From: Dave Martin <Dave.Martin@arm.com>
To: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Marc Zyngier <Marc.Zyngier@arm.com>,
Catalin Marinas <Catalin.Marinas@arm.com>,
Will Deacon <Will.Deacon@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Kristina Martsenko <Kristina.Martsenko@arm.com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [kvmtool PATCH v6 6/6] arm/kvm: arm64: Add a vcpu feature for pointer authentication
Date: Tue, 5 Mar 2019 11:11:51 +0000 [thread overview]
Message-ID: <20190305111149.GK3567@e103592.cambridge.arm.com> (raw)
In-Reply-To: <b21de5ed-197d-3ea7-021c-b3bca312e70c@arm.com>
On Mon, Mar 04, 2019 at 04:38:18PM +0530, Amit Daniel Kachhap wrote:
>
> Hi Dave,
>
> On 3/1/19 4:54 PM, Dave P Martin wrote:
> >On Fri, Mar 01, 2019 at 10:37:54AM +0000, Amit Daniel Kachhap wrote:
> >>Hi,
> >>
> >>On 2/21/19 9:24 PM, Dave Martin wrote:
> >>>On Tue, