kernel/git/stable/linux.git/arch/x86/lib, branch linux-5.8.y

x86/copy_mc: Introduce copy_mc_enhanced_fast_string()

2020-11-01T11:45:37+00:00

commit 5da8e4a658109e3b7e1f45ae672b7c06ac3e7158 upstream. The motivations to go rework memcpy_mcsafe() are that the benefit of doing slow and careful copies is obviated on newer CPUs, and that the current opt-in list of CPUs to instrument recovery is broken relative to those CPUs. There is no need to keep an opt-in list up to date on an ongoing basis if pmem/dax operations are instrumented for recovery by default. With recovery enabled by default the old "mcsafe_key" opt-in to careful copying can be made a "fragile" opt-out. Where the "fragile" list takes steps to not consume poison across cachelines. The discussion with Linus made clear that the current "_mcsafe" suffix was imprecise to a fault. The operations that are needed by pmem/dax are to copy from a source address that might throw #MC to a destination that may write-fault, if it is a user page. So copy_to_user_mcsafe() becomes copy_mc_to_user() to indicate the separate precautions taken on source and destination. copy_mc_to_kernel() is introduced as a non-SMAP version that does not expect write-faults on the destination, but is still prepared to abort with an error code upon taking #MC. The original copy_mc_fragile() implementation had negative performance implications since it did not use the fast-string instruction sequence to perform copies. For this reason copy_mc_to_kernel() fell back to plain memcpy() to preserve performance on platforms that did not indicate the capability to recover from machine check exceptions. However, that capability detection was not architectural and now that some platforms can recover from fast-string consumption of memory errors the memcpy() fallback now causes these more capable platforms to fail. Introduce copy_mc_enhanced_fast_string() as the fast default implementation of copy_mc_to_kernel() and finalize the transition of copy_mc_fragile() to be a platform quirk to indicate 'copy-carefully'. With this in place, copy_mc_to_kernel() is fast and recovery-ready by default regardless of hardware capability. Thanks to Vivek for identifying that copy_user_generic() is not suitable as the copy_mc_to_user() backend since the #MC handler explicitly checks ex_has_fault_handler(). Thanks to the 0day robot for catching a performance bug in the x86/copy_mc_to_user implementation. [ bp: Add the "why" for this change from the 0/2th message, massage. ] Fixes: 92b0729c34ca ("x86/mm, x86/mce: Add memcpy_mcsafe()") Reported-by: Erwin Tsaur Reported-by: 0day robot Signed-off-by: Dan Williams Signed-off-by: Borislav Petkov Reviewed-by: Tony Luck Tested-by: Erwin Tsaur Cc: Link: https://lkml.kernel.org/r/160195562556.2163339.18063423034951948973.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Greg Kroah-Hartman

x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}()

2020-11-01T11:45:37+00:00

commit ec6347bb43395cb92126788a1a5b25302543f815 upstream. In reaction to a proposal to introduce a memcpy_mcsafe_fast() implementation Linus points out that memcpy_mcsafe() is poorly named relative to communicating the scope of the interface. Specifically what addresses are valid to pass as source, destination, and what faults / exceptions are handled. Of particular concern is that even though x86 might be able to handle the semantics of copy_mc_to_user() with its common copy_user_generic() implementation other archs likely need / want an explicit path for this case: On Fri, May 1, 2020 at 11:28 AM Linus Torvalds wrote: > > On Thu, Apr 30, 2020 at 6:21 PM Dan Williams wrote: > > > > However now I see that copy_user_generic() works for the wrong reason. > > It works because the exception on the source address due to poison > > looks no different than a write fault on the user address to the > > caller, it's still just a short copy. So it makes copy_to_user() work > > for the wrong reason relative to the name. > > Right. > > And it won't work that way on other architectures. On x86, we have a > generic function that can take faults on either side, and we use it > for both cases (and for the "in_user" case too), but that's an > artifact of the architecture oddity. > > In fact, it's probably wrong even on x86 - because it can hide bugs - > but writing those things is painful enough that everybody prefers > having just one function. Replace a single top-level memcpy_mcsafe() with either copy_mc_to_user(), or copy_mc_to_kernel(). Introduce an x86 copy_mc_fragile() name as the rename for the low-level x86 implementation formerly named memcpy_mcsafe(). It is used as the slow / careful backend that is supplanted by a fast copy_mc_generic() in a follow-on patch. One side-effect of this reorganization is that separating copy_mc_64.S to its own file means that perf no longer needs to track dependencies for its memcpy_64.S benchmarks. [ bp: Massage a bit. ] Signed-off-by: Dan Williams Signed-off-by: Borislav Petkov Reviewed-by: Tony Luck Acked-by: Michael Ellerman Cc: Link: http://lore.kernel.org/r/CAHk-=wjSqtXAqfUJxFtWNwmguFASTgB0dz1dT3V-78Quiezqbg@mail.gmail.com Link: https://lkml.kernel.org/r/160195561680.2163339.11574962055305783722.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Greg Kroah-Hartman

