kernel.git/arch/x86/include/asm/processor.h, branch linux-4.19.y

x86: Move gds_ucode_mitigated() declaration to header

2023-08-16T16:13:00Z

commit eb3515dc99c7c85f4170b50838136b2a193f8012 upstream. The declaration got placed in the .c file of the caller, but that causes a warning for the definition: arch/x86/kernel/cpu/bugs.c:682:6: error: no previous prototype for 'gds_ucode_mitigated' [-Werror=missing-prototypes] Move it to a header where both sides can observe it instead. Fixes: 81ac7e5d74174 ("KVM: Add GDS_NO support to KVM") Signed-off-by: Arnd Bergmann Signed-off-by: Dave Hansen Tested-by: Daniel Sneddon Cc: stable@kernel.org Link: https://lore.kernel.org/all/20230809130530.1913368-2-arnd%40kernel.org Signed-off-by: Greg Kroah-Hartman

x86: Move TS_COMPAT back to asm/thread_info.h

2021-03-24T10:07:37Z

commit 66c1b6d74cd7035e85c426f0af4aede19e805c8a upstream. Move TS_COMPAT back to asm/thread_info.h, close to TS_I386_REGS_POKED. It was moved to asm/processor.h by b9d989c7218a ("x86/asm: Move the thread_info::status field to thread_struct"), then later 37a8f7c38339 ("x86/asm: Move 'status' from thread_struct to thread_info") moved the 'status' field back but TS_COMPAT was forgotten. Preparatory patch to fix the COMPAT case for get_nr_restart_syscall() Fixes: 609c19a385c8 ("x86/ptrace: Stop setting TS_COMPAT in ptrace code") Signed-off-by: Oleg Nesterov Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210201174649.GA17880@redhat.com Signed-off-by: Greg Kroah-Hartman

x86/entry: Increase entry_stack size to a full page

2020-07-16T06:17:23Z

[ Upstream commit c7aadc09321d8f9a1d3bd1e6d8a47222ecddf6c5 ] Marco crashed in bad_iret with a Clang11/KCSAN build due to overflowing the stack. Now that we run C code on it, expand it to a full page. Suggested-by: Andy Lutomirski Reported-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Lai Jiangshan Tested-by: Marco Elver Link: https://lkml.kernel.org/r/20200618144801.819246178@infradead.org Signed-off-by: Sasha Levin

x86/speculation/taa: Add mitigation for TSX Async Abort

2019-11-12T18:21:32Z

commit 1b42f017415b46c317e71d41c34ec088417a1883 upstream. TSX Async Abort (TAA) is a side channel vulnerability to the internal buffers in some Intel processors similar to Microachitectural Data Sampling (MDS). In this case, certain loads may speculatively pass invalid data to dependent operations when an asynchronous abort condition is pending in a TSX transaction. This includes loads with no fault or assist condition. Such loads may speculatively expose stale data from the uarch data structures as in MDS. Scope of exposure is within the same-thread and cross-thread. This issue affects all current processors that support TSX, but do not have ARCH_CAP_TAA_NO (bit 8) set in MSR_IA32_ARCH_CAPABILITIES. On CPUs which have their IA32_ARCH_CAPABILITIES MSR bit MDS_NO=0, CPUID.MD_CLEAR=1 and the MDS mitigation is clearing the CPU buffers using VERW or L1D_FLUSH, there is no additional mitigation needed for TAA. On affected CPUs with MDS_NO=1 this issue can be mitigated by disabling the Transactional Synchronization Extensions (TSX) feature. A new MSR IA32_TSX_CTRL in future and current processors after a microcode update can be used to control the TSX feature. There are two bits in that MSR: * TSX_CTRL_RTM_DISABLE disables the TSX sub-feature Restricted Transactional Memory (RTM). * TSX_CTRL_CPUID_CLEAR clears the RTM enumeration in CPUID. The other TSX sub-feature, Hardware Lock Elision (HLE), is unconditionally disabled with updated microcode but still enumerated as present by CPUID(EAX=7).EBX{bit4}. The second mitigation approach is similar to MDS which is clearing the affected CPU buffers on return to user space and when entering a guest. Relevant microcode update is required for the mitigation to work. More details on this approach can be found here: https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html The TSX feature can be controlled by the "tsx" command line parameter. If it is force-enabled then "Clear CPU buffers" (MDS mitigation) is deployed. The effective mitigation state can be read from sysfs. [ bp: - massage + comments cleanup - s/TAA_MITIGATION_TSX_DISABLE/TAA_MITIGATION_TSX_DISABLED/g - Josh. - remove partial TAA mitigation in update_mds_branch_idle() - Josh. - s/tsx_async_abort_cmdline/tsx_async_abort_parse_cmdline/g ] Signed-off-by: Pawan Gupta Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Reviewed-by: Josh Poimboeuf Signed-off-by: Greg Kroah-Hartman

x86/speculation/mds: Add mitigation mode VMWERV

2019-05-14T17:17:57Z

commit 22dd8365088b6403630b82423cf906491859b65e upstream In virtualized environments it can happen that the host has the microcode update which utilizes the VERW instruction to clear CPU buffers, but the hypervisor is not yet updated to expose the X86_FEATURE_MD_CLEAR CPUID bit to guests. Introduce an internal mitigation mode VMWERV which enables the invocation of the CPU buffer clearing even if X86_FEATURE_MD_CLEAR is not set. If the system has no updated microcode this results in a pointless execution of the VERW instruction wasting a few CPU cycles. If the microcode is updated, but not exposed to a guest then the CPU buffers will be cleared. That said: Virtual Machines Will Eventually Receive Vaccine Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov Reviewed-by: Jon Masters Tested-by: Jon Masters Signed-off-by: Greg Kroah-Hartman

x86/speculation/mds: Add mitigation control for MDS

2019-05-14T17:17:56Z

commit bc1241700acd82ec69fde98c5763ce51086269f8 upstream Now that the mitigations are in place, add a command line parameter to control the mitigation, a mitigation selector function and a SMT update mechanism. This is the minimal straight forward initial implementation which just provides an always on/off mode. The command line parameter is: mds=[full|off] This is consistent with the existing mitigations for other speculative hardware vulnerabilities. The idle invocation is dynamically updated according to the SMT state of the system similar to the dynamic update of the STIBP mitigation. The idle mitigation is limited to CPUs which are only affected by MSBDS and not any other variant, because the other variants cannot be mitigated on SMT enabled systems. Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov Reviewed-by: Jon Masters Tested-by: Jon Masters Signed-off-by: Greg Kroah-Hartman

x86/speculation/l1tf: Increase l1tf memory limit for Nehalem+

2018-08-27T08:29:14Z

On Nehalem and newer core CPUs the CPU cache internally uses 44 bits physical address space. The L1TF workaround is limited by this internal cache address width, and needs to have one bit free there for the mitigation to work. Older client systems report only 36bit physical address space so the range check decides that L1TF is not mitigated for a 36bit phys/32GB system with some memory holes. But since these actually have the larger internal cache width this warning is bogus because it would only really be needed if the system had more than 43bits of memory. Add a new internal x86_cache_bits field. Normally it is the same as the physical bits field reported by CPUID, but for Nehalem and newerforce it to be at least 44bits. Change the L1TF memory size warning to use the new cache_bits field to avoid bogus warnings and remove the bogus comment about memory size. Fixes: 17dbca119312 ("x86/speculation/l1tf: Add sysfs reporting for l1tf") Reported-by: George Anchev Reported-by: Christopher Snowhill Signed-off-by: Andi Kleen Signed-off-by: Thomas Gleixner Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org Cc: Michael Hocko Cc: vbabka@suse.cz Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180824170351.34874-1-andi@firstfloor.org

x86/speculation/l1tf: Fix off-by-one error when warning that system has too much RAM

2018-08-24T07:51:14Z

Two users have reported [1] that they have an "extremely unlikely" system with more than MAX_PA/2 memory and L1TF mitigation is not effective. In fact it's a CPU with 36bits phys limit (64GB) and 32GB memory, but due to holes in the e820 map, the main region is almost 500MB over the 32GB limit: [ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000081effffff] usable Suggestions to use 'mem=32G' to enable the L1TF mitigation while losing the 500MB revealed, that there's an off-by-one error in the check in l1tf_select_mitigation(). l1tf_pfn_limit() returns the last usable pfn (inclusive) and the range check in the mitigation path does not take this into account. Instead of amending the range check, make l1tf_pfn_limit() return the first PFN which is over the limit which is less error prone. Adjust the other users accordingly. [1] https://bugzilla.suse.com/show_bug.cgi?id=1105536 Fixes: 17dbca119312 ("x86/speculation/l1tf: Add sysfs reporting for l1tf") Reported-by: George Anchev Reported-by: Christopher Snowhill Signed-off-by: Vlastimil Babka Signed-off-by: Thomas Gleixner Cc: "H . Peter Anvin" Cc: Linus Torvalds Cc: Andi Kleen Cc: Dave Hansen Cc: Michal Hocko Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180823134418.17008-1-vbabka@suse.cz

x86/speculation/l1tf: Fix overflow in l1tf_pfn_limit() on 32bit

2018-08-20T16:04:42Z

On 32bit PAE kernels on 64bit hardware with enough physical bits, l1tf_pfn_limit() will overflow unsigned long. This in turn affects max_swapfile_size() and can lead to swapon returning -EINVAL. This has been observed in a 32bit guest with 42 bits physical address size, where max_swapfile_size() overflows exactly to 1 << 32, thus zero, and produces the following warning to dmesg: [ 6.396845] Truncating oversized swap area, only using 0k out of 2047996k Fix this by using unsigned long long instead. Fixes: 17dbca119312 ("x86/speculation/l1tf: Add sysfs reporting for l1tf") Fixes: 377eeaa8e11f ("x86/speculation/l1tf: Limit swap file size to MAX_PA/2") Reported-by: Dominique Leuenberger Reported-by: Adrian Schroeter Signed-off-by: Vlastimil Babka Signed-off-by: Thomas Gleixner Acked-by: Andi Kleen Acked-by: Michal Hocko Cc: "H . Peter Anvin" Cc: Linus Torvalds Cc: Dave Hansen Cc: Michal Hocko Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180820095835.5298-1-vbabka@suse.cz

Merge branch 'l1tf-final' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2018-08-14T16:46:06Z

Merge L1 Terminal Fault fixes from Thomas Gleixner: "L1TF, aka L1 Terminal Fault, is yet another speculative hardware engineering trainwreck. It's a hardware vulnerability which allows unprivileged speculative access to data which is available in the Level 1 Data Cache when the page table entry controlling the virtual address, which is used for the access, has the Present bit cleared or other reserved bits set. If an instruction accesses a virtual address for which the relevant page table entry (PTE) has the Present bit cleared or other reserved bits set, then speculative execution ignores the invalid PTE and loads the referenced data if it is present in the Level 1 Data Cache, as if the page referenced by the address bits in the PTE was still present and accessible. While this is a purely speculative mechanism and the instruction will raise a page fault when it is retired eventually, the pure act of loading the data and making it available to other speculative instructions opens up the opportunity for side channel attacks to unprivileged malicious code, similar to the Meltdown attack. While Meltdown breaks the user space to kernel space protection, L1TF allows to attack any physical memory address in the system and the attack works across all protection domains. It allows an attack of SGX and also works from inside virtual machines because the speculation bypasses the extended page table (EPT) protection mechanism. The assoicated CVEs are: CVE-2018-3615, CVE-2018-3620, CVE-2018-3646 The mitigations provided by this pull request include: - Host side protection by inverting the upper address bits of a non present page table entry so the entry points to uncacheable memory. - Hypervisor protection by flushing L1 Data Cache on VMENTER. - SMT (HyperThreading) control knobs, which allow to 'turn off' SMT by offlining the sibling CPU threads. The knobs are available on the kernel command line and at runtime via sysfs - Control knobs for the hypervisor mitigation, related to L1D flush and SMT control. The knobs are available on the kernel command line and at runtime via sysfs - Extensive documentation about L1TF including various degrees of mitigations. Thanks to all people who have contributed to this in various ways - patches, review, testing, backporting - and the fruitful, sometimes heated, but at the end constructive discussions. There is work in progress to provide other forms of mitigations, which might be less horrible performance wise for a particular kind of workloads, but this is not yet ready for consumption due to their complexity and limitations" * 'l1tf-final' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (75 commits) x86/microcode: Allow late microcode loading with SMT disabled tools headers: Synchronise x86 cpufeatures.h for L1TF additions x86/mm/kmmio: Make the tracer robust against L1TF x86/mm/pat: Make set_memory_np() L1TF safe x86/speculation/l1tf: Make pmd/pud_mknotpresent() invert x86/speculation/l1tf: Invert all not present mappings cpu/hotplug: Fix SMT supported evaluation KVM: VMX: Tell the nested hypervisor to skip L1D flush on vmentry x86/speculation: Use ARCH_CAPABILITIES to skip L1D flush on vmentry x86/speculation: Simplify sysfs report of VMX L1TF vulnerability Documentation/l1tf: Remove Yonah processors from not vulnerable list x86/KVM/VMX: Don't set l1tf_flush_l1d from vmx_handle_external_intr() x86/irq: Let interrupt handlers set kvm_cpu_l1tf_flush_l1d x86: Don't include linux/irq.h from asm/hardirq.h x86/KVM/VMX: Introduce per-host-cpu analogue of l1tf_flush_l1d x86/irq: Demote irq_cpustat_t::__softirq_pending to u16 x86/KVM/VMX: Move the l1tf_flush_l1d test to vmx_l1d_flush() x86/KVM/VMX: Replace 'vmx_l1d_flush_always' with 'vmx_l1d_flush_cond' x86/KVM/VMX: Don't set l1tf_flush_l1d to true from vmx_l1d_flush() cpu/hotplug: detect SMT disabled by BIOS ...