Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [patch 2/2] x86/kvm/vmx: Prevent split lock detection induced #AC wreckage | Date | Thu, 02 Apr 2020 18:56:57 +0200 |
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Sean Christopherson <sean.j.christopherson@intel.com> writes: > On Thu, Apr 02, 2020 at 02:33:00PM +0200, Thomas Gleixner wrote: >> Mark the module with MOD_INFO(sld_safe, "Y") so the module loader does not >> force SLD off. > > Some comments below. But, any objection to taking Xiaoyao's patches that > do effectively the same things, minus the MOD_INFO()? I'll repost them in > reply to this thread.
If they are sane, I don't have a problem. But TBH, I really couldn't be bothered to actually scan my mails whether there surfaced something sane by now. Writing that up was just faster :)
I'll have look.
>> +static bool guest_handles_ac(struct kvm_vcpu *vcpu) >> +{ >> + /* >> + * If guest has alignment checking enabled in CR0 and activated in >> + * eflags, then the #AC originated from CPL3 and the guest is able >> + * to handle it. It does not matter whether this is a regular or >> + * a split lock operation induced #AC. >> + */ >> + if (vcpu->arch.cr0 & X86_CR0_AM && > > Technically not required since KVM doesn't let the gets toggle CR0.AM at > will, but going through kvm_read_cr0{_bits}() is preferred.
You're the expert here.
>> + vmx_get_rflags(vcpu) & X86_EFLAGS_AC) > > I don't think this is correct. A guest could trigger a split-lock #AC at > CPL0 with EFLAGS.AC=1 and CR0.AM=1, and then panic because it didn't expect > #AC at CPL0.
Indeed.
Thanks,
tglx
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