arch/x86/lib/usercopy_64.c: fix __copy_user_flushcache() cache writeback

2020-10-01T15:36:32+00:00

commit a1cd6c2ae47ee10ff21e62475685d5b399e2ed4a upstream. If we copy less than 8 bytes and if the destination crosses a cache line, __copy_user_flushcache would invalidate only the first cache line. This patch makes it invalidate the second cache line as well. Fixes: 0aed55af88345b ("x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations") Signed-off-by: Mikulas Patocka Signed-off-by: Andrew Morton Reviewed-by: Dan Williams Cc: Jan Kara Cc: Jeff Moyer Cc: Ingo Molnar Cc: Christoph Hellwig Cc: Toshi Kani Cc: "H. Peter Anvin" Cc: Al Viro Cc: Thomas Gleixner Cc: Matthew Wilcox Cc: Ross Zwisler Cc: Ingo Molnar Cc: Link: https://lkml.kernel.org/r/alpine.LRH.2.02.2009161451140.21915@file01.intranet.prod.int.rdu2.redhat.com Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

Merge tag 'x86_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-06-28T17:35:01+00:00

Pull x86 fixes from Borislav Petkov: - AMD Memory bandwidth counter width fix, by Babu Moger. - Use the proper length type in the 32-bit truncate() syscall variant, by Jiri Slaby. - Reinit IA32_FEAT_CTL during wakeup to fix the case where after resume, VMXON would #GP due to VMX not being properly enabled, by Sean Christopherson. - Fix a static checker warning in the resctrl code, by Dan Carpenter. - Add a CR4 pinning mask for bits which cannot change after boot, by Kees Cook. - Align the start of the loop of __clear_user() to 16 bytes, to improve performance on AMD zen1 and zen2 microarchitectures, by Matt Fleming. * tag 'x86_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/asm/64: Align start of __clear_user() loop to 16-bytes x86/cpu: Use pinning mask for CR4 bits needing to be 0 x86/resctrl: Fix a NULL vs IS_ERR() static checker warning in rdt_cdp_peer_get() x86/cpu: Reinitialize IA32_FEAT_CTL MSR on BSP during wakeup syscalls: Fix offset type of ksys_ftruncate() x86/resctrl: Fix memory bandwidth counter width for AMD

x86/entry: Fixup bad_iret vs noinstr

2020-06-25T11:45:39+00:00

vmlinux.o: warning: objtool: fixup_bad_iret()+0x8e: call to memcpy() leaves .noinstr.text section Worse, when KASAN there is no telling what memcpy() actually is. Force the use of __memcpy() which is our assmebly implementation. Reported-by: Marco Elver Suggested-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Tested-by: Marco Elver Link: https://lkml.kernel.org/r/20200618144801.760070502@infradead.org

