From: Will Deacon <will.deacon@arm.com>
To: zichao <zhichao.huang@linaro.org>
Cc: Marc Zyngier <Marc.Zyngier@arm.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
"christoffer.dall@linaro.org" <christoffer.dall@linaro.org>,
"alex.bennee@linaro.org" <alex.bennee@linaro.org>,
"huangzhichao@huawei.com" <huangzhichao@huawei.com>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH v2 01/11] KVM: arm: plug guest debug exploit
Date: Tue, 16 Jun 2015 17:49:15 +0100 [thread overview]
Message-ID: <20150616164914.GM30522@arm.com> (raw)
In-Reply-To: <557DA811.8090705@linaro.org>
On Sun, Jun 14, 2015 at 05:13:05PM +0100, zichao wrote:
> I and marc are talking about how to plug the guest debug exploit in an
> easier way.
>
> I remembered that you mentioned disabling monitor mode had proven to be
> extremely fragile in practice on 32-bit ARM SoCs, what if I save/restore
> the debug monitor mode on each switch between the guest and the host,
> would it be acceptable?
If you're just referring to DBGDSCRext, then you could give it a go, but
you'll certainly want to predicate any writes to that register on whether
or not hw_breakpoint managed to reset the debug regs on the host.
Like I said, accessing these registers always worries me, so I'd really
avoid it in KVM if you can. If not, you'll need to do extensive testing
on a bunch of platforms with and without the presence of external debug.
Will
WARNING: multiple messages have this Message-ID (diff)
From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 01/11] KVM: arm: plug guest debug exploit
Date: Tue, 16 Jun 2015 17:49:15 +0100 [thread overview]
Message-ID: <20150616164914.GM30522@arm.com> (raw)
In-Reply-To: <557DA811.8090705@linaro.org>
On Sun, Jun 14, 2015 at 05:13:05PM +0100, zichao wrote:
> I and marc are talking about how to plug the guest debug exploit in an
> easier way.
>
> I remembered that you mentioned disabling monitor mode had proven to be
> extremely fragile in practice on 32-bit ARM SoCs, what if I save/restore
> the debug monitor mode on each switch between the guest and the host,
> would it be acceptable?
If you're just referring to DBGDSCRext, then you could give it a go, but
you'll certainly want to predicate any writes to that register on whether
or not hw_breakpoint managed to reset the debug regs on the host.
Like I said, accessing these registers always worries me, so I'd really
avoid it in KVM if you can. If not, you'll need to do extensive testing
on a bunch of platforms with and without the presence of external debug.
Will
next prev parent reply other threads:[~2015-06-16 16:49 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-31 4:27 [PATCH v2 00/11] KVM: arm: debug infrastructure support Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-05-31 4:27 ` [PATCH v2 01/11] KVM: arm: plug guest debug exploit Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-06-01 10:56 ` Marc Zyngier
2015-06-01 10:56 ` Marc Zyngier
2015-06-07 13:40 ` zichao
2015-06-07 13:40 ` zichao
2015-06-09 10:29 ` Marc Zyngier
2015-06-09 10:29 ` Marc Zyngier
2015-06-14 16:08 ` zichao
2015-06-14 16:08 ` zichao
2015-06-14 16:13 ` zichao
2015-06-14 16:13 ` zichao
2015-06-16 16:49 ` Will Deacon [this message]
2015-06-16 16:49 ` Will Deacon
2015-05-31 4:27 ` [PATCH v2 02/11] KVM: arm: rename pm_fake handler to trap_raz_wi Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-06-09 10:42 ` Alex Bennée
2015-06-09 10:42 ` Alex Bennée
2015-05-31 4:27 ` [PATCH v2 03/11] KVM: arm: enable to use the ARM_DSCR_MDBGEN macro from KVM assembly code Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-06-09 13:42 ` Alex Bennée
2015-06-09 13:42 ` Alex Bennée
2015-05-31 4:27 ` [PATCH v2 04/11] KVM: arm: common infrastructure for handling AArch32 CP14/CP15 Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-06-09 10:45 ` Alex Bennée
2015-06-09 10:45 ` Alex Bennée
2015-06-14 16:17 ` zichao
2015-06-14 16:17 ` zichao
2015-05-31 4:27 ` [PATCH v2 05/11] KVM: arm: check ordering of all system register tables Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-06-10 13:52 ` Alex Bennée
2015-06-10 13:52 ` Alex Bennée
2015-06-14 16:18 ` zichao
2015-06-14 16:18 ` zichao
2015-05-31 4:27 ` [PATCH v2 06/11] KVM: arm: add trap handlers for 32-bit debug registers Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-05-31 4:27 ` [PATCH v2 07/11] KVM: arm: add trap handlers for 64-bit " Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-05-31 4:27 ` [PATCH v2 08/11] KVM: arm: implement dirty bit mechanism for " Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-05-31 4:27 ` [PATCH v2 09/11] KVM: arm: disable debug mode if we don't actually need it Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-06-01 10:16 ` Will Deacon
2015-06-01 10:16 ` Will Deacon
2015-06-07 14:08 ` zichao
2015-06-07 14:08 ` zichao
2015-05-31 4:27 ` [PATCH v2 10/11] KVM: arm: implement lazy world switch for debug registers Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
2015-05-31 4:27 ` [PATCH v2 11/11] KVM: arm: enable trapping of all " Zhichao Huang
2015-05-31 4:27 ` Zhichao Huang
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