From: Sean Christopherson <seanjc@google.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Maxim Levitsky <mlevitsk@redhat.com>,
kvm@vger.kernel.org, Wanpeng Li <wanpengli@tencent.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Joerg Roedel <joro@8bytes.org>,
linux-kernel@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Jim Mattson <jmattson@google.com>,
x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] KVM: x86: fix a typo in __try_cmpxchg_user that caused cmpxchg to be not atomic
Date: Thu, 12 May 2022 13:48:24 +0000 [thread overview]
Message-ID: <Yn0QKHKKibBP2V0F@google.com> (raw)
In-Reply-To: <875ymayl55.fsf@redhat.com>
On Thu, May 12, 2022, Vitaly Kuznetsov wrote:
> Maxim Levitsky <mlevitsk@redhat.com> writes:
>
> > Fixes: 1c2361f667f36 ("KVM: x86: Use __try_cmpxchg_user() to emulate atomic accesses")
> > Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> > ---
> > arch/x86/kvm/x86.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Yes, this is the root cause of the TDP mmu leak I was doing debug of in the last week.
> > Non working cmpxchg on which TDP mmu relies makes it install two differnt shadow pages
> > under same spte.
Ewww, as in running a buggy L0 resulted in a CMPXCHG going sideways in L1? That's
awful. My apologies :-(
> In case the fix is not squashed with 1c2361f667f36, the above should
> really go before '---'.
>
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 8ee8c91fa7625..79cabd3d97d22 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -7329,7 +7329,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
> > goto emul_write;
> >
> > hva = kvm_vcpu_gfn_to_hva(vcpu, gpa_to_gfn(gpa));
> > - if (kvm_is_error_hva(addr))
> > + if (kvm_is_error_hva(hva))
>
> Looks like a typo indeed, so
>
> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Yep, if this doesn't get squashed
Reviewed-by: Sean Christopherson <seanjc@google.com>
next prev parent reply other threads:[~2022-05-12 13:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-02 0:49 [PATCH v2 0/5] x86: uaccess CMPXCHG + KVM bug fixes Sean Christopherson
2022-02-02 0:49 ` [PATCH v2 1/5] Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug Sean Christopherson
2022-02-02 0:49 ` [PATCH v2 2/5] x86/uaccess: Implement macros for CMPXCHG on user addresses Sean Christopherson
2022-02-02 0:49 ` [PATCH v2 3/5] KVM: x86: Use __try_cmpxchg_user() to update guest PTE A/D bits Sean Christopherson
2022-02-02 0:49 ` [PATCH v2 4/5] KVM: x86: Use __try_cmpxchg_user() to emulate atomic accesses Sean Christopherson
2022-05-12 10:14 ` [PATCH] KVM: x86: fix a typo in __try_cmpxchg_user that caused cmpxchg to be not atomic Maxim Levitsky
2022-05-12 12:45 ` Vitaly Kuznetsov
2022-05-12 13:48 ` Sean Christopherson [this message]
2022-05-12 15:47 ` Paolo Bonzini
2022-05-12 21:27 ` Sean Christopherson
2022-05-16 13:14 ` Maxim Levitsky
2022-05-16 14:03 ` Sean Christopherson
2022-02-02 0:49 ` [PATCH v2 5/5] KVM: x86: Bail to userspace if emulation of atomic user access faults Sean Christopherson
2022-04-01 7:53 ` [PATCH v2 0/5] x86: uaccess CMPXCHG + KVM bug fixes Paolo Bonzini
2022-04-01 17:07 ` Tadeusz Struk
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