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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id b134sm39188403wmd.26.2019.03.26.06.48.52 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 26 Mar 2019 06:48:53 -0700 (PDT) From: Vitaly Kuznetsov To: Liran Alon Cc: kvm@vger.kernel.org, Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Jon Doron , Sean Christopherson , linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: x86: nVMX: allow RSM to restore VMXE CR4 flag In-Reply-To: References: <20190326130746.28748-1-vkuznets@redhat.com> Date: Tue, 26 Mar 2019 14:48:52 +0100 Message-ID: <87k1glagqj.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Liran Alon writes: >> On 26 Mar 2019, at 15:07, Vitaly Kuznetsov wrote: >> >> Commit 5bea5123cbf0 ("KVM: VMX: check nested state and CR4.VMXE against >> SMM") introduced a check to vmx_set_cr4() forbidding to set VMXE from SMM. >> The check is correct, however, there is a special case when RSM is called >> to leave SMM: rsm_enter_protected_mode() is called with HF_SMM_MASK still >> set and in case VMXE was set before entering SMM we're failing to return. >> >> Resolve the issue by temporary dropping HF_SMM_MASK around set_cr4() calls >> when ops->set_cr() is called from RSM. >> >> Reported-by: Jon Doron >> Suggested-by: Liran Alon >> Fixes: 5bea5123cbf0 ("KVM: VMX: check nested state and CR4.VMXE against SMM") >> Signed-off-by: Vitaly Kuznetsov > > Patch looks good to me. > Reviewed-by: Liran Alon Thanks! > >> --- >> - Instread of putting the temporary HF_SMM_MASK drop to >> rsm_enter_protected_mode() (as was suggested by Liran), move it to >> emulator_set_cr() modifying its interface. emulate.c seems to be >> vcpu-specifics-free at this moment, we may want to keep it this way. >> - It seems that Hyper-V+UEFI on KVM is still broken, I'm observing sporadic >> hangs even with this patch. These hangs, however, seem to be unrelated to >> rsm. > > Feel free to share details on these hangs ;) > You've asked for it) The immediate issue I'm observing is some sort of a lockup which is easy to trigger with e.g. "-usb -device usb-tablet" on Qemu command line; it seems we get too many interrupts and combined with preemtion timer for L2 we're not making any progress: kvm_userspace_exit: reason KVM_EXIT_IOAPIC_EOI (26) kvm_set_irq: gsi 18 level 1 source 0 kvm_msi_set_irq: dst 0 vec 177 (Fixed|physical|level) kvm_apic_accept_irq: apicid 0 vec 177 (Fixed|edge) kvm_fpu: load kvm_entry: vcpu 0 kvm_exit: reason VMRESUME rip 0xfffff80000848115 info 0 0 kvm_entry: vcpu 0 kvm_exit: reason PREEMPTION_TIMER rip 0xfffff800f4448e01 info 0 0 kvm_nested_vmexit: rip fffff800f4448e01 reason PREEMPTION_TIMER info1 0 info2 0 int_info 0 int_info_err 0 kvm_nested_vmexit_inject: reason EXTERNAL_INTERRUPT info1 0 info2 0 int_info 800000b1 int_info_err 0 kvm_entry: vcpu 0 kvm_exit: reason APIC_ACCESS rip 0xfffff8000081fe11 info 10b0 0 kvm_apic: apic_write APIC_EOI = 0x0 kvm_eoi: apicid 0 vector 177 kvm_fpu: unload kvm_userspace_exit: reason KVM_EXIT_IOAPIC_EOI (26) ... (and the pattern repeats) Maybe it is a usb-only/Qemu-only problem, maybe not. -- Vitaly