user/sven/linux.git/tools/arch, branch v5.19.8

x86/speculation: Add RSB VM Exit protections

2022-08-11T11:22:05Z

commit 2b1299322016731d56807aa49254a5ea3080b6b3 upstream. tl;dr: The Enhanced IBRS mitigation for Spectre v2 does not work as documented for RET instructions after VM exits. Mitigate it with a new one-entry RSB stuffing mechanism and a new LFENCE. == Background == Indirect Branch Restricted Speculation (IBRS) was designed to help mitigate Branch Target Injection and Speculative Store Bypass, i.e. Spectre, attacks. IBRS prevents software run in less privileged modes from affecting branch prediction in more privileged modes. IBRS requires the MSR to be written on every privilege level change. To overcome some of the performance issues of IBRS, Enhanced IBRS was introduced. eIBRS is an "always on" IBRS, in other words, just turn it on once instead of writing the MSR on every privilege level change. When eIBRS is enabled, more privileged modes should be protected from less privileged modes, including protecting VMMs from guests. == Problem == Here's a simplification of how guests are run on Linux' KVM: void run_kvm_guest(void) { // Prepare to run guest VMRESUME(); // Clean up after guest runs } The execution flow for that would look something like this to the processor: 1. Host-side: call run_kvm_guest() 2. Host-side: VMRESUME 3. Guest runs, does "CALL guest_function" 4. VM exit, host runs again 5. Host might make some "cleanup" function calls 6. Host-side: RET from run_kvm_guest() Now, when back on the host, there are a couple of possible scenarios of post-guest activity the host needs to do before executing host code: * on pre-eIBRS hardware (legacy IBRS, or nothing at all), the RSB is not touched and Linux has to do a 32-entry stuffing. * on eIBRS hardware, VM exit with IBRS enabled, or restoring the host IBRS=1 shortly after VM exit, has a documented side effect of flushing the RSB except in this PBRSB situation where the software needs to stuff the last RSB entry "by hand". IOW, with eIBRS supported, host RET instructions should no longer be influenced by guest behavior after the host retires a single CALL instruction. However, if the RET instructions are "unbalanced" with CALLs after a VM exit as is the RET in #6, it might speculatively use the address for the instruction after the CALL in #3 as an RSB prediction. This is a problem since the (untrusted) guest controls this address. Balanced CALL/RET instruction pairs such as in step #5 are not affected. == Solution == The PBRSB issue affects a wide variety of Intel processors which support eIBRS. But not all of them need mitigation. Today, X86_FEATURE_RSB_VMEXIT triggers an RSB filling sequence that mitigates PBRSB. Systems setting RSB_VMEXIT need no further mitigation - i.e., eIBRS systems which enable legacy IBRS explicitly. However, such systems (X86_FEATURE_IBRS_ENHANCED) do not set RSB_VMEXIT and most of them need a new mitigation. Therefore, introduce a new feature flag X86_FEATURE_RSB_VMEXIT_LITE which triggers a lighter-weight PBRSB mitigation versus RSB_VMEXIT. The lighter-weight mitigation performs a CALL instruction which is immediately followed by a speculative execution barrier (INT3). This steers speculative execution to the barrier -- just like a retpoline -- which ensures that speculation can never reach an unbalanced RET. Then, ensure this CALL is retired before continuing execution with an LFENCE. In other words, the window of exposure is opened at VM exit where RET behavior is troublesome. While the window is open, force RSB predictions sampling for RET targets to a dead end at the INT3. Close the window with the LFENCE. There is a subset of eIBRS systems which are not vulnerable to PBRSB. Add these systems to the cpu_vuln_whitelist[] as NO_EIBRS_PBRSB. Future systems that aren't vulnerable will set ARCH_CAP_PBRSB_NO. [ bp: Massage, incorporate review comments from Andy Cooper. ] Signed-off-by: Daniel Sneddon Co-developed-by: Pawan Gupta Signed-off-by: Pawan Gupta Signed-off-by: Borislav Petkov Signed-off-by: Greg Kroah-Hartman

tools headers cpufeatures: Sync with the kernel sources

2022-07-27T14:17:50Z

To pick the changes from: 28a99e95f55c6185 ("x86/amd: Use IBPB for firmware calls") This only causes these perf files to be rebuilt: CC /tmp/build/perf/bench/mem-memcpy-x86-64-asm.o CC /tmp/build/perf/bench/mem-memset-x86-64-asm.o And addresses this perf build warning: Warning: Kernel ABI header at 'tools/arch/x86/include/asm/cpufeatures.h' differs from latest version at 'arch/x86/include/asm/cpufeatures.h' diff -u tools/arch/x86/include/asm/cpufeatures.h arch/x86/include/asm/cpufeatures.h Cc: Adrian Hunter Cc: Borislav Petkov Cc: Ian Rogers Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra

tools arch x86: Sync the msr-index.h copy with the kernel sources

2022-07-17T13:50:50Z

To pick up the changes from these csets: 4ad3278df6fe2b08 ("x86/speculation: Disable RRSBA behavior") d7caac991feeef1b ("x86/cpu/amd: Add Spectral Chicken") That cause no changes to tooling: $ tools/perf/trace/beauty/tracepoints/x86_msr.sh > before $ cp arch/x86/include/asm/msr-index.h tools/arch/x86/include/asm/msr-index.h $ tools/perf/trace/beauty/tracepoints/x86_msr.sh > after $ diff -u before after $ Just silences this perf build warning: Warning: Kernel ABI header at 'tools/arch/x86/include/asm/msr-index.h' differs from latest version at 'arch/x86/include/asm/msr-index.h' diff -u tools/arch/x86/include/asm/msr-index.h arch/x86/include/asm/msr-index.h Cc: Adrian Hunter Cc: Borislav Petkov Cc: Ian Rogers Cc: Jiri Olsa Cc: Namhyung Kim Cc: Pawan Gupta Cc: Peter Zijlstra Link: https://lore.kernel.org/lkml/YtQTm9wsB3hxQWvy@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools headers cpufeatures: Sync with the kernel sources

2022-07-17T13:49:14Z

To pick the changes from: f43b9876e857c739 ("x86/retbleed: Add fine grained Kconfig knobs") a149180fbcf336e9 ("x86: Add magic AMD return-thunk") 15e67227c49a5783 ("x86: Undo return-thunk damage") 369ae6ffc41a3c11 ("x86/retpoline: Cleanup some #ifdefery") 4ad3278df6fe2b08 x86/speculation: Disable RRSBA behavior 26aae8ccbc197223 x86/cpu/amd: Enumerate BTC_NO 9756bba28470722d x86/speculation: Fill RSB on vmexit for IBRS 3ebc170068885b6f x86/bugs: Add retbleed=ibpb 2dbb887e875b1de3 x86/entry: Add kernel IBRS implementation 6b80b59b35557065 x86/bugs: Report AMD retbleed vulnerability a149180fbcf336e9 x86: Add magic AMD return-thunk 15e67227c49a5783 x86: Undo return-thunk damage a883d624aed463c8 x86/cpufeatures: Move RETPOLINE flags to word 11 51802186158c74a0 x86/speculation/mmio: Enumerate Processor MMIO Stale Data bug This only causes these perf files to be rebuilt: CC /tmp/build/perf/bench/mem-memcpy-x86-64-asm.o CC /tmp/build/perf/bench/mem-memset-x86-64-asm.o And addresses this perf build warning: Warning: Kernel ABI header at 'tools/arch/x86/include/asm/cpufeatures.h' differs from latest version at 'arch/x86/include/asm/cpufeatures.h' diff -u tools/arch/x86/include/asm/cpufeatures.h arch/x86/include/asm/cpufeatures.h Warning: Kernel ABI header at 'tools/arch/x86/include/asm/disabled-features.h' differs from latest version at 'arch/x86/include/asm/disabled-features.h' diff -u tools/arch/x86/include/asm/disabled-features.h arch/x86/include/asm/disabled-features.h Cc: Adrian Hunter Cc: Borislav Petkov Cc: Ian Rogers Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra

Merge tag 'x86_bugs_retbleed' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-07-12T01:15:25Z

Pull x86 retbleed fixes from Borislav Petkov: "Just when you thought that all the speculation bugs were addressed and solved and the nightmare is complete, here's the next one: speculating after RET instructions and leaking privileged information using the now pretty much classical covert channels. It is called RETBleed and the mitigation effort and controlling functionality has been modelled similar to what already existing mitigations provide" * tag 'x86_bugs_retbleed' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits) x86/speculation: Disable RRSBA behavior x86/kexec: Disable RET on kexec x86/bugs: Do not enable IBPB-on-entry when IBPB is not supported x86/entry: Move PUSH_AND_CLEAR_REGS() back into error_entry x86/bugs: Add Cannon lake to RETBleed affected CPU list x86/retbleed: Add fine grained Kconfig knobs x86/cpu/amd: Enumerate BTC_NO x86/common: Stamp out the stepping madness KVM: VMX: Prevent RSB underflow before vmenter x86/speculation: Fill RSB on vmexit for IBRS KVM: VMX: Fix IBRS handling after vmexit KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS KVM: VMX: Convert launched argument to flags KVM: VMX: Flatten __vmx_vcpu_run() objtool: Re-add UNWIND_HINT_{SAVE_RESTORE} x86/speculation: Remove x86_spec_ctrl_mask x86/speculation: Use cached host SPEC_CTRL value for guest entry/exit x86/speculation: Fix SPEC_CTRL write on SMT state change x86/speculation: Fix firmware entry SPEC_CTRL handling x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n ...

x86/speculation: Disable RRSBA behavior

2022-07-09T11:12:45Z

Some Intel processors may use alternate predictors for RETs on RSB-underflow. This condition may be vulnerable to Branch History Injection (BHI) and intramode-BTI. Kernel earlier added spectre_v2 mitigation modes (eIBRS+Retpolines, eIBRS+LFENCE, Retpolines) which protect indirect CALLs and JMPs against such attacks. However, on RSB-underflow, RET target prediction may fallback to alternate predictors. As a result, RET's predicted target may get influenced by branch history. A new MSR_IA32_SPEC_CTRL bit (RRSBA_DIS_S) controls this fallback behavior when in kernel mode. When set, RETs will not take predictions from alternate predictors, hence mitigating RETs as well. Support for this is enumerated by CPUID.7.2.EDX[RRSBA_CTRL] (bit2). For spectre v2 mitigation, when a user selects a mitigation that protects indirect CALLs and JMPs against BHI and intramode-BTI, set RRSBA_DIS_S also to protect RETs for RSB-underflow case. Signed-off-by: Pawan Gupta Signed-off-by: Borislav Petkov

tools kvm headers arm64: Update KVM headers from the kernel sources

2022-06-28T14:56:01Z

To pick the changes from: 2cde51f1e10f2600 ("KVM: arm64: Hide KVM_REG_ARM_*_BMAP_BIT_COUNT from userspace") b22216e1a617ca55 ("KVM: arm64: Add vendor hypervisor firmware register") 428fd6788d4d0e0d ("KVM: arm64: Add standard hypervisor firmware register") 05714cab7d63b189 ("KVM: arm64: Setup a framework for hypercall bitmap firmware registers") 18f3976fdb5da2ba ("KVM: arm64: uapi: Add kvm_debug_exit_arch.hsr_high") a5905d6af492ee6a ("KVM: arm64: Allow SMCCC_ARCH_WORKAROUND_3 to be discovered and migrated") That don't causes any changes in tooling (when built on x86), only addresses this perf build warning: Warning: Kernel ABI header at 'tools/arch/arm64/include/uapi/asm/kvm.h' differs from latest version at 'arch/arm64/include/uapi/asm/kvm.h' diff -u tools/arch/arm64/include/uapi/asm/kvm.h arch/arm64/include/uapi/asm/kvm.h Cc: Adrian Hunter Cc: Alexandru Elisei Cc: Catalin Marinas Cc: Ian Rogers Cc: James Morse Cc: Jiri Olsa Cc: Marc Zyngier Cc: Namhyung Kim Cc: Raghavendra Rao Ananta Link: https://lore.kernel.org/lkml/YrsWcDQyJC+xsfmm@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools headers UAPI: Synch KVM's svm.h header with the kernel

2022-06-26T15:32:55Z

To pick up the changes from: d5af44dde5461d12 ("x86/sev: Provide support for SNP guest request NAEs") 0afb6b660a6b58cb ("x86/sev: Use SEV-SNP AP creation to start secondary CPUs") dc3f3d2474b80eae ("x86/mm: Validate memory when changing the C-bit") cbd3d4f7c4e5a93e ("x86/sev: Check SEV-SNP features support") That gets these new SVM exit reasons: + { SVM_VMGEXIT_PSC, "vmgexit_page_state_change" }, \ + { SVM_VMGEXIT_GUEST_REQUEST, "vmgexit_guest_request" }, \ + { SVM_VMGEXIT_EXT_GUEST_REQUEST, "vmgexit_ext_guest_request" }, \ + { SVM_VMGEXIT_AP_CREATION, "vmgexit_ap_creation" }, \ + { SVM_VMGEXIT_HV_FEATURES, "vmgexit_hypervisor_feature" }, \ Addressing this perf build warning: Warning: Kernel ABI header at 'tools/arch/x86/include/uapi/asm/svm.h' differs from latest version at 'arch/x86/include/uapi/asm/svm.h' diff -u tools/arch/x86/include/uapi/asm/svm.h arch/x86/include/uapi/asm/svm.h This causes these changes: CC /tmp/build/perf-urgent/arch/x86/util/kvm-stat.o LD /tmp/build/perf-urgent/arch/x86/util/perf-in.o LD /tmp/build/perf-urgent/arch/x86/perf-in.o LD /tmp/build/perf-urgent/arch/perf-in.o LD /tmp/build/perf-urgent/perf-in.o LINK /tmp/build/perf-urgent/perf Cc: Adrian Hunter Cc: Borislav Petkov Cc: Brijesh Singh Cc: Ian Rogers Cc: Jiri Olsa Cc: Namhyung Kim Cc: Tom Lendacky Signed-off-by: Arnaldo Carvalho de Melo

tools headers cpufeatures: Sync with the kernel sources

2022-06-26T15:32:43Z

To pick the changes from: d6d0c7f681fda1d0 ("x86/cpufeatures: Add PerfMonV2 feature bit") 296d5a17e793956f ("KVM: SEV-ES: Use V_TSC_AUX if available instead of RDTSC/MSR_TSC_AUX intercepts") f30903394eb62316 ("x86/cpufeatures: Add virtual TSC_AUX feature bit") 8ad7e8f696951f19 ("x86/fpu/xsave: Support XSAVEC in the kernel") 59bd54a84d15e933 ("x86/tdx: Detect running as a TDX guest in early boot") a77d41ac3a0f41c8 ("x86/cpufeatures: Add AMD Fam19h Branch Sampling feature") This only causes these perf files to be rebuilt: CC /tmp/build/perf/bench/mem-memcpy-x86-64-asm.o CC /tmp/build/perf/bench/mem-memset-x86-64-asm.o And addresses this perf build warning: Warning: Kernel ABI header at 'tools/arch/x86/include/asm/cpufeatures.h' differs from latest version at 'arch/x86/include/asm/cpufeatures.h' diff -u tools/arch/x86/include/asm/cpufeatures.h arch/x86/include/asm/cpufeatures.h Warning: Kernel ABI header at 'tools/arch/x86/include/asm/disabled-features.h' differs from latest version at 'arch/x86/include/asm/disabled-features.h' diff -u tools/arch/x86/include/asm/disabled-features.h arch/x86/include/asm/disabled-features.h Cc: Peter Zijlstra Cc: Sandipan Das Cc: Babu Moger Cc: Paolo Bonzini Cc: Thomas Gleixner Cc: Dave Hansen Cc: Kuppuswamy Sathyanarayanan Cc: Stephane Eranian Cc: Peter Zijlstra Link: https://lore.kernel.org/lkml/YrDkgmwhLv+nKeOo@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools headers arm64: Sync arm64's cputype.h with the kernel sources

2022-06-19T14:23:04Z

To get the changes in: cae889302ebf5a9b ("KVM: arm64: vgic-v3: List M1 Pro/Max as requiring the SEIS workaround") That addresses this perf build warning: Warning: Kernel ABI header at 'tools/arch/arm64/include/asm/cputype.h' differs from latest version at 'arch/arm64/include/asm/cputype.h' diff -u tools/arch/arm64/include/asm/cputype.h arch/arm64/include/asm/cputype.h Cc: Marc Zyngier Link: https://lore.kernel.org/lkml/Yq8w7p4omYKNwOij@kernel.org Signed-off-by: Arnaldo Carvalho de Melo