- 08 Aug, 2018 32 commits
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Michal Hocko authored
Jan has noticed that pte_pfn and co. resp. pfn_pte are incorrect for CONFIG_PAE because phys_addr_t is wider than unsigned long and so the pte_val reps. shift left would get truncated. Fix this up by using proper types. Fixes: 6b28baca ("x86/speculation/l1tf: Protect PROT_NONE PTEs against speculation") Reported-by:
Jan Beulich <JBeulich@suse.com> Signed-off-by:
Michal Hocko <mhocko@suse.com> Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Acked-by:
Vlastimil Babka <vbabka@suse.cz> CVE-2018-3620 CVE-2018-3646 [smb: Drop change to pfn_pud which does not exist] Signed-off-by:
Stefan Bader <stefan.bader@canonical.com>
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Vlastimil Babka authored
The PAE 3-level paging code currently doesn't mitigate L1TF by flipping the offset bits, and uses the high PTE word, thus bits 32-36 for type, 37-63 for offset. The lower word is zeroed, thus systems with less than 4GB memory are safe. With 4GB to 128GB the swap type selects the memory locations vulnerable to L1TF; with even more memory, also the swap offfset influences the address. This might be a problem with 32bit PAE guests running on large 64bit hosts. By continuing to keep the whole swap entry in either high or low 32bit word of PTE we would limit the swap size too much. Thus this patch uses the whole PAE PTE with the same layout as the 64bit version does. The macros just become a bit tricky since they assume the arch-dependent swp_entry_t to be 32bit. Signed-off-by:
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Konrad Rzeszutek Wilk authored
336996-Speculative-Execution-Side-Channel-Mitigations.pdf defines a new MSR (IA32_FLUSH_CMD) which is detected by CPUID.7.EDX[28]=1 bit being set. This new MSR "gives software a way to invalidate structures with finer granularity than other architectual methods like WBINVD." A copy of this document is available at https://bugzilla.kernel.org/show_bug.cgi?id=199511Signed-off-by:
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by:
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Borislav Petkov authored
The TOPOEXT reenablement is a workaround for broken BIOSen which didn't enable the CPUID bit. amd_get_topology_early(), however, relies on that bit being set so that it can read out the CPUID leaf and set smp_num_siblings properly. Move the reenablement up to early_init_amd(). While at it, simplify amd_get_topology_early(). Signed-off-by:
Borislav Petkov <bp@suse.de> Signed-off-by:
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Vlastimil Babka authored
The previous patch has limited swap file size so that large offsets cannot clear bits above MAX_PA/2 in the pte and interfere with L1TF mitigation. It assumed that offsets are encoded starting with bit 12, same as pfn. But on x86_64, offsets are encoded starting with bit 9. Thus the limit can be raised by 3 bits. That means 16TB with 42bit MAX_PA and 256TB with 46bit MAX_PA. Fixes: 377eeaa8 ("x86/speculation/l1tf: Limit swap file size to MAX_PA/2") Signed-off-by:
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Thomas Gleixner authored
nosmt on the kernel command line merely prevents the onlining of the secondary SMT siblings. nosmt=force makes the APIC detection code ignore the secondary SMT siblings completely, so they even do not show up as possible CPUs. That reduces the amount of memory allocations for per cpu variables and saves other resources from being allocated too large. This is not fully equivalent to disabling SMT in the BIOS because the low level SMT enabling in the BIOS can result in partitioning of resources between the siblings, which is not undone by just ignoring them. Some CPUs can use the full resources when their sibling is not onlined, but this is depending on the CPU family and model and it's not well documented whether this applies to all partitioned resources. That means depending on the workload disabling SMT in the BIOS might result in better performance. Linus analysis of the Intel manual: The intel optimization manual is not very clear on what the partitioning rules are. I find: "In general, the buffers for staging instructions between major pipe stages are partitioned. These buffers include µop queues after the execution trace cache, the queues after the register rename stage, the reorder buffer which stages instructions for retirement, and the load and store buffers. In the case of load and store buffers, partitioning also provided an easier implementation to maintain memory ordering for each logical processor and detect memory ordering violations" but some of that partitioning may be relaxed if the HT thread is "not active": "In Intel microarchitecture code name Sandy Bridge, the micro-op queue is statically partitioned to provide 28 entries for each logical processor, irrespective of software executing in single thread or multiple threads. If one logical processor is not active in Intel microarchitecture code name Ivy Bridge, then a single thread executing on that processor core can use the 56 entries in the micro-op queue" but I do not know what "not active" means, and how dynamic it is. Some of that partitioning may be entirely static and depend on the early BIOS disabling of HT, and even if we park the cores, the resources will just be wasted. Signed-off-by:Ingo Molnar <mingo@kernel.org> CVE-2018-3620 CVE-2018-3646 Signed-off-by:
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Thomas Gleixner authored
To support force disabling of SMT it's required to know the number of thread siblings early. amd_get_topology() cannot be called before the APIC driver is selected, so split out the part which initializes smp_num_siblings and invoke it from amd_early_init(). Signed-off-by:
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Thomas Gleixner authored
Make use of the new early detection function to initialize smp_num_siblings on the boot cpu before the MP-Table or ACPI/MADT scan happens. That's required for force disabling SMT. Signed-off-by:
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Thomas Gleixner authored
To support force disabling of SMT it's required to know the number of thread siblings early. detect_extended_topology() cannot be called before the APIC driver is selected, so split out the part which initializes smp_num_siblings. Signed-off-by:
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Thomas Gleixner authored
To support force disabling of SMT it's required to know the number of thread siblings early. detect_ht() cannot be called before the APIC driver is selected, so split out the part which initializes smp_num_siblings. Signed-off-by:
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Thomas Gleixner authored
Real 32bit AMD CPUs do not have SMT and the only value of the call was to reach the magic printout which got removed. Signed-off-by:
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Thomas Gleixner authored
The value of this printout is dubious at best and there is no point in having it in two different places along with convoluted ways to reach it. Remove it completely. Signed-off-by:
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Suravee Suthikulpanit authored
Current implementation does not communicate whether it can successfully detect CPUID function 0xB information. Therefore, modify the function to return success or error codes. This will be used by subsequent patches. Signed-off-by:
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> Signed-off-by:
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Thomas Gleixner authored
Provide a command line and a sysfs knob to control SMT. The command line options are: 'nosmt': Enumerate secondary threads, but do not online them 'nosmt=force': Ignore secondary threads completely during enumeration via MP table and ACPI/MADT. The sysfs control file has the following states (read/write): 'on': SMT is enabled. Secondary threads can be freely onlined 'off': SMT is disabled. Secondary threads, even if enumerated cannot be onlined 'forceoff': SMT is permanentely disabled. Writes to the control file are rejected. 'notsupported': SMT is not supported by the CPU The command line option 'nosmt' sets the sysfs control to 'off'. This can be changed to 'on' to reenable SMT during runtime. The command line option 'nosmt=force' sets the sysfs control to 'forceoff'. This cannot be changed during runtime. When SMT is 'on' and the control file is changed to 'off' then all online secondary threads are offlined and attempts to online a secondary thread later on are rejected. When SMT is 'off' and the control file is changed to 'on' then secondary threads can be onlined again. The 'off' -> 'on' transition does not automatically online the secondary threads. When the control file is set to 'forceoff', the behaviour is the same as setting it to 'off', but the operation is irreversible and later writes to the control file are rejected. When the control status is 'notsupported' then writes to the control file are rejected. Signed-off-by:
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Andi Kleen authored
For SMT specific workarounds it is useful to know if SMT is active on any online CPU in the system. This currently requires a loop over all online CPUs. Add a global variable that is updated with the maximum number of smt threads on any CPU on online/offline, and use it for topology_max_smt_threads() The single call is easier to use than a loop. Not exported to user space because user space already can use the existing sibling interfaces to find this out. Signed-off-by:
Andi Kleen <ak@linux.intel.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: acme@kernel.org Cc: jolsa@kernel.org Link: http://lkml.kernel.org/r/1463703002-19686-2-git-send-email-andi@firstfloor.orgSigned-off-by:
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Thomas Gleixner authored
Split out the inner workings of do_cpu_down() to allow reuse of that function for the upcoming SMT disabling mechanism. No functional change. Signed-off-by:
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Thomas Gleixner authored
Provide information whether SMT is supoorted by the CPUs. Preparatory patch for SMT control mechanism. Suggested-by:
Dave Hansen <dave.hansen@intel.com> Signed-off-by:
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Thomas Gleixner authored
If the CPU is supporting SMT then the primary thread can be found by checking the lower APIC ID bits for zero. smp_num_siblings is used to build the mask for the APIC ID bits which need to be taken into account. This uses the MPTABLE or ACPI/MADT supplied APIC ID, which can be different than the initial APIC ID in CPUID. But according to AMD the lower bits have to be consistent. Intel gave a tentative confirmation as well. Preparatory patch to support disabling SMT at boot/runtime. Signed-off-by:
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Andi Kleen authored
For the L1TF workaround its necessary to limit the swap file size to below MAX_PA/2, so that the higher bits of the swap offset inverted never point to valid memory. Add a mechanism for the architecture to override the swap file size check in swapfile.c and add a x86 specific max swapfile check function that enforces that limit. The check is only enabled if the CPU is vulnerable to L1TF. In VMs with 42bit MAX_PA the typical limit is 2TB now, on a native system with 46bit PA it is 32TB. The limit is only per individual swap file, so it's always possible to exceed these limits with multiple swap files or partitions. Signed-off-by:
Josh Poimboeuf <jpoimboe@redhat.com> Acked-by:
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Andi Kleen authored
For L1TF PROT_NONE mappings are protected by inverting the PFN in the page table entry. This sets the high bits in the CPU's address space, thus making sure to point to not point an unmapped entry to valid cached memory. Some server system BIOSes put the MMIO mappings high up in the physical address space. If such an high mapping was mapped to unprivileged users they could attack low memory by setting such a mapping to PROT_NONE. This could happen through a special device driver which is not access protected. Normal /dev/mem is of course access protected. To avoid this forbid PROT_NONE mappings or mprotect for high MMIO mappings. Valid page mappings are allowed because the system is then unsafe anyways. It's not expected that users commonly use PROT_NONE on MMIO. But to minimize any impact this is only enforced if the mapping actually refers to a high MMIO address (defined as the MAX_PA-1 bit being set), and also skip the check for root. For mmaps this is straight forward and can be handled in vm_insert_pfn and in remap_pfn_range(). For mprotect it's a bit trickier. At the point where the actual PTEs are accessed a lot of state has been changed and it would be difficult to undo on an error. Since this is a uncommon case use a separate early page talk walk pass for MMIO PROT_NONE mappings that checks for this condition early. For non MMIO and non PROT_NONE there are no changes. Signed-off-by:
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Andi Kleen authored
L1TF core kernel workarounds are cheap and normally always enabled, However they still should be reported in sysfs if the system is vulnerable or mitigated. Add the necessary CPU feature/bug bits. - Extend the existing checks for Meltdowns to determine if the system is vulnerable. All CPUs which are not vulnerable to Meltdown are also not vulnerable to L1TF - Check for 32bit non PAE and emit a warning as there is no practical way for mitigation due to the limited physical address bits - If the system has more than MAX_PA/2 physical memory the invert page workarounds don't protect the system against the L1TF attack anymore, because an inverted physical address will also point to valid memory. Print a warning in this case and report that the system is vulnerable. Add a function which returns the PFN limit for the L1TF mitigation, which will be used in follow up patches for sanity and range checks. [ tglx: Renamed the CPU feature bit to L1TF_PTEINV ] Signed-off-by:
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Stefan Bader authored
This adds the following model numbers to intel-family.h: - INTEL_FAM6_ATOM_GEMINI_LAKE (commit 311f7770) - INTEL_FAM6_XEON_PHI_KNM (commit 0047f598) CVE-2018-3620 CVE-2018-3646 Signed-off-by:
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Andi Kleen authored
The L1TF workaround doesn't make any attempt to mitigate speculate accesses to the first physical page for zeroed PTEs. Normally it only contains some data from the early real mode BIOS. It's not entirely clear that the first page is reserved in all configurations, so add an extra reservation call to make sure it is really reserved. In most configurations (e.g. with the standard reservations) it's likely a nop. Signed-off-by:
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Andi Kleen authored
When PTEs are set to PROT_NONE the kernel just clears the Present bit and preserves the PFN, which creates attack surface for L1TF speculation speculation attacks. This is important inside guests, because L1TF speculation bypasses physical page remapping. While the host has its own migitations preventing leaking data from other VMs into the guest, this would still risk leaking the wrong page inside the current guest. This uses the same technique as Linus' swap entry patch: while an entry is is in PROTNONE state invert the complete PFN part part of it. This ensures that the the highest bit will point to non existing memory. The invert is done by pte/pmd_modify and pfn/pmd/pud_pte for PROTNONE and pte/pmd/pud_pfn undo it. This assume that no code path touches the PFN part of a PTE directly without using these primitives. This doesn't handle the case that MMIO is on the top of the CPU physical memory. If such an MMIO region was exposed by an unpriviledged driver for mmap it would be possible to attack some real memory. However this situation is all rather unlikely. For 32bit non PAE the inversion is not done because there are really not enough bits to protect anything. Q: Why does the guest need to be protected when the HyperVisor already has L1TF mitigations? A: Here's an example: Physical pages 1 2 get mapped into a guest as GPA 1 -> PA 2 GPA 2 -> PA 1 through EPT. The L1TF speculation ignores the EPT remapping. Now the guest kernel maps GPA 1 to process A and GPA 2 to process B, and they belong to different users and should be isolated. A sets the GPA 1 PA 2 PTE to PROT_NONE to bypass the EPT remapping and gets read access to the underlying physical page. Which in this case points to PA 2, so it can read process B's data, if it happened to be in L1, so isolation inside the guest is broken. There's nothing the hypervisor can do about this. This mitigation has to be done in the guest itself. [ tglx: Massaged changelog ] Signed-off-by:
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Tom Lendacky authored
Create a pgd_pfn() macro similar to the p[4um]d_pfn() macros and then use the p[g4um]d_pfn() macros in the p[g4um]d_page() macros instead of duplicating the code. Signed-off-by:
Tom Lendacky <thomas.lendacky@amd.com> Reviewed-by:
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Linus Torvalds authored
With L1 terminal fault the CPU speculates into unmapped PTEs, and resulting side effects allow to read the memory the PTE is pointing too, if its values are still in the L1 cache. For swapped out pages Linux uses unmapped PTEs and stores a swap entry into them. To protect against L1TF it must be ensured that the swap entry is not pointing to valid memory, which requires setting higher bits (between bit 36 and bit 45) that are inside the CPUs physical address space, but outside any real memory. To do this invert the offset to make sure the higher bits are always set, as long as the swap file is not too big. Note there is no workaround for 32bit !PAE, or on systems which have more than MAX_PA/2 worth of memory. The later case is very unlikely to happen on real systems. [AK: updated description and minor tweaks by. Split out from the original patch ] Signed-off-by:Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by:
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Linus Torvalds authored
If pages are swapped out, the swap entry is stored in the corresponding PTE, which has the Present bit cleared. CPUs vulnerable to L1TF speculate on PTE entries which have the present bit set and would treat the swap entry as phsyical address (PFN). To mitigate that the upper bits of the PTE must be set so the PTE points to non existent memory. The swap entry stores the type and the offset of a swapped out page in the PTE. type is stored in bit 9-13 and offset in bit 14-63. The hardware ignores the bits beyond the phsyical address space limit, so to make the mitigation effective its required to start 'offset' at the lowest possible bit so that even large swap offsets do not reach into the physical address space limit bits. Move offset to bit 9-58 and type to bit 59-63 which are the bits that hardware generally doesn't care about. That, in turn, means that if you on desktop chip with only 40 bits of physical addressing, now that the offset starts at bit 9, there needs to be 30 bits of offset actually *in use* until bit 39 ends up being set, which means when inverted it will again point into existing memory. So that's 4 terabyte of swap space (because the offset is counted in pages, so 30 bits of offset is 42 bits of actual coverage). With bigger physical addressing, that obviously grows further, until the limit of the offset is hit (at 50 bits of offset - 62 bits of actual swap file coverage). This is a preparatory change for the actual swap entry inversion to protect against L1TF. [ AK: Updated description and minor tweaks. Split into two parts ] [ tglx: Massaged changelog ] Signed-off-by:
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Andi Kleen authored
L1 Terminal Fault (L1TF) is a speculation related vulnerability. The CPU speculates on PTE entries which do not have the PRESENT bit set, if the content of the resulting physical address is available in the L1D cache. The OS side mitigation makes sure that a !PRESENT PTE entry points to a physical address outside the actually existing and cachable memory space. This is achieved by inverting the upper bits of the PTE. Due to the address space limitations this only works for 64bit and 32bit PAE kernels, but not for 32bit non PAE. This mitigation applies to both host and guest kernels, but in case of a 64bit host (hypervisor) and a 32bit PAE guest, inverting the upper bits of the PAE address space (44bit) is not enough if the host has more than 43 bits of populated memory address space, because the speculation treats the PTE content as a physical host address bypassing EPT. The host (hypervisor) protects itself against the guest by flushing L1D as needed, but pages inside the guest are not protected against attacks from other processes inside the same guest. For the guest the inverted PTE mask has to match the host to provide the full protection for all pages the host could possibly map into the guest. The hosts populated address space is not known to the guest, so the mask must cover the possible maximal host address space, i.e. 52 bit. On 32bit PAE the maximum PTE mask is currently set to 44 bit because that is the limit imposed by 32bit unsigned long PFNs in the VMs. This limits the mask to be below what the host could possible use for physical pages. The L1TF PROT_NONE protection code uses the PTE masks to determine which bits to invert to make sure the higher bits are set for unmapped entries to prevent L1TF speculation attacks against EPT inside guests. In order to invert all bits that could be used by the host, increase __PHYSICAL_PAGE_SHIFT to 52 to match 64bit. The real limit for a 32bit PAE kernel is still 44 bits because all Linux PTEs are created from unsigned long PFNs, so they cannot be higher than 44 bits on a 32bit kernel. So these extra PFN bits should be never set. The only users of this macro are using it to look at PTEs, so it's safe. [ tglx: Massaged changelog ] Signed-off-by:
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Paolo Bonzini authored
commit 3c9fa24c upstream. The functions that were used in the emulation of fxrstor, fxsave, sgdt and sidt were originally meant for task switching, and as such they did not check privilege levels. This is very bad when the same functions are used in the emulation of unprivileged instructions. This is CVE-2018-10853. The obvious fix is to add a new argument to ops->read_std and ops->write_std, which decides whether the access is a "system" access or should use the processor's CPL. Fixes: 129a72a0 ("KVM: x86: Introduce segmented_write_std", 2017-01-12) Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by:
Juerg Haefliger <juergh@canonical.com> Signed-off-by:
Khalid Elmously <khalid.elmously@canonical.com> CVE-2018-3620 CVE-2018-3646 Signed-off-by:
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Paolo Bonzini authored
commit ce14e868 upstream. Int the next patch the emulator's .read_std and .write_std callbacks will grow another argument, which is not needed in kvm_read_guest_virt and kvm_write_guest_virt_system's callers. Since we have to make separate functions, let's give the currently existing names a nicer interface, too. Fixes: 129a72a0 ("KVM: x86: Introduce segmented_write_std", 2017-01-12) Cc: stable@vger.kernel.org Signed-off-by:
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Paolo Bonzini authored
commit 79367a65 upstream. Wrap the common invocation of ctxt->ops->read_std and ctxt->ops->write_std, so as to have a smaller patch when the functions grow another argument. Fixes: 129a72a0 ("KVM: x86: Introduce segmented_write_std", 2017-01-12) Cc: stable@vger.kernel.org Signed-off-by:
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Stefan Bader authored
Ignore: yes Signed-off-by:
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- 12 Jul, 2018 4 commits
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Stefan Bader authored
Signed-off-by: -
Ross Lagerwall authored
Update the features after calling register_netdev() otherwise the device features are not set up correctly and it not possible to change the MTU of the device. After this change, the features reported by ethtool match the device's features before the commit which introduced the issue and it is possible to change the device's MTU. Fixes: f599c64f ("xen-netfront: Fix race between device setup and open") Reported-by:
Liam Shepherd <liam@dancer.es> Signed-off-by:
Ross Lagerwall <ross.lagerwall@citrix.com> Reviewed-by:
Juergen Gross <jgross@suse.com> Signed-off-by:
David S. Miller <davem@davemloft.net> BugLink: https://bugs.launchpad.net/bugs/1781413 (cherry picked from commit 45c8184c) Signed-off-by:
Colin Ian King <colin.king@canonical.com> Signed-off-by:
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Ross Lagerwall authored
Fixes: f599c64f ("xen-netfront: Fix race between device setup and open") Reported-by:
Ben Hutchings <ben.hutchings@codethink.co.uk> Signed-off-by:
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Stefan Bader authored
Ignore: yes Signed-off-by:
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- 14 Jun, 2018 4 commits
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Stefan Bader authored
Signed-off-by: -
Borislav Petkov authored
i486 derived cores like Intel Quark support only the very old, legacy x87 FPU (FSAVE/FRSTOR, CPUID bit FXSR is not set), and our FPU code wasn't handling the saving and restoring there properly in the 'eagerfpu' case. So after we made eagerfpu the default for all CPU types: 58122bf1 x86/fpu: Default eagerfpu=on on all CPUs these old FPU designs broke. First, Andy Shevchenko reported a splat: WARNING: CPU: 0 PID: 823 at arch/x86/include/asm/fpu/internal.h:163 fpu__clear+0x8c/0x160 which was us trying to execute FXRSTOR on those machines even though they don't support it. After taking care of that, Bryan O'Donoghue reported that a simple FPU test still failed because we weren't initializing the FPU state properly on those machines. Take care of all that. Reported-and-tested-by:
Bryan O'Donoghue <pure.logic@nexus-software.ie> Reported-by:
Andy Shevchenko <andy.shevchenko@gmail.com> Signed-off-by:
Tyler Hicks <tyhicks@canonical.com> Signed-off-by:
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Andy Lutomirski authored
Systems without an FPU are generally old and therefore use lazy FPU switching. Unsurprisingly, math emulation in eager FPU mode is a bit buggy. Fix it. There were two bugs involving kernel code trying to use the FPU registers in eager mode even if they didn't exist and one BUG_ON() that was incorrect. Signed-off-by:
Andy Lutomirski <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> Cc: Rik van Riel <riel@redhat.com> Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: yu-cheng yu <yu-cheng.yu@intel.com> Link: http://lkml.kernel.org/r/b4b8d112436bd6fab866e1b4011131507e8d7fbe.1453675014.git.luto@kernel.orgSigned-off-by:
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Andy Lutomirski authored
In eager fpu mode, having deactivated FPU without immediately reloading some other context is illegal. Therefore, to recover from FNSAVE, we can't just deactivate the state -- we need to reload it if we're not actively context switching. We had this wrong in fpu__save() and fpu__copy(). Fix both. __kernel_fpu_begin() was fine -- add a comment. This fixes a warning triggerable with nofxsr eagerfpu=on. Signed-off-by:
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