x86/asm/64: Align start of __clear_user() loop to 16-bytes

2020-06-19T16:32:11+00:00

x86 CPUs can suffer severe performance drops if a tight loop, such as the ones in __clear_user(), straddles a 16-byte instruction fetch window, or worse, a 64-byte cacheline. This issues was discovered in the SUSE kernel with the following commit, 1153933703d9 ("x86/asm/64: Micro-optimize __clear_user() - Use immediate constants") which increased the code object size from 10 bytes to 15 bytes and caused the 8-byte copy loop in __clear_user() to be split across a 64-byte cacheline. Aligning the start of the loop to 16-bytes makes this fit neatly inside a single instruction fetch window again and restores the performance of __clear_user() which is used heavily when reading from /dev/zero. Here are some numbers from running libmicro's read_z* and pread_z* microbenchmarks which read from /dev/zero: Zen 1 (Naples) libmicro-file 5.7.0-rc6 5.7.0-rc6 5.7.0-rc6 revert-1153933703d9+ align16+ Time mean95-pread_z100k 9.9195 ( 0.00%) 5.9856 ( 39.66%) 5.9938 ( 39.58%) Time mean95-pread_z10k 1.1378 ( 0.00%) 0.7450 ( 34.52%) 0.7467 ( 34.38%) Time mean95-pread_z1k 0.2623 ( 0.00%) 0.2251 ( 14.18%) 0.2252 ( 14.15%) Time mean95-pread_zw100k 9.9974 ( 0.00%) 6.0648 ( 39.34%) 6.0756 ( 39.23%) Time mean95-read_z100k 9.8940 ( 0.00%) 5.9885 ( 39.47%) 5.9994 ( 39.36%) Time mean95-read_z10k 1.1394 ( 0.00%) 0.7483 ( 34.33%) 0.7482 ( 34.33%) Note that this doesn't affect Haswell or Broadwell microarchitectures which seem to avoid the alignment issue by executing the loop straight out of the Loop Stream Detector (verified using perf events). Fixes: 1153933703d9 ("x86/asm/64: Micro-optimize __clear_user() - Use immediate constants") Signed-off-by: Matt Fleming Signed-off-by: Borislav Petkov Cc: # v4.19+ Link: https://lkml.kernel.org/r/20200618102002.30034-1-matt@codeblueprint.co.uk

Rebase locking/kcsan to locking/urgent

2020-06-11T18:02:46+00:00

Merge the state of the locking kcsan branch before the read/write_once() and the atomics modifications got merged. Squash the fallout of the rebase on top of the read/write once and atomic fallback work into the merge. The history of the original branch is preserved in tag locking-kcsan-2020-06-02. Signed-off-by: Thomas Gleixner

Merge tag 'x86-timers-2020-06-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-06-03T17:18:09+00:00

Pull x86 timer updates from Thomas Gleixner: "X86 timer specific updates: - Add TPAUSE based delay which allows the CPU to enter an optimized power state while waiting for the delay to pass. The delay is based on TSC cycles. - Add tsc_early_khz command line parameter to workaround the problem that overclocked CPUs can report the wrong frequency via CPUID.16h which causes the refined calibration to fail because the delta to the initial frequency value is too big. With the parameter users can provide an halfways accurate initial value" * tag 'x86-timers-2020-06-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/tsc: Add tsc_early_khz command line parameter x86/delay: Introduce TPAUSE delay x86/delay: Refactor delay_mwaitx() for TPAUSE support x86/delay: Preparatory code cleanup

Merge branch 'uaccess.csum' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2020-06-01T23:03:37+00:00

Pull uaccess/csum updates from Al Viro: "Regularize the sitation with uaccess checksum primitives: - fold csum_partial_... into csum_and_copy_..._user() - on x86 collapse several access_ok()/stac()/clac() into user_access_begin()/user_access_end()" * 'uaccess.csum' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: default csum_and_copy_to_user(): don't bother with access_ok() take the dummy csum_and_copy_from_user() into net/checksum.h arm: switch to csum_and_copy_from_user() sh32: convert to csum_and_copy_from_user() m68k: convert to csum_and_copy_from_user() xtensa: switch to providing csum_and_copy_from_user() sparc: switch to providing csum_and_copy_from_user() parisc: turn csum_partial_copy_from_user() into csum_and_copy_from_user() alpha: turn csum_partial_copy_from_user() into csum_and_copy_from_user() ia64: turn csum_partial_copy_from_user() into csum_and_copy_from_user() ia64: csum_partial_copy_nocheck(): don't abuse csum_partial_copy_from_user() x86: switch 32bit csum_and_copy_to_user() to user_access_{begin,end}() x86: switch both 32bit and 64bit to providing csum_and_copy_from_user() x86_64: csum_..._copy_..._user(): switch to unsafe_..._user() get rid of csum_partial_copy_to_user()

x86: switch both 32bit and 64bit to providing csum_and_copy_from_user()

2020-05-29T20:11:48+00:00

... rather than messing with the wrapper. As a side effect, 32bit variant gets access_ok() into it and can be switched to user_access_begin()/user_access_end() Signed-off-by: Al Viro