linux-kernel - Re: [PATCH 2/2] KVM: LAPIC: Don't need to clear IPI delivery status for x2apic

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87eete415a.fsf@vitty.brq.redhat.com>
Date:   Fri, 27 Mar 2020 10:06:57 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH 2/2] KVM: LAPIC: Don't need to clear IPI delivery status for x2apic

Wanpeng Li <kernellwp@...il.com> writes:

> From: Wanpeng Li <wanpengli@...cent.com>
>
> IPI delivery status field is not present for x2apic, don't need 
> to clear IPI delivery status for x2apic.
>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> ---
>  arch/x86/kvm/lapic.c | 3 ++-
>  arch/x86/kvm/x86.c   | 1 -
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 88929b1..f6d69e2 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1942,7 +1942,8 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
>  	}
>  	case APIC_ICR:
>  		/* No delay here, so we always clear the pending bit */

'Always' in the comment above now reads a bit odd, I'd suggest modifying
it to 'Immediately clear Delivery Status field in xAPIC mode' - or just
drop it altogeter.

> -		val &= ~(1 << 12);
> +		if (!apic_x2apic_mode(apic))
> +			val &= ~(1 << 12);
>  		kvm_apic_send_ipi(apic, val, kvm_lapic_get_reg(apic, APIC_ICR2));
>  		kvm_lapic_set_reg(apic, APIC_ICR, val);
>  		break;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 495709f..6ced0e1 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1562,7 +1562,6 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data
>  		((data & APIC_MODE_MASK) == APIC_DM_FIXED) &&
>  		((u32)(data >> 32) != X2APIC_BROADCAST)) {
>  
> -		data &= ~(1 << 12);
>  		kvm_apic_send_ipi(vcpu->arch.apic, (u32)data, (u32)(data >> 32));
>  		kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR2, (u32)(data >> 32));
>  		kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR, (u32)data);

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly