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    Subject[PATCH 4.16 078/272] x86/mm: Fix bogus warning during EFI bootup, use boot_cpu_has() instead of this_cpu_has() in build_cr3_noflush()
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Sai Praneeth <sai.praneeth.prakhya@intel.com>

    [ Upstream commit 162ee5a8ab49be40d253f90e94aef712470a3a24 ]

    Linus reported the following boot warning:

    WARNING: CPU: 0 PID: 0 at arch/x86/include/asm/tlbflush.h:134 load_new_mm_cr3+0x114/0x170
    [...]
    Call Trace:
    switch_mm_irqs_off+0x267/0x590
    switch_mm+0xe/0x20
    efi_switch_mm+0x3e/0x50
    efi_enter_virtual_mode+0x43f/0x4da
    start_kernel+0x3bf/0x458
    secondary_startup_64+0xa5/0xb0

    ... after merging:

    03781e40890c: x86/efi: Use efi_switch_mm() rather than manually twiddling with %cr3

    When the platform supports PCID and if CONFIG_DEBUG_VM=y is enabled,
    build_cr3_noflush() (called via switch_mm()) does a sanity check to see
    if X86_FEATURE_PCID is set.

    Presently, build_cr3_noflush() uses "this_cpu_has(X86_FEATURE_PCID)" to
    perform the check but this_cpu_has() works only after SMP is initialized
    (i.e. per cpu cpu_info's should be populated) and this happens to be very
    late in the boot process (during rest_init()).

    As efi_runtime_services() are called during (early) kernel boot time
    and run time, modify build_cr3_noflush() to use boot_cpu_has() all the
    time. As suggested by Dave Hansen, this should be OK because all CPU's have
    same capabilities on x86.

    With this change the warning is fixed.

    ( Dave also suggested that we put a warning in this_cpu_has() if it's used
    early in the boot process. This is still work in progress as it affects
    MCE. )

    Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Lee Chun-Yi <jlee@suse.com>
    Cc: Matt Fleming <matt@codeblueprint.co.uk>
    Cc: Michael S. Tsirkin <mst@redhat.com>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ravi Shankar <ravi.v.shankar@intel.com>
    Cc: Ricardo Neri <ricardo.neri@intel.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: linux-efi@vger.kernel.org
    Link: http://lkml.kernel.org/r/1522870459-7432-1-git-send-email-sai.praneeth.prakhya@intel.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/include/asm/tlbflush.h | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    --- a/arch/x86/include/asm/tlbflush.h
    +++ b/arch/x86/include/asm/tlbflush.h
    @@ -131,7 +131,12 @@ static inline unsigned long build_cr3(pg
    static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
    {
    VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
    - VM_WARN_ON_ONCE(!this_cpu_has(X86_FEATURE_PCID));
    + /*
    + * Use boot_cpu_has() instead of this_cpu_has() as this function
    + * might be called during early boot. This should work even after
    + * boot because all CPU's the have same capabilities:
    + */
    + VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
    return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
    }


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