linux-kernel - Re: [RFC PATCH 18/18] x86: request TLB flush to slave CPU using NMI

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: <4FEC88A2.5040103@redhat.com>
Date:	Thu, 28 Jun 2012 19:38:58 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
	yrl.pp-manager.tt@...achi.com,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC PATCH 18/18] x86: request TLB flush to slave CPU using NMI

On 06/28/2012 09:08 AM, Tomoki Sekiyama wrote:
> For slave CPUs, it is inapropriate to request TLB flush using IPI.
> because the IPI may be sent to a KVM guest when the slave CPU is running
> the guest with direct interrupt routing.
> 
> Instead, it registers a TLB flush request in per-cpu bitmask and send a NMI
> to interrupt execution of the guest. Then, NMI handler will check the
> requests and handles the requests.


Currently x86's get_user_pages_fast() depends on TLB flushes being held
up by local_irq_disable().  With this patch, this is no longer true and
get_user_pages_fast() can race with page table freeing.  There are
patches from Peter Zijlstra to remove this dependency though.  NMIs are
still slow and fragile when compared to normal interrupts, so this patch
is somewhat problematic.


-- 
error compiling committee.c: too many arguments to function


--
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/