The following commit has been merged into the ras/core branch of tip: Commit-ID: 1e36d9c6886849c6f3d3c836370563e6bc1a6ddd Gitweb: https://git.kernel.org/tip/1e36d9c6886849c6f3d3c836370563e6bc1a6ddd Author: Tony Luck <tony.luck@xxxxxxxxx> AuthorDate: Mon, 24 Aug 2020 15:12:37 -07:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Wed, 26 Aug 2020 18:40:18 +02:00 x86/mce: Delay clearing IA32_MCG_STATUS to the end of do_machine_check() A long time ago, Linux cleared IA32_MCG_STATUS at the very end of machine check processing. Then, some fancy recovery and IST manipulation was added in: d4812e169de4 ("x86, mce: Get rid of TIF_MCE_NOTIFY and associated mce tricks") and clearing IA32_MCG_STATUS was pulled earlier in the function. Next change moved the actual recovery out of do_machine_check() and just used task_work_add() to schedule it later (before returning to the user): 5567d11c21a1 ("x86/mce: Send #MC singal from task work") Most recently the fancy IST footwork was removed as no longer needed: b052df3da821 ("x86/entry: Get rid of ist_begin/end_non_atomic()") At this point there is no reason remaining to clear IA32_MCG_STATUS early. It can move back to the very end of the function. Also move sync_core(). The comments for this function say that it should only be called when instructions have been changed/re-mapped. Recovery for an instruction fetch may change the physical address. But that doesn't happen until the scheduled work runs (which could be on another CPU). [ bp: Massage commit message. ] Reported-by: Gabriele Paoloni <gabriele.paoloni@xxxxxxxxx> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lkml.kernel.org/r/20200824221237.5397-1-tony.luck@xxxxxxxxx --- arch/x86/kernel/cpu/mce/core.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c index f43a78b..0ba24df 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -1190,6 +1190,7 @@ static void kill_me_maybe(struct callback_head *cb) if (!memory_failure(p->mce_addr >> PAGE_SHIFT, flags)) { set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page); + sync_core(); return; } @@ -1330,12 +1331,8 @@ noinstr void do_machine_check(struct pt_regs *regs) if (worst > 0) irq_work_queue(&mce_irq_work); - mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); - - sync_core(); - if (worst != MCE_AR_SEVERITY && !kill_it) - return; + goto out; /* Fault was in user mode and we need to take some action */ if ((m.cs & 3) == 3) { @@ -1364,6 +1361,8 @@ noinstr void do_machine_check(struct pt_regs *regs) mce_panic("Failed kernel mode recovery", &m, msg); } } +out: + mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); } EXPORT_SYMBOL_GPL(do_machine_check);
![]() |