linux-kernel - Re: [PATCH] KVM: x86: inline kvm_ioapic_handles

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] [day] [month] [year] [list]

Date:	Mon, 23 Mar 2015 21:17:44 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Radim Krčmář <rkrcmar@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH] KVM: x86: inline kvm_ioapic_handles_vector()

On Thu, Mar 19, 2015 at 09:52:41PM +0100, Radim Krčmář wrote:
> An overhead from function call is not appropriate for its size and
> frequency of execution.
> 
> Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
> ---
>   I'm not very fond of that smp_rmb(): there is no real synchronization
>   against update_handled_vectors(), 

Yes, because the guest OS should provide synchronization (it should
shutdown interrupts before attempting to modify IOAPIC table).

The smp_wmb is necessary.

>  so the only point I see is to drop
>   cached value of handled_vectors, which seems like bad use of LFENCE.

test_bit has volatile on *addr, so don't see why the smp_rmb is
necessary at all.

Applied, thanks.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/