https://github.com/torvalds/linux
Revision b357ddfaa5e252108a22b31ea2b584bcc48aad5a authored by Tim Chen on 29 January 2018, 22:04:47 UTC, committed by Seth Forshee on 08 February 2018, 03:08:35 UTC
BugLink: http://bugs.launchpad.net/bugs/1748072 commit 18bf3c3ea8ece8f03b6fc58508f2dfd23c7711c7 Flush indirect branches when switching into a process that marked itself non dumpable. This protects high value processes like gpg better, without having too high performance overhead. If done naïvely, we could switch to a kernel idle thread and then back to the original process, such as: process A -> idle -> process A In such scenario, we do not have to do IBPB here even though the process is non-dumpable, as we are switching back to the same process after a hiatus. To avoid the redundant IBPB, which is expensive, we track the last mm user context ID. The cost is to have an extra u64 mm context id to track the last mm we were using before switching to the init_mm used by idle. Avoiding the extra IBPB is probably worth the extra memory for this common scenario. For those cases where tlb_defer_switch_to_init_mm() returns true (non PCID), lazy tlb will defer switch to init_mm, so we will not be changing the mm for the process A -> idle -> process A switch. So IBPB will be skipped for this case. Thanks to the reviewers and Andy Lutomirski for the suggestion of using ctx_id which got rid of the problem of mm pointer recycling. Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: ak@linux.intel.com Cc: karahmed@amazon.de Cc: arjan@linux.intel.com Cc: torvalds@linux-foundation.org Cc: linux@dominikbrodowski.net Cc: peterz@infradead.org Cc: bp@alien8.de Cc: luto@kernel.org Cc: pbonzini@redhat.com Cc: gregkh@linux-foundation.org Link: https://lkml.kernel.org/r/1517263487-3708-1-git-send-email-dwmw@amazon.co.uk Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
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Tip revision: b357ddfaa5e252108a22b31ea2b584bcc48aad5a authored by Tim Chen on 29 January 2018, 22:04:47 UTC
x86/speculation: Use Indirect Branch Prediction Barrier in context switch
x86/speculation: Use Indirect Branch Prediction Barrier in context switch
Tip revision: b357ddf
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Makefile | -rw-r--r-- | 59.3 KB |
README | -rw-r--r-- | 722 bytes |
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snapcraft.yaml | -rw-r--r-- | 607 bytes |
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