Messages in this thread | | | Subject | Re: [PATCH v7 6/6] x86/split_lock: Fix the split lock #AC handling when running as guest | From | Sathyanarayanan Kuppuswamy <> | Date | Wed, 13 Oct 2021 19:21:26 -0700 |
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On 10/13/21 6:24 PM, Xiaoyao Li wrote: > On 10/14/2021 5:32 AM, Sathyanarayanan Kuppuswamy wrote: >> + Xiaoyao >> >> On 10/13/21 1:30 PM, Sean Christopherson wrote: >>> On Tue, Oct 05, 2021, Kuppuswamy Sathyanarayanan wrote: >>>> From: Xiaoyao Li <xiaoyao.li@intel.com> >>>> >>>> If running as guest and hypervisor enables >>>> MSR_TEST_CTRL.SPLIT_LOCK_DETECT during its running, it can get split >>>> lock #AC even though sld_state is sld_off. >>> That's a hypervisor bug, no? The hypervisor should never inject a >>> fault that >>> the guest cannot reasonably expect. > > What if hypervisor doesn't intercept #AC and host enables > SPLIT_LOCK_DETECT during guest running? That's exactly the case TDX is > facing. > > (BTW, this patch is not complete that no matter what state sld_state > is, it should always treat it as fatal even sld_warn because sld_warn > doesn't guarantee SPLIT_LOCK_DETECT is available) > > Sathya, we need to drop this one. Andi has anther one to disable split > lock detection for SPR. That's a better direction.
Ok. I will fix this in next submission.
> >>>> For kernel mode #AC, it always dies("split lock"), no more action >>>> needed. >>>> >>>> For user mode #AC, it should treat sld_off (default state when feature >>>> is not available) as fatal as well. >>>> >>>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> >>>> Signed-off-by: Kuppuswamy Sathyanarayanan >>>> <sathyanarayanan.kuppuswamy@linux.intel.com> >>>> --- >>>> arch/x86/kernel/cpu/intel.c | 7 ++++++- >>>> 1 file changed, 6 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c >>>> index 01d7935feaed..47f0bc95ce2a 100644 >>>> --- a/arch/x86/kernel/cpu/intel.c >>>> +++ b/arch/x86/kernel/cpu/intel.c >>>> @@ -1190,7 +1190,12 @@ static void bus_lock_init(void) >>>> bool handle_user_split_lock(struct pt_regs *regs, long error_code) >>>> { >>>> - if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal) >>>> + /* >>>> + * In virtualization environment, it can get split lock #AC >>>> even when >>>> + * sld_off but hypervisor enables it. >>>> + * Thus only handles when sld_warn explicitly. >>>> + */ >>>> + if ((regs->flags & X86_EFLAGS_AC) || sld_state != sld_warn) >>>> return false; >>>> split_lock_warn(regs->ip); >>>> return true; >>>> -- >>>> 2.25.1 >>>> > -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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