From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Isaku Yamahata <isaku.yamahata@intel.com>
Subject: Re: [PATCH 7/7] KVM: VMX: Introduce test mode related to EPT violation VE
Date: Sat, 18 May 2024 00:05:01 +0200 [thread overview]
Message-ID: <CABgObfYwxN7yoRUDfYVPb57=p90nUqfW9+y_=Ndeg4oXKaZNQg@mail.gmail.com> (raw)
In-Reply-To: <ZkefU_PhjvnaEE7Q@google.com>
On Fri, May 17, 2024 at 8:18 PM Sean Christopherson <seanjc@google.com> wrote:
> > Ok, so it does look like a CPU issue. Even with the fixes you identified, I
> > don't see any other solution than adding scary text in Kconfig, defaulting
> > it to "n", and adding an also-very-scary pr_err_once("...") the first time
> > VMPTRLD is executed with CONFIG_KVM_INTEL_PROVE_VE.
>
> I don't think we need to make it super scary, at least not yet. KVM just needs
> to not kill the VM, which thanks to the BUSY flag is trivial: just resume the guest.
> Then the failure is "just" a WARN, which won't be anywhere near as problematic for
> KVM developers.
>
> If we don't have a resolution by rc6 or so, then maybe consider doing something
> more drastic?
>
> I agree that it should be off by default though. And the help text should be
> more clear that this intended only for developers and testing environments.
>
> I have a handful of patches, including one to not kill the VM. I'll try to post
> them later today, mostly just need to write changelogs.
>
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index 75082c4a9ac4..5c22186671e9 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -98,15 +98,15 @@ config KVM_INTEL
>
> config KVM_INTEL_PROVE_VE
> bool "Check that guests do not receive #VE exceptions"
> - default KVM_PROVE_MMU || DEBUG_KERNEL
> - depends on KVM_INTEL
> + depends on KVM_INTEL && KVM_PROVE_MMU
> help
"depends on KVM_PROVE_MMU" is wrong, I think. I'd like to keep it
enabled without slowing down too much the VMs, for example.
On the other hand "default DEBUG_KERNEL" is definitely too heavy
with these CPU issues.
Paolo
prev parent reply other threads:[~2024-05-17 22:05 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 15:44 [PATCH 0/7] KVM: MMU changes for TDX VE support Paolo Bonzini
2024-05-07 15:44 ` [PATCH 1/7] KVM: Allow page-sized MMU caches to be initialized with custom 64-bit values Paolo Bonzini
2024-05-07 15:44 ` [PATCH 2/7] KVM: x86/mmu: Replace hardcoded value 0 for the initial value for SPTE Paolo Bonzini
2024-05-15 17:32 ` Isaku Yamahata
2024-05-15 17:33 ` Paolo Bonzini
2024-05-07 15:44 ` [PATCH 3/7] KVM: x86/mmu: Allow non-zero value for non-present SPTE and removed SPTE Paolo Bonzini
2024-05-07 15:44 ` [PATCH 4/7] KVM: x86/mmu: Add Suppress VE bit to EPT shadow_mmio_mask/shadow_present_mask Paolo Bonzini
2024-05-07 15:44 ` [PATCH 5/7] KVM: x86/mmu: Track shadow MMIO value on a per-VM basis Paolo Bonzini
2024-05-07 15:44 ` [PATCH 6/7] KVM, x86: add architectural support code for #VE Paolo Bonzini
2024-05-07 15:44 ` [PATCH 7/7] KVM: VMX: Introduce test mode related to EPT violation VE Paolo Bonzini
2024-05-15 23:38 ` Sean Christopherson
2024-05-17 1:40 ` Sean Christopherson
2024-05-17 9:56 ` Isaku Yamahata
2024-05-17 16:35 ` Sean Christopherson
2024-05-17 16:35 ` Paolo Bonzini
2024-05-17 16:38 ` Sean Christopherson
2024-05-17 17:09 ` Paolo Bonzini
2024-05-17 18:17 ` Sean Christopherson
2024-05-17 22:05 ` Paolo Bonzini [this message]
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