- Sep 11, 2020
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Tom Lendacky authored
Calling down to EFI runtime services can result in the firmware performing VMGEXIT calls. The firmware is likely to use the GHCB of the OS (e.g., for setting EFI variables), so each GHCB in the system needs to be identity-mapped in the EFI page tables, as unencrypted, to avoid page faults. Signed-off-by:
Tom Lendacky <thomas.lendacky@amd.com> [ jroedel@suse.de: Moved GHCB mapping loop to sev-es.c ] Signed-off-by:
Joerg Roedel <jroedel@suse.de> Signed-off-by:
Borislav Petkov <bp@suse.de> Acked-by:
Ard Biesheuvel <ardb@kernel.org> Link: https://lkml.kernel.org/r/20200907131613.12703-72-joro@8bytes.org
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- Sep 10, 2020
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Joerg Roedel authored
When running under SEV-ES, the kernel has to tell the hypervisor when to open the NMI window again after an NMI was injected. This is done with an NMI-complete message to the hypervisor. Add code to the kernel's NMI handler to send this message right at the beginning of do_nmi(). This always allows nesting NMIs. [ bp: Mark __sev_es_nmi_complete() noinstr: vmlinux.o: warning: objtool: exc_nmi()+0x17: call to __sev_es_nmi_complete() leaves .noinstr.text section While at it, use __pa_nodebug() for the same reason due to CONFIG_DEBUG_VIRTUAL=y: vmlinux.o: warning: objtool: __sev_es_nmi_complete()+0xd9: call to __phys_addr() leaves .noinstr.text section ] Signed-off-by:
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- Sep 09, 2020
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Joerg Roedel authored
Add a play_dead handler when running under SEV-ES. This is needed because the hypervisor can't deliver an SIPI request to restart the AP. Instead, the kernel has to issue a VMGEXIT to halt the VCPU until the hypervisor wakes it up again. Signed-off-by:
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Joerg Roedel authored
The APs are not ready to handle exceptions when verify_cpu() is called in secondary_startup_64(). Signed-off-by:
Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/20200907131613.12703-69-joro@8bytes.org
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Joerg Roedel authored
The IDT on 64-bit contains vectors which use paranoid_entry() and/or IST stacks. To make these vectors work, the TSS and the getcpu GDT entry need to be set up before the IDT is loaded. Signed-off-by:
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Tom Lendacky authored
As part of the GHCB specification, the booting of APs under SEV-ES requires an AP jump table when transitioning from one layer of code to another (e.g. when going from UEFI to the OS). As a result, each layer that parks an AP must provide the physical address of an AP jump table to the next layer via the hypervisor. Upon booting of the kernel, read the AP jump table address from the hypervisor. Under SEV-ES, APs are started using the INIT-SIPI-SIPI sequence. Before issuing the first SIPI request for an AP, the start CS and IP is programmed into the AP jump table. Upon issuing the SIPI request, the AP will awaken and jump to that start CS:IP address. Signed-off-by:
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Joerg Roedel authored
The code at the trampoline entry point is executed in real-mode. In real-mode, #VC exceptions can't be handled so anything that might cause such an exception must be avoided. In the standard trampoline entry code this is the WBINVD instruction and the call to verify_cpu(), which are both not needed anyway when running as an SEV-ES guest. Signed-off-by:
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Doug Covelli authored
Add VMware-specific handling for #VC faults caused by VMMCALL instructions. Signed-off-by:
Doug Covelli <dcovelli@vmware.com> Signed-off-by:
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Tom Lendacky authored
Implement the callbacks to copy the processor state required by KVM to the GHCB. Signed-off-by:
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Joerg Roedel authored
Add two new paravirt callbacks to provide hypervisor-specific processor state in the GHCB and to copy state from the hypervisor back to the processor. Signed-off-by:
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Joerg Roedel authored
Handle #VC exceptions caused by #DB exceptions in the guest. Those must be handled outside of instrumentation_begin()/end() so that the handler will not be raised recursively. Handle them by calling the kernel's debug exception handler. Signed-off-by:
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Joerg Roedel authored
Implement a handler for #VC exceptions caused by #AC exceptions. The #AC exception is just forwarded to do_alignment_check() and not pushed down to the hypervisor, as requested by the SEV-ES GHCB Standardization Specification. Signed-off-by:
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Tom Lendacky authored
Implement a handler for #VC exceptions caused by VMMCALL instructions. This is only a starting point, VMMCALL emulation under SEV-ES needs further hypervisor-specific changes to provide additional state. [ bp: Drop "this patch". ] Signed-off-by:
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Tom Lendacky authored
Implement a handler for #VC exceptions caused by MWAIT and MWAITX instructions. Signed-off-by:
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Tom Lendacky authored
Implement a handler for #VC exceptions caused by MONITOR and MONITORX instructions. Signed-off-by:
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Tom Lendacky authored
Implement a handler for #VC exceptions caused by INVD instructions. Since Linux should never use INVD, just mark it as unsupported. Signed-off-by:
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Tom Lendacky authored
Implement a handler for #VC exceptions caused by RDPMC instructions. Signed-off-by:
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Tom Lendacky authored
Implement a handler for #VC exceptions caused by RDTSC and RDTSCP instructions. Also make it available in the pre-decompression stage because the KASLR code uses RDTSC/RDTSCP to gather entropy and some hypervisors intercept these instructions. Signed-off-by:
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Tom Lendacky authored
Implement a handler for #VC exceptions caused by WBINVD instructions. Signed-off-by:
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Tom Lendacky authored
Add code to handle #VC exceptions on DR7 register reads and writes. This is needed early because show_regs() reads DR7 to print it out. Under SEV-ES, there is currently no support for saving/restoring the DRx registers but software expects to be able to write to the DR7 register. For now, cache the value written to DR7 and return it on read attempts, but do not touch the real hardware DR7. Signed-off-by:
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Tom Lendacky authored
Implement a handler for #VC exceptions caused by RDMSR/WRMSR instructions. Signed-off-by:
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Joerg Roedel authored
Add handling for emulation of the MOVS instruction on MMIO regions, as done by the memcpy_toio() and memcpy_fromio() functions. Signed-off-by:
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Tom Lendacky authored
Add a handler for #VC exceptions caused by MMIO intercepts. These intercepts come along as nested page faults on pages with reserved bits set. Signed-off-by:
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Joerg Roedel authored
When a #VC exception is triggered by user-space, the instruction decoder needs to read the instruction bytes from user addresses. Enhance vc_decode_insn() to safely fetch kernel and user instructions. Signed-off-by:
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Joerg Roedel authored
Re-use the handlers for CPUID- and IOIO-caused #VC exceptions in the early boot handler. Signed-off-by:
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Tom Lendacky authored
Add the handlers for #VC exceptions invoked at runtime. Signed-off-by:
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Joerg Roedel authored
The #VC handler needs special entry code because: 1. It runs on an IST stack 2. It needs to be able to handle nested #VC exceptions To make this work, the entry code is implemented to pretend it doesn't use an IST stack. When entered from user-mode or early SYSCALL entry path it switches to the task stack. If entered from kernel-mode it tries to switch back to the previous stack in the IRET frame. The stack found in the IRET frame is validated first, and if it is not safe to use it for the #VC handler, the code will switch to a fall-back stack (the #VC2 IST stack). From there, it can cause nested exceptions again. Signed-off-by:
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Joerg Roedel authored
The get_stack_info() functionality is needed in the entry code for the #VC exception handler. Provide a version of it in the .text.noinstr section which can be called safely from there. Signed-off-by:
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Joerg Roedel authored
When an NMI hits in the #VC handler entry code before it has switched to another stack, any subsequent #VC exception in the NMI code-path will overwrite the interrupted #VC handler's stack. Make sure this doesn't happen by explicitly adjusting the #VC IST entry in the NMI handler for the time it can cause #VC exceptions. [ bp: Touchups, spelling fixes. ] Signed-off-by:
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Joerg Roedel authored
Allocate and map an IST stack and an additional fall-back stack for the #VC handler. The memory for the stacks is allocated only when SEV-ES is active. The #VC handler needs to use an IST stack because a #VC exception can be raised from kernel space with unsafe stack, e.g. in the SYSCALL entry path. Since the #VC exception can be nested, the #VC handler switches back to the interrupted stack when entered from kernel space. If switching back is not possible, the fall-back stack is used. Signed-off-by:
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Tom Lendacky authored
The runtime handler needs one GHCB per-CPU. Set them up and map them unencrypted. [ bp: Touchups and simplification. ] Signed-off-by:
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Joerg Roedel authored
Add the infrastructure to handle #VC exceptions when the kernel runs on virtual addresses and has mapped a GHCB. This handler will be used until the runtime #VC handler takes over. Since the handler runs very early, disable instrumentation for sev-es.c. [ bp: Make vc_ghcb_invalidate() __always_inline so that it can be inlined in noinstr functions like __sev_es_nmi_complete(). ] Signed-off-by:
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Joerg Roedel authored
Setup an early handler for #VC exceptions. There is no GHCB mapped yet, so just re-use the vc_no_ghcb_handler(). It can only handle CPUID exit-codes, but that should be enough to get the kernel through verify_cpu() and __startup_64() until it runs on virtual addresses. Signed-off-by:
kernel test robot <lkp@intel.com> Link: https://lkml.kernel.org/r/20200908123517.GA3764@8bytes.org
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Joerg Roedel authored
Setup sev-es.c and include the code from the pre-decompression stage to also build it into the image of the running kernel. Temporarily add __maybe_unused annotations to avoid build warnings until the functions get used. [ bp: Use the non-tracing rd/wrmsr variants because: vmlinux.o: warning: objtool: __sev_es_nmi_complete()+0x11f: \ call to do_trace_write_msr() leaves .noinstr.text section as __sev_es_nmi_complete() is noinstr due to being called from the NMI handler exc_nmi(). ] Signed-off-by:
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- Sep 08, 2020
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Joerg Roedel authored
Refactor the message printed to the kernel log which indicates whether SEV or SME, etc is active. This will scale better in the future when more memory encryption features might be added. Also add SEV-ES to the list of features. [ bp: Massage. ] Signed-off-by:
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Joerg Roedel authored
Add a sev_es_active() function for checking whether SEV-ES is enabled. Also cache the value of MSR_AMD64_SEV at boot to speed up the feature checking in the running code. [ bp: Remove "!!" in sev_active() too. ] Signed-off-by:
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Joerg Roedel authored
Move the assembly coded dispatch between page-faults and all other exceptions to C code to make it easier to maintain and extend. Also change the return-type of early_make_pgtable() to bool and make it static. Signed-off-by:
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Joerg Roedel authored
Move these two functions from kernel/idt.c to include/asm/desc.h: * init_idt_data() * idt_init_desc() These functions are needed to setup IDT entries very early and need to be called from head64.c. To be usable this early, these functions need to be compiled without instrumentation and the stack-protector feature. These features need to be kept enabled for kernel/idt.c, so head64.c must use its own versions. [ bp: Take Kees' suggested patch title and add his Rev-by. ] Signed-off-by:
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Joerg Roedel authored
Add a separate bringup IDT for the CPU bringup code that will be used until the kernel switches to the idt_table. There are two reasons for a separate IDT: 1) When the idt_table is set up and the secondary CPUs are booted, it contains entries (e.g. IST entries) which require certain CPU state to be set up. This includes a working TSS (for IST), MSR_GS_BASE (for stack protector) or CR4.FSGSBASE (for paranoid_entry) path. By using a dedicated IDT for early boot this state need not to be set up early. 2) The idt_table is static to idt.c, so any function using/modifying must be in idt.c too. That means that all compiler driven instrumentation like tracing or KASAN is also active in this code. But during early CPU bringup the environment is not set up for this instrumentation to work correctly. To avoid all of these hassles and make early exception handling robust, use a dedicated bringup IDT. The IDT is loaded two times, first on the boot CPU while the kernel is still running on direct mapped addresses, and again later after the switch to kernel addresses has happened. The second IDT load happens on the boot and secondary CPUs. Signed-off-by:
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Joerg Roedel authored
Make sure there is a stack once the kernel runs from virtual addresses. At this stage any secondary CPU which boots will have lost its stack because the kernel switched to a new page-table which does not map the real-mode stack anymore. This is needed for handling early #VC exceptions caused by instructions like CPUID. Signed-off-by:
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