to communicate
with the VMM is called TDVMCALL.
Add generic interfaces to communicate with the TDX module and VMM
(using the TDCALL instruction).
__tdx_module_call() - Used to communicate with the TDX module (via
TDCALL instruction).
__tdx_hypercall() - Used by the guest to request services from
the VMM (via TDVMCALL leaf of TDCALL).
Also define an additional wrapper _tdx_hypercall(), which adds error
handling support for the TDCALL failure.
The __tdx_module_call() and __tdx_hypercall() helper functions are
implemented in assembly in a .S file. The TDCALL ABI requires
shuffling arguments in and out of registers, which proved to be
awkward with inline assembly.
Just like syscalls, not all TDVMCALL use cases need to use the same
number of argument registers. The implementation here picks the current
worst-case scenario for TDCALL (4 registers). For TDCALLs with fewer
than 4 arguments, there will end up being a few superfluous (cheap)
instructions. But, this approach maximizes code reuse.
For registers used by the TDCALL instruction, please check TDX GHCI
specification, the section titled "TDCALL instruction" and "TDG.VP.VMCALL
Interface".
Based on previous patch by Sean Christopherson.
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20220405232939.73860-4-kirill.shutemov@linux.intel.com
In preparation of extending cc_platform_has() API to support TDX guest,
use CPUID instruction to detect support for TDX guests in the early
boot code (via tdx_early_init()). Since copy_bootdata() is the first
user of cc_platform_has() API, detect the TDX guest status before it.
Define a synthetic feature flag (X86_FEATURE_TDX_GUEST) and set this
bit in a valid TDX guest platform.
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20220405232939.73860-2-kirill.shutemov@linux.intel.com
The CC_ATTR_GUEST_SEV_SNP can be used by the guest to query whether the
SNP (Secure Nested Paging) feature is active.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-10-brijesh.singh@amd.com
AMD SME/SEV uses a bit in the page table entries to indicate that the
page is encrypted and not accessible to the VMM.
TDX uses a similar approach, but the polarity of the mask is opposite to
AMD: if the bit is set the page is accessible to VMM.
Provide vendor-neutral API to deal with the mask: cc_mkenc() and
cc_mkdec() modify given address to make it encrypted/decrypted. It can
be applied to phys_addr_t, pgprotval_t or page table entry value.
pgprot_encrypted() and pgprot_decrypted() reimplemented using new
helpers.
The implementation will be extended to cover TDX.
pgprot_decrypted() is used by drivers (i915, virtio_gpu, vfio).
cc_mkdec() called by pgprot_decrypted(). Export cc_mkdec().
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20220222185740.26228-5-kirill.shutemov@linux.intel.com
The kernel derives the confidential computing platform
type it is running as from sme_me_mask on AMD or by using
hv_is_isolation_supported() on HyperV isolation VMs. This detection
process will be more complicated as more platforms get added.
Declare a confidential computing vendor variable explicitly and set it
via cc_set_vendor() on the respective platform.
[ bp: Massage commit message, fixup HyperV check. ]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20220222185740.26228-4-kirill.shutemov@linux.intel.com
Move cc_platform.c to arch/x86/coco/. The directory is going to be the
home space for code related to confidential computing.
Intel TDX code will land here. AMD SEV code will also eventually be
moved there.
No functional changes.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20220222185740.26228-3-kirill.shutemov@linux.intel.com
