- Apr 21, 2022
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Tom Lendacky authored
During patch review, it was decided the SNP guest driver name should not be SEV-SNP specific, but should be generic for use with anything SEV. However, this feedback was missed and the driver name, and many of the driver functions and structures, are SEV-SNP name specific. Rename the driver to "sev-guest" (to match the misc device that is created) and update some of the function and structure names, too. While in the file, adjust the one pr_err() message to be a dev_err() message so that the message, if issued, uses the driver name. Signed-off-by:
Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by:
Borislav Petkov <bp@suse.de> Link: https://lore.kernel.org/r/307710bb5515c9088a19fd0b930268c7300479b2.1650464054.git.thomas.lendacky@amd.com
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Michael Roth authored
The helpers in arch/x86/boot/compressed/efi.c might be used during early boot to access the EFI system/config tables, and in some cases these EFI helpers might attempt to print debug/error messages, before console_init() has been called. __putstr() checks some variables to avoid printing anything before the console has been initialized, but this isn't enough since those variables live in .bss, which may not have been cleared yet. This can lead to a triple-fault occurring, primarily when booting in legacy/CSM mode (where EFI helpers will attempt to print some debug messages). Fix this by declaring these globals in .data section instead so there is no dependency on .bss being cleared before accessing them. Fixes: c01fce9c ("x86/compressed: Add SEV-SNP feature detection/setup") Reported-by:
Michael Roth <michael.roth@amd.com> Signed-off-by:
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- Apr 18, 2022
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Borislav Petkov authored
Copy the needed symbols only and remove the kernel proper includes. No functional changes. Signed-off-by:
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- Apr 14, 2022
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Haowen Bai authored
The function enc_payload() is wrongly declared bool but returns an integer value. Correct it. [ bp: Massage commit message. ] Fixes: fce96cf0 ("virt: Add SEV-SNP guest driver") Signed-off-by:
Haowen Bai <baihaowen@meizu.com> Signed-off-by:
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- Apr 11, 2022
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Yang Yingliang authored
If alloc_pages() fails, it returns a NULL pointer. Replace the wrong IS_ERR() check with the proper NULL pointer check. Fixes: fce96cf0 ("virt: Add SEV-SNP guest driver") Reported-by:
Hulk Robot <hulkci@huawei.com> Signed-off-by:
Yang Yingliang <yangyingliang@huawei.com> Signed-off-by:
Brijesh Singh <brijesh.singh@amd.com> Link: https://lore.kernel.org/r/20220411111213.1477853-1-yangyingliang@huawei.com
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- Apr 08, 2022
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Peter Gonda authored
Replace the halt loop in handle_vc_boot_ghcb() with an sev_es_terminate(). The HLT gives the system no indication the guest is unhappy. The termination request will signal there was an error during VC handling during boot. [ bp: Update it to pass the reason set too. ] Signed-off-by:
Peter Gonda <pgonda@google.com> Signed-off-by:
Joerg Roedel <jroedel@suse.de> Link: https://lore.kernel.org/r/20220317211913.1397427-1-pgonda@google.com
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- Apr 07, 2022
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Michael Roth authored
Update the documentation with information regarding SEV-SNP CPUID Enforcement details and what sort of assurances it provides to guests. Signed-off-by:
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Brijesh Singh authored
Version 2 of GHCB specification defines Non-Automatic-Exit (NAE) to get extended guest report which is similar to the SNP_GET_REPORT ioctl. The main difference is related to the additional data that will be returned. That additional data returned is a certificate blob that can be used by the SNP guest user. The certificate blob layout is defined in the GHCB specification. The driver simply treats the blob as a opaque data and copies it to userspace. [ bp: Massage commit message, cast 1st arg of access_ok() ] Signed-off-by:
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Brijesh Singh authored
The SNP_GET_DERIVED_KEY ioctl interface can be used by the SNP guest to ask the firmware to provide a key derived from a root key. The derived key may be used by the guest for any purposes it chooses, such as a sealing key or communicating with the external entities. See SEV-SNP firmware spec for more information. [ bp: No need to memset "req" - it will get overwritten. ] Signed-off-by:
Liam Merwick <liam.merwick@oracle.com> Link: https://lore.kernel.org/r/20220307213356.2797205-45-brijesh.singh@amd.com
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Brijesh Singh authored
The SEV-SNP specification provides the guest a mechanism to communicate with the PSP without risk from a malicious hypervisor who wishes to read, alter, drop or replay the messages sent. The driver uses snp_issue_guest_request() to issue GHCB SNP_GUEST_REQUEST or SNP_EXT_GUEST_REQUEST NAE events to submit the request to PSP. The PSP requires that all communication should be encrypted using key specified through a struct snp_guest_platform_data descriptor. Userspace can use SNP_GET_REPORT ioctl() to query the guest attestation report. See SEV-SNP spec section Guest Messages for more details. [ bp: Remove the "what" from the commit message, massage. ] Signed-off-by:
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Brijesh Singh authored
Version 2 of the GHCB specification provides a Non Automatic Exit (NAE) event type that can be used by the SEV-SNP guest to communicate with the PSP without risk from a malicious hypervisor who wishes to read, alter, drop or replay the messages sent. SNP_LAUNCH_UPDATE can insert two special pages into the guest’s memory: the secrets page and the CPUID page. The PSP firmware populates the contents of the secrets page. The secrets page contains encryption keys used by the guest to interact with the firmware. Because the secrets page is encrypted with the guest’s memory encryption key, the hypervisor cannot read the keys. See SEV-SNP firmware spec for further details on the secrets page format. Create a platform device that the SEV-SNP guest driver can bind to get the platform resources such as encryption key and message id to use to communicate with the PSP. The SEV-SNP guest driver provides a userspace interface to get the attestation report, key derivation, extended attestation report etc. Signed-off-by:
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Brijesh Singh authored
Version 2 of GHCB specification provides SNP_GUEST_REQUEST and SNP_EXT_GUEST_REQUEST NAE that can be used by the SNP guest to communicate with the PSP. While at it, add a snp_issue_guest_request() helper that will be used by driver or other subsystem to issue the request to PSP. See SEV-SNP firmware and GHCB spec for more details. Signed-off-by:
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Michael Roth authored
For debugging purposes it is very useful to have a way to see the full contents of the SNP CPUID table provided to a guest. Add an sev=debug kernel command-line option to do so. Also introduce some infrastructure so that additional options can be specified via sev=option1[,option2] over time in a consistent manner. [ bp: Massage, simplify string parsing. ] Suggested-by:
Borislav Petkov <bp@alien8.de> Signed-off-by:
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Michael Roth authored
SEV-SNP guests will be provided the location of special 'secrets' and 'CPUID' pages via the Confidential Computing blob. This blob is provided to the run-time kernel either through a boot_params field that was initialized by the boot/compressed kernel, or via a setup_data structure as defined by the Linux Boot Protocol. Locate the Confidential Computing blob from these sources and, if found, use the provided CPUID page/table address to create a copy that the run-time kernel will use when servicing CPUID instructions via a #VC handler. Signed-off-by:
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Michael Roth authored
Initial/preliminary detection of SEV-SNP is done via the Confidential Computing blob. Check for it prior to the normal SEV/SME feature initialization, and add some sanity checks to confirm it agrees with SEV-SNP CPUID/MSR bits. Signed-off-by:
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Michael Roth authored
The run-time kernel will need to access the Confidential Computing blob very early during boot to access the CPUID table it points to. At that stage, it will be relying on the identity-mapped page table set up by the boot/compressed kernel, so make sure the blob and the CPUID table it points to are mapped in advance. [ bp: Massage. ] Signed-off-by:
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Michael Roth authored
SEV-specific code will need to add some additional mappings, but doing this within ident_map_64.c requires some SEV-specific helpers to be exported and some SEV-specific struct definitions to be pulled into ident_map_64.c. Instead, export add_identity_map() so SEV-specific (and other subsystem-specific) code can be better contained outside of ident_map_64.c. While at it, rename the function to kernel_add_identity_map(), similar to the kernel_ident_mapping_init() function it relies upon. No functional changes. Suggested-by:
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Michael Roth authored
SEV-SNP guests will be provided the location of special 'secrets' 'CPUID' pages via the Confidential Computing blob. This blob is provided to the boot kernel either through an EFI config table entry, or via a setup_data structure as defined by the Linux Boot Protocol. Locate the Confidential Computing from these sources and, if found, use the provided CPUID page/table address to create a copy that the boot kernel will use when servicing CPUID instructions via a #VC CPUID handler. [ bp: s/cpuid/CPUID/ ] Signed-off-by:
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Michael Roth authored
Initial/preliminary detection of SEV-SNP is done via the Confidential Computing blob. Check for it prior to the normal SEV/SME feature initialization, and add some sanity checks to confirm it agrees with SEV-SNP CPUID/MSR bits. Signed-off-by:
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Michael Roth authored
The previously defined Confidential Computing blob is provided to the kernel via a setup_data structure or EFI config table entry. Currently, these are both checked for by boot/compressed kernel to access the CPUID table address within it for use with SEV-SNP CPUID enforcement. To also enable that enforcement for the run-time kernel, similar access to the CPUID table is needed early on while it's still using the identity-mapped page table set up by boot/compressed, where global pointers need to be accessed via fixup_pointer(). This isn't much of an issue for accessing setup_data, and the EFI config table helper code currently used in boot/compressed *could* be used in this case as well since they both rely on identity-mapping. However, it has some reliance on EFI helpers/string constants that would need to be accessed via fixup_pointer(), and fixing it up while making it shareable between boot/compressed and run-time kernel is fragile and introduces a good bit of ugliness. Instead, add a boot_params->cc_blob_address pointer that the boot/compressed kernel can initialize so that the run-time kernel can access the CC blob from there instead of re-scanning the EFI config table. Also document these in Documentation/x86/zero-page.rst. While there, add missing documentation for the acpi_rsdp_addr field, which serves a similar purpose in providing the run-time kernel a pointer to the ACPI RSDP table so that it does not need to [re-]scan the EFI configuration table. [ bp: Fix typos, massage commit message. ] Signed-off-by:
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Michael Roth authored
CPUID instructions generate a #VC exception for SEV-ES/SEV-SNP guests, for which early handlers are currently set up to handle. In the case of SEV-SNP, guests can use a configurable location in guest memory that has been pre-populated with a firmware-validated CPUID table to look up the relevant CPUID values rather than requesting them from hypervisor via a VMGEXIT. Add the various hooks in the #VC handlers to allow CPUID instructions to be handled via the table. The code to actually configure/enable the table will be added in a subsequent commit. Signed-off-by:
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Michael Roth authored
This code will also be used later for SEV-SNP-validated CPUID code in some cases, so move it to a common helper. While here, also add a check to terminate in cases where the CPUID function/subfunction is indexed and the subfunction is non-zero, since the GHCB MSR protocol does not support non-zero subfunctions. Suggested-by:
Sean Christopherson <seanjc@google.com> Signed-off-by:
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Michael Roth authored
Determining which CPUID leafs have significant ECX/index values is also needed by guest kernel code when doing SEV-SNP-validated CPUID lookups. Move this to common code to keep future updates in sync. Signed-off-by:
Venu Busireddy <venu.busireddy@oracle.com> Link: https://lore.kernel.org/r/20220307213356.2797205-31-brijesh.singh@amd.com
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Brijesh Singh authored
While launching encrypted guests, the hypervisor may need to provide some additional information during the guest boot. When booting under an EFI-based BIOS, the EFI configuration table contains an entry for the confidential computing blob that contains the required information. To support booting encrypted guests on non-EFI VMs, the hypervisor needs to pass this additional information to the guest kernel using a different method. For this purpose, introduce SETUP_CC_BLOB type in setup_data to hold the physical address of the confidential computing blob location. The boot loader or hypervisor may choose to use this method instead of an EFI configuration table. The CC blob location scanning should give preference to a setup_data blob over an EFI configuration table. In AMD SEV-SNP, the CC blob contains the address of the secrets and CPUID pages. The secrets page includes information such as a VM to PSP communication key and the CPUID page contains PSP-filtered CPUID values. Define the AMD SEV confidential computing blob structure. While at it, define the EFI GUID for the confidential computing blob. [ bp: Massage commit message, mark struct __packed. ] Signed-off-by:
Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20220307213356.2797205-30-brijesh.singh@amd.com
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- Apr 06, 2022
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Michael Roth authored
Future patches for SEV-SNP-validated CPUID will also require early parsing of the EFI configuration. Incrementally move the related code into a set of helpers that can be re-used for that purpose. In this instance, the current acpi.c kexec handling is mainly used to get the alternative EFI config table address provided by kexec via a setup_data entry of type SETUP_EFI. If not present, the code then falls back to normal EFI config table address provided by EFI system table. This would need to be done by all call-sites attempting to access the EFI config table, so just have efi_get_conf_table() handle that automatically. Signed-off-by:
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Michael Roth authored
Future patches for SEV-SNP-validated CPUID will also require early parsing of the EFI configuration. Incrementally move the related code into a set of helpers that can be re-used for that purpose. [ bp: Unbreak unnecessarily broken lines. ] Signed-off-by:
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Michael Roth authored
Future patches for SEV-SNP-validated CPUID will also require early parsing of the EFI configuration. Incrementally move the related code into a set of helpers that can be re-used for that purpose. [ bp: Remove superfluous zeroing of a stack variable. ] Signed-off-by:
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Michael Roth authored
Future patches for SEV-SNP-validated CPUID will also require early parsing of the EFI configuration. Incrementally move the related code into a set of helpers that can be re-used for that purpose. Signed-off-by:
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Michael Roth authored
Future patches for SEV-SNP-validated CPUID will also require early parsing of the EFI configuration. Incrementally move the related code into a set of helpers that can be re-used for that purpose. First, carve out the functionality which determines the EFI environment type the machine is booting on. [ bp: Massage commit message. ] Signed-off-by:
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Michael Roth authored
Due to 103a4908 ("x86/head/64: Disable stack protection for head$(BITS).o") kernel/head{32,64}.c are compiled with -fno-stack-protector to allow a call to set_bringup_idt_handler(), which would otherwise have stack protection enabled with CONFIG_STACKPROTECTOR_STRONG. While sufficient for that case, there may still be issues with calls to any external functions that were compiled with stack protection enabled that in-turn make stack-protected calls, or if the exception handlers set up by set_bringup_idt_handler() make calls to stack-protected functions. Subsequent patches for SEV-SNP CPUID validation support will introduce both such cases. Attempting to disable stack protection for everything in scope to address that is prohibitive since much of the code, like the SEV-ES #VC handler, is shared code that remains in use after boot and could benefit from having stack protection enabled. Attempting to inline calls is brittle and can quickly balloon out to library/helper code where that's not really an option. Instead, re-enable stack protection for head32.c/head64.c, and make the appropriate changes to ensure the segment used for the stack canary is initialized in advance of any stack-protected C calls. For head64.c: - The BSP will enter from startup_64() and call into C code (startup_64_setup_env()) shortly after setting up the stack, which may result in calls to stack-protected code. Set up %gs early to allow for this safely. - APs will enter from secondary_startup_64*(), and %gs will be set up soon after. There is one call to C code prior to %gs being setup (__startup_secondary_64()), but it is only to fetch 'sme_me_mask' global, so just load 'sme_me_mask' directly instead, and remove the now-unused __startup_secondary_64() function. For head32.c: - BSPs/APs will set %fs to __BOOT_DS prior to any C calls. In recent kernels, the compiler is configured to access the stack canary at %fs:__stack_chk_guard [1], which overlaps with the initial per-cpu '__stack_chk_guard' variable in the initial/"master" .data..percpu area. This is sufficient to allow access to the canary for use during initial startup, so no changes are needed there. [1] 3fb0fdb3 ("x86/stackprotector/32: Make the canary into a regular percpu variable") [ bp: Massage commit message. ] Suggested-by: Joerg Roedel <jroedel@suse.de> #for 64-bit %gs set up Signed-off-by:
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Tom Lendacky authored
To provide a more secure way to start APs under SEV-SNP, use the SEV-SNP AP Creation NAE event. This allows for guest control over the AP register state rather than trusting the hypervisor with the SEV-ES Jump Table address. During native_smp_prepare_cpus(), invoke an SEV-SNP function that, if SEV-SNP is active, will set/override apic->wakeup_secondary_cpu. This will allow the SEV-SNP AP Creation NAE event method to be used to boot the APs. As a result of installing the override when SEV-SNP is active, this method of starting the APs becomes the required method. The override function will fail to start the AP if the hypervisor does not have support for AP creation. [ bp: Work in forgotten review comments. ] Signed-off-by:
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Brijesh Singh authored
Add the needed functionality to change pages state from shared to private and vice-versa using the Page State Change VMGEXIT as documented in the GHCB spec. Signed-off-by:
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Brijesh Singh authored
probe_roms() accesses the memory range (0xc0000 - 0x10000) to probe various ROMs. The memory range is not part of the E820 system RAM range. The memory range is mapped as private (i.e encrypted) in the page table. When SEV-SNP is active, all the private memory must be validated before accessing. The ROM range was not part of E820 map, so the guest BIOS did not validate it. An access to invalidated memory will cause a exception yet, so validate the ROM memory regions before it is accessed. [ bp: Massage commit message. ] Signed-off-by:
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Brijesh Singh authored
The encryption attribute for the .bss..decrypted section is cleared in the initial page table build. This is because the section contains the data that need to be shared between the guest and the hypervisor. When SEV-SNP is active, just clearing the encryption attribute in the page table is not enough. The page state needs to be updated in the RMP table. Signed-off-by:
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Brijesh Singh authored
early_set_memory_{encrypted,decrypted}() are used for changing the page state from decrypted (shared) to encrypted (private) and vice versa. When SEV-SNP is active, the page state transition needs to go through additional steps. If the page is transitioned from shared to private, then perform the following after the encryption attribute is set in the page table: 1. Issue the page state change VMGEXIT to add the page as a private in the RMP table. 2. Validate the page after its successfully added in the RMP table. To maintain the security guarantees, if the page is transitioned from private to shared, then perform the following before clearing the encryption attribute from the page table. 1. Invalidate the page. 2. Issue the page state change VMGEXIT to make the page shared in the RMP table. early_set_memory_{encrypted,decrypted}() can be called before the GHCB is setup so use the SNP page state MSR protocol VMGEXIT defined in the GHCB specification to request the page state change in the RMP table. While at it, add a helper snp_prep_memory() which will be used in probe_roms(), in a later patch. [ bp: Massage commit message. ] Signed-off-by: -
Brijesh Singh authored
The SEV-SNP guest is required by the GHCB spec to register the GHCB's Guest Physical Address (GPA). This is because the hypervisor may prefer that a guest uses a consistent and/or specific GPA for the GHCB associated with a vCPU. For more information, see the GHCB specification section "GHCB GPA Registration". [ bp: Cleanup comments. ] Signed-off-by:
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Brijesh Singh authored
The SEV-SNP guest is required by the GHCB spec to register the GHCB's Guest Physical Address (GPA). This is because the hypervisor may prefer that a guest use a consistent and/or specific GPA for the GHCB associated with a vCPU. For more information, see the GHCB specification section "GHCB GPA Registration". If hypervisor can not work with the guest provided GPA then terminate the guest boot. Signed-off-by:
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Brijesh Singh authored
Many of the integrity guarantees of SEV-SNP are enforced through the Reverse Map Table (RMP). Each RMP entry contains the GPA at which a particular page of DRAM should be mapped. The VMs can request the hypervisor to add pages in the RMP table via the Page State Change VMGEXIT defined in the GHCB specification. Inside each RMP entry is a Validated flag; this flag is automatically cleared to 0 by the CPU hardware when a new RMP entry is created for a guest. Each VM page can be either validated or invalidated, as indicated by the Validated flag in the RMP entry. Memory access to a private page that is not validated generates a #VC. A VM must use the PVALIDATE instruction to validate a private page before using it. To maintain the security guarantee of SEV-SNP guests, when transitioning pages from private to shared, the guest must invalidate the pages before asking the hypervisor to change the page state to shared in the RMP table. After the pages are mapped private in the page table, the guest must issue a page state change VMGEXIT to mark the pages private in the RMP table and validate them. Upon boot, BIOS should have validated the entire system memory. During the kernel decompression stage, early_setup_ghcb() uses set_page_decrypted() to make the GHCB page shared (i.e. clear encryption attribute). And while exiting from the decompression, it calls set_page_encrypted() to make the page private. Add snp_set_page_{private,shared}() helpers that are used by set_page_{decrypted,encrypted}() to change the page state in the RMP table. [ bp: Massage commit message and comments. ] Signed-off-by: -
Brijesh Singh authored
The Virtual Machine Privilege Level (VMPL) feature in the SEV-SNP architecture allows a guest VM to divide its address space into four levels. The level can be used to provide hardware isolated abstraction layers within a VM. VMPL0 is the highest privilege level, and VMPL3 is the least privilege level. Certain operations must be done by the VMPL0 software, such as: * Validate or invalidate memory range (PVALIDATE instruction) * Allocate VMSA page (RMPADJUST instruction when VMSA=1) The initial SNP support requires that the guest kernel is running at VMPL0. Add such a check to verify the guest is running at level 0 before continuing the boot. There is no easy method to query the current VMPL level, so use the RMPADJUST instruction to determine whether the guest is running at the VMPL0. [ bp: Massage commit message. ] Signed-off-by:
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Brijesh Singh authored
An SNP-active guest uses the PVALIDATE instruction to validate or rescind the validation of a guest page’s RMP entry. Upon completion, a return code is stored in EAX and rFLAGS bits are set based on the return code. If the instruction completed successfully, the carry flag (CF) indicates if the content of the RMP were changed or not. See AMD APM Volume 3 for additional details. Signed-off-by:
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