- 09 Aug, 2018 1 commit
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Thomas Gleixner authored
Josh reported that the late SMT evaluation in cpu_smt_state_init() sets cpu_smt_control to CPU_SMT_NOT_SUPPORTED in case that 'nosmt' was supplied on the kernel command line as it cannot differentiate between SMT disabled by BIOS and SMT soft disable via 'nosmt'. That wreckages the state and makes the sysfs interface unusable. Rework this so that during bringup of the non boot CPUs the availability of SMT is determined in cpu_smt_allowed(). If a newly booted CPU is not a 'primary' thread then set the local cpu_smt_available marker and evaluate this explicitely right after the initial SMP bringup has finished. SMT evaulation on x86 is a trainwreck as the firmware has all the information _before_ booting the kernel, but there is no interface to query it. Fixes: 73d5e2b4 ("cpu/hotplug: detect SMT disabled by BIOS") Reported-by:
Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> CVE-2018-3620 CVE-2018-3646 [smb: Context and also adjust to alternative booted_once scheme, including a move of the smt check into _cpu_up()] Signed-off-by:
Stefan Bader <stefan.bader@canonical.com>
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- 08 Aug, 2018 39 commits
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Paolo Bonzini authored
When nested virtualization is in use, VMENTER operations from the nested hypervisor into the nested guest will always be processed by the bare metal hypervisor, and KVM's "conditional cache flushes" mode in particular does a flush on nested vmentry. Therefore, include the "skip L1D flush on vmentry" bit in KVM's suggested ARCH_CAPABILITIES setting. Add the relevant Documentation. Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com> Signed-off-by:
Tyler Hicks <tyhicks@canonical.com> [smb: Minor context and adjusted documentation path] Signed-off-by:
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Paolo Bonzini authored
This lets userspace read the MSR_IA32_ARCH_CAPABILITIES and check that all requested features are available on the host. Signed-off-by:
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Wanpeng Li authored
Introduce kvm_get_msr_feature() to handle the msrs which are supported by different vendors and sharing the same emulation logic. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Liran Alon <liran.alon@oracle.com> Cc: Nadav Amit <nadav.amit@gmail.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by:
Wanpeng Li <wanpengli@tencent.com> Reviewed-by:
Radim Krčmář <rkrcmar@redhat.com> CVE-2018-3620 CVE-2018-3646 (cherry picked from commit 66421c1e) Signed-off-by:
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Tom Lendacky authored
Provide a new KVM capability that allows bits within MSRs to be recognized as features. Two new ioctls are added to the /dev/kvm ioctl routine to retrieve the list of these MSRs and then retrieve their values. A kvm_x86_ops callback is used to determine support for the listed MSR-based features. Signed-off-by:
Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by:
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KarimAllah Ahmed authored
commit 28c1c9fa Intel processors use MSR_IA32_ARCH_CAPABILITIES MSR to indicate RDCL_NO (bit 0) and IBRS_ALL (bit 1). This is a read-only MSR. By default the contents will come directly from the hardware, but user-space can still override it. [dwmw2: The bit in kvm_cpuid_7_0_edx_x86_features can be unconditional] Signed-off-by:
KarimAllah Ahmed <karahmed@amazon.de> Signed-off-by:
David Woodhouse <dwmw@amazon.co.uk> Signed-off-by:
Darren Kenny <darren.kenny@oracle.com> Reviewed-by:
Jim Mattson <jmattson@google.com> Reviewed-by:
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Jun Nakajima <jun.nakajima@intel.com> Cc: kvm@vger.kernel.org Cc: Dave Hansen <dave.hansen@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Asit Mallick <asit.k.mallick@intel.com> Cc: Arjan Van De Ven <arjan.van.de.ven@intel.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Ashok Raj <ashok.raj@intel.com> Link: https://lkml.kernel.org/r/1517522386-18410-4-git-send-email-karahmed@amazon.deSigned-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by:
Seth Forshee <seth.forshee@canonical.com> CVE-2018-3620 CVE-2018-3646 (backported from commit a6005a792e24c30cb5fa8525b91af67ca0bcc1e7 bionic) [smb: Context adjustments to work around already applied spectre patches. Also introduced specific guest_cpuid_has_arch_capabilities as replacement for non-existing guest_cpuid_has function.] Signed-off-by:
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Paolo Bonzini authored
Bit 3 of ARCH_CAPABILITIES tells a hypervisor that L1D flush on vmentry is not needed. Add a new value to enum vmx_l1d_flush_state, which is used either if there is no L1TF bug at all, or if bit 3 is set in ARCH_CAPABILITIES. Signed-off-by:
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Paolo Bonzini authored
Three changes to the content of the sysfs file: - If EPT is disabled, L1TF cannot be exploited even across threads on the same core, and SMT is irrelevant. - If mitigation is completely disabled, and SMT is enabled, print "vulnerable" instead of "vulnerable, SMT vulnerable" - Reorder the two parts so that the main vulnerability state comes first and the detail on SMT is second. Signed-off-by:
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Thomas Gleixner authored
Dave reported, that it's not confirmed that Yonah processors are unaffected. Remove them from the list. Reported-by:
ave Hansen <dave.hansen@intel.com> Signed-off-by:
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Nicolai Stange authored
For VMEXITs caused by external interrupts, vmx_handle_external_intr() indirectly calls into the interrupt handlers through the host's IDT. It follows that these interrupts get accounted for in the kvm_cpu_l1tf_flush_l1d per-cpu flag. The subsequently executed vmx_l1d_flush() will thus be aware that some interrupts have happened and conduct a L1d flush anyway. Setting l1tf_flush_l1d from vmx_handle_external_intr() isn't needed anymore. Drop it. Signed-off-by:
Nicolai Stange <nstange@suse.de> Signed-off-by:
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Nicolai Stange authored
The last missing piece to having vmx_l1d_flush() take interrupts after VMEXIT into account is to set the kvm_cpu_l1tf_flush_l1d per-cpu flag on irq entry. Issue calls to kvm_set_cpu_l1tf_flush_l1d() from entering_irq(), ipi_entering_ack_irq(), smp_reschedule_interrupt() and uv_bau_message_interrupt(). Suggested-by:
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Wanpeng Li authored
=============================== [ INFO: suspicious RCU usage. ] 4.8.0-rc6+ #5 Not tainted ------------------------------- ./arch/x86/include/asm/msr-trace.h:47 suspicious rcu_dereference_check() usage! other info that might help us debug this: RCU used illegally from idle CPU! rcu_scheduler_active = 1, debug_locks = 0 RCU used illegally from extended quiescent state! no locks held by swapper/2/0. stack backtrace: CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.8.0-rc6+ #5 Hardware name: Dell Inc. OptiPlex 7020/0F5C5X, BIOS A03 01/08/2015 0000000000000000 ffff8d1bd6003f10 ffffffff94446949 ffff8d1bd4a68000 0000000000000001 ffff8d1bd6003f40 ffffffff940e9247 ffff8d1bbdfcf3d0 000000000000080b 0000000000000000 0000000000000000 ffff8d1bd6003f70 Call Trace: <IRQ> [<ffffffff94446949>] dump_stack+0x99/0xd0 [<ffffffff940e9247>] lockdep_rcu_suspicious+0xe7/0x120 [<ffffffff9448e0d5>] do_trace_write_msr+0x135/0x140 [<ffffffff9406e750>] native_write_msr+0x20/0x30 [<ffffffff9406503d>] native_apic_msr_eoi_write+0x1d/0x30 [<ffffffff9405b17e>] smp_trace_call_function_interrupt+0x1e/0x270 [<ffffffff948cb1d6>] trace_call_function_interrupt+0x96/0xa0 <EOI> [<ffffffff947200f4>] ? cpuidle_enter_state+0xe4/0x360 [<ffffffff947200df>] ? cpuidle_enter_state+0xcf/0x360 [<ffffffff947203a7>] cpuidle_enter+0x17/0x20 [<ffffffff940df008>] cpu_startup_entry+0x338/0x4d0 [<ffffffff9405bfc4>] start_secondary+0x154/0x180 This can be reproduced readily by running ftrace test case of kselftest. Move the irq_enter() call before ack_APIC_irq(), because irq_enter() tells the RCU susbstems to end the extended quiescent state, so that the following trace call in ack_APIC_irq() works correctly. The same applies to exiting_ack_irq() which calls ack_APIC_irq() after irq_exit(). [ tglx: Massaged changelog ] Signed-off-by:
Wanpeng Li <wanpeng.li@hotmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Wanpeng Li <wanpeng.li@hotmail.com> Link: http://lkml.kernel.org/r/1474198491-3738-1-git-send-email-wanpeng.li@hotmail.comSigned-off-by:
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Nicolai Stange authored
The next patch in this series will have to make the definition of irq_cpustat_t available to entering_irq(). Inclusion of asm/hardirq.h into asm/apic.h would cause circular header dependencies like asm/smp.h asm/apic.h asm/hardirq.h linux/irq.h linux/topology.h linux/smp.h asm/smp.h or linux/gfp.h linux/mmzone.h asm/mmzone.h asm/mmzone_64.h asm/smp.h asm/apic.h asm/hardirq.h linux/irq.h linux/irqdesc.h linux/kobject.h linux/sysfs.h linux/kernfs.h linux/idr.h linux/gfp.h and others. This causes compilation errors because of the header guards becoming effective in the second inclusion: symbols/macros that had been defined before wouldn't be available to intermediate headers in the #include chain anymore. A possible workaround would be to move the definition of irq_cpustat_t into its own header and include that from both, asm/hardirq.h and asm/apic.h. However, this wouldn't solve the real problem, namely asm/harirq.h unnecessarily pulling in all the linux/irq.h cruft: nothing in asm/hardirq.h itself requires it. Also, note that there are some other archs, like e.g. arm64, which don't have that #include in their asm/hardirq.h. Remove the linux/irq.h #include from x86' asm/hardirq.h. Fix resulting compilation errors by adding appropriate #includes to *.c files as needed. Note that some of these *.c files could be cleaned up a bit wrt. to their set of #includes, but that should better be done from separate patches, if at all. Signed-off-by: -
Nicolai Stange authored
Part of the L1TF mitigation for vmx includes flushing the L1D cache upon VMENTRY. L1D flushes are costly and two modes of operations are provided to users: "always" and the more selective "conditional" mode. If operating in the latter, the cache would get flushed only if a host side code path considered unconfined had been traversed. "Unconfined" in this context means that it might have pulled in sensitive data like user data or kernel crypto keys. The need for L1D flushes is tracked by means of the per-vcpu flag l1tf_flush_l1d. KVM exit handlers considered unconfined set it. A vmx_l1d_flush() subsequently invoked before the next VMENTER will conduct a L1d flush based on its value and reset that flag again. Currently, interrupts delivered "normally" while in root operation between VMEXIT and VMENTER are not taken into account. Part of the reason is that these don't leave any traces and thus, the vmx code is unable to tell if any such has happened. As proposed by Paolo Bonzini, prepare for tracking all interrupts by introducing a new per-cpu flag, "kvm_cpu_l1tf_flush_l1d". It will be in strong analogy to the per-vcpu ->l1tf_flush_l1d. A later patch will make interrupt handlers set it. For the sake of cache locality, group kvm_cpu_l1tf_flush_l1d into x86' per-cpu irq_cpustat_t as suggested by Peter Zijlstra. Provide the helpers kvm_set_cpu_l1tf_flush_l1d(), kvm_clear_cpu_l1tf_flush_l1d() and kvm_get_cpu_l1tf_flush_l1d(). Make them trivial resp. non-existent for !CONFIG_KVM_INTEL as appropriate. Let vmx_l1d_flush() handle kvm_cpu_l1tf_flush_l1d in the same way as l1tf_flush_l1d. Suggested-by:
Peter Zijlstra <peterz@infradead.org> Signed-off-by:
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Nicolai Stange authored
An upcoming patch will extend KVM's L1TF mitigation in conditional mode to also cover interrupts after VMEXITs. For tracking those, stores to a new per-cpu flag from interrupt handlers will become necessary. In order to improve cache locality, this new flag will be added to x86's irq_cpustat_t. Make some space available there by shrinking the ->softirq_pending bitfield from 32 to 16 bits: the number of bits actually used is only NR_SOFTIRQS, i.e. 10. Suggested-by:
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Nicolai Stange authored
Currently, vmx_vcpu_run() checks if l1tf_flush_l1d is set and invokes vmx_l1d_flush() if so. This test is unncessary for the "always flush L1D" mode. Move the check to vmx_l1d_flush()'s conditional mode code path. Notes: - vmx_l1d_flush() is likely to get inlined anyway and thus, there's no extra function call. - This inverts the (static) branch prediction, but there hadn't been any explicit likely()/unlikely() annotations before and so it stays as is. Signed-off-by:
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Nicolai Stange authored
The vmx_l1d_flush_always static key is only ever evaluated if vmx_l1d_should_flush is enabled. In that case however, there are only two L1d flushing modes possible: "always" and "conditional". The "conditional" mode's implementation tends to require more sophisticated logic than the "always" mode. Avoid inverted logic by replacing the 'vmx_l1d_flush_always' static key with a 'vmx_l1d_flush_cond' one. There is no change in functionality. Signed-off-by:
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Nicolai Stange authored
vmx_l1d_flush() gets invoked only if l1tf_flush_l1d is true. There's no point in setting l1tf_flush_l1d to true from there again. Signed-off-by:
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Josh Poimboeuf authored
If SMT is disabled in BIOS, the CPU code doesn't properly detect it. The /sys/devices/system/cpu/smt/control file shows 'on', and the 'l1tf' vulnerabilities file shows SMT as vulnerable. Fix it by forcing 'cpu_smt_control' to CPU_SMT_NOT_SUPPORTED in such a case. Unfortunately the detection can only be done after bringing all the CPUs online, so we have to overwrite any previous writes to the variable. Reported-by:
Joe Mario <jmario@redhat.com> Tested-by:
Jiri Kosina <jkosina@suse.cz> Fixes: f048c399 ("x86/topology: Provide topology_smt_supported()") Signed-off-by:
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Tony Luck authored
Fix spelling and other typos Signed-off-by:
Tony Luck <tony.luck@intel.com> Signed-off-by:
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Nicolai Stange authored
The slow path in vmx_l1d_flush() reads from vmx_l1d_flush_pages in order to evict the L1d cache. However, these pages are never cleared and, in theory, their data could be leaked. More importantly, KSM could merge a nested hypervisor's vmx_l1d_flush_pages to fewer than 1 << L1D_CACHE_ORDER host physical pages and this would break the L1d flushing algorithm: L1D on x86_64 is tagged by physical addresses. Fix this by initializing the individual vmx_l1d_flush_pages with a different pattern each. Rename the "empty_zp" asm constraint identifier in vmx_l1d_flush() to "flush_pages" to reflect this change. Fixes: a47dd5f0 ("x86/KVM/VMX: Add L1D flush algorithm") Signed-off-by:
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Jiri Kosina authored
pfn_modify_allowed() and arch_has_pfn_modify_check() are outside of the !__ASSEMBLY__ section in include/asm-generic/pgtable.h, which confuses assembler on archs that don't have __HAVE_ARCH_PFN_MODIFY_ALLOWED (e.g. ia64) and breaks build: include/asm-generic/pgtable.h: Assembler messages: include/asm-generic/pgtable.h:538: Error: Unknown opcode `static inline bool pfn_modify_allowed(unsigned long pfn,pgprot_t prot)' include/asm-generic/pgtable.h:540: Error: Unknown opcode `return true' include/asm-generic/pgtable.h:543: Error: Unknown opcode `static inline bool arch_has_pfn_modify_check(void)' include/asm-generic/pgtable.h:545: Error: Unknown opcode `return false' arch/ia64/kernel/entry.S:69: Error: `mov' does not fit into bundle Move those two static inlines into the !__ASSEMBLY__ section so that they don't confuse the asm build pass. Fixes: 42e4089c ("x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings") Signed-off-by: -
Thomas Gleixner authored
Add documentation for the L1TF vulnerability and the mitigation mechanisms: - Explain the problem and risks - Document the mitigation mechanisms - Document the command line controls - Document the sysfs files Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org> Link: https://lkml.kernel.org/r/20180713142323.287429944@linutronix.de CVE-2018-3620 CVE-2018-3646 [smb: Added document as Documentation/security/l1tf.txt instead.] Signed-off-by:
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Jiri Kosina authored
Introduce the 'l1tf=' kernel command line option to allow for boot-time switching of mitigation that is used on processors affected by L1TF. The possible values are: full Provides all available mitigations for the L1TF vulnerability. Disables SMT and enables all mitigations in the hypervisors. SMT control via /sys/devices/system/cpu/smt/control is still possible after boot. Hypervisors will issue a warning when the first VM is started in a potentially insecure configuration, i.e. SMT enabled or L1D flush disabled. full,force Same as 'full', but disables SMT control. Implies the 'nosmt=force' command line option. sysfs control of SMT and the hypervisor flush control is disabled. flush Leaves SMT enabled and enables the conditional hypervisor mitigation. Hypervisors will issue a warning when the first VM is started in a potentially insecure configuration, i.e. SMT enabled or L1D flush disabled. flush,nosmt Disables SMT and enables the conditional hypervisor mitigation. SMT control via /sys/devices/system/cpu/smt/control is still possible after boot. If SMT is reenabled or flushing disabled at runtime hypervisors will issue a warning. flush,nowarn Same as 'flush', but hypervisors will not warn when a VM is started in a potentially insecure configuration. off Disables hypervisor mitigations and doesn't emit any warnings. Default is 'flush'. Let KVM adhere to these semantics, which means: - 'lt1f=full,force' : Performe L1D flushes. No runtime control possible. - 'l1tf=full' - 'l1tf-flush' - 'l1tf=flush,nosmt' : Perform L1D flushes and warn on VM start if SMT has been runtime enabled or L1D flushing has been run-time enabled - 'l1tf=flush,nowarn' : Perform L1D flushes and no warnings are emitted. - 'l1tf=off' : L1D flushes are not performed and no warnings are emitted. KVM can always override the L1D flushing behavior using its 'vmentry_l1d_flush' module parameter except when lt1f=full,force is set. This makes KVM's private 'nosmt' option redundant, and as it is a bit non-systematic anyway (this is something to control globally, not on hypervisor level), remove that option. Add the missing Documentation entry for the l1tf vulnerability sysfs file while at it. Signed-off-by: -
Thomas Gleixner authored
The CPU_SMT_NOT_SUPPORTED state is set (if the processor does not support SMT) when the sysfs SMT control file is initialized. That was fine so far as this was only required to make the output of the control file correct and to prevent writes in that case. With the upcoming l1tf command line parameter, this needs to be set up before the L1TF mitigation selection and command line parsing happens. Signed-off-by:
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Jiri Kosina authored
The L1TF mitigation will gain a commend line parameter which allows to set a combination of hypervisor mitigation and SMT control. Expose cpu_smt_disable() so the command line parser can tweak SMT settings. [ tglx: Split out of larger patch and made it preserve an already existing force off state ] Signed-off-by:
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Thomas Gleixner authored
All mitigation modes can be switched at run time with a static key now: - Use sysfs_streq() instead of strcmp() to handle the trailing new line from sysfs writes correctly. - Make the static key management handle multiple invocations properly. - Set the module parameter file to RW Signed-off-by:
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Thomas Gleixner authored
Writes to the parameter files are not serialized at the sysfs core level, so local serialization is required. Signed-off-by:
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Thomas Gleixner authored
Avoid the conditional in the L1D flush control path. Signed-off-by:
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Thomas Gleixner authored
In preparation of allowing run time control for L1D flushing, move the setup code to the module parameter handler. In case of pre module init parsing, just store the value and let vmx_init() do the actual setup after running kvm_init() so that enable_ept is having the correct state. During run-time invoke it directly from the parameter setter to prepare for run-time control. Signed-off-by:
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Thomas Gleixner authored
If Extended Page Tables (EPT) are disabled or not supported, no L1D flushing is required. The setup function can just avoid setting up the L1D flush for the EPT=n case. Invoke it after the hardware setup has be done and enable_ept has the correct state and expose the EPT disabled state in the mitigation status as well. Signed-off-by:
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Thomas Gleixner authored
The VMX module parameter to control the L1D flush should become writeable. The MSR list is set up at VM init per guest VCPU, but the run time switching is based on a static key which is global. Toggling the MSR list at run time might be feasible, but for now drop this optimization and use the regular MSR write to make run-time switching possible. The default mitigation is the conditional flush anyway, so for extra paranoid setups this will add some small overhead, but the extra code executed is in the noise compared to the flush itself. Aside of that the EPT disabled case is not handled correctly at the moment and the MSR list magic is in the way for fixing that as well. If it's really providing a significant advantage, then this needs to be revisited after the code is correct and the control is writable. Signed-off-by:
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Thomas Gleixner authored
Store the effective mitigation of VMX in a status variable and use it to report the VMX state in the l1tf sysfs file. Signed-off-by:
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Thomas Gleixner authored
Writing 'off' to /sys/devices/system/cpu/smt/control offlines all SMT siblings. Writing 'on' merily enables the abilify to online them, but does not online them automatically. Make 'on' more useful by onlining all offline siblings. Signed-off-by:
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Konrad Rzeszutek Wilk authored
If the L1D flush module parameter is set to 'always' and the IA32_FLUSH_CMD MSR is available, optimize the VMENTER code with the MSR save list. Signed-off-by:
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Konrad Rzeszutek Wilk authored
The IA32_FLUSH_CMD MSR needs only to be written on VMENTER. Extend add_atomic_switch_msr() with an entry_only parameter to allow storing the MSR only in the guest (ENTRY) MSR array. Signed-off-by:
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Konrad Rzeszutek Wilk authored
This allows to load a different number of MSRs depending on the context: VMEXIT or VMENTER. Signed-off-by:
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Konrad Rzeszutek Wilk authored
.. to help find the MSR on either the guest or host MSR list. Signed-off-by:
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Konrad Rzeszutek Wilk authored
There is no semantic change but this change allows an unbalanced amount of MSRs to be loaded on VMEXIT and VMENTER, i.e. the number of MSRs to save or restore on VMEXIT or VMENTER may be different. That is the number of MSRs to save or restore on VMEXIT or VMENTER may be different. Signed-off-by:
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Paolo Bonzini authored
Add the logic for flushing L1D on VMENTER. The flush depends on the static key being enabled and the new l1tf_flush_l1d flag being set. The flags is set: - Always, if the flush module parameter is 'always' - Conditionally at: - Entry to vcpu_run(), i.e. after executing user space - From the sched_in notifier, i.e. when switching to a vCPU thread. - From vmexit handlers which are considered unsafe, i.e. where sensitive data can be brought into L1D: - The emulator, which could be a good target for other speculative execution-based threats, - The MMU, which can bring host page tables in the L1 cache. - External interrupts - Nested operations that require the MMU (see above). That is vmptrld, vmptrst, vmclear,vmwrite,vmread. - When handling invept,invvpid [ tglx: Split out from combo patch and reduced to a single flag ] Signed-off-by:
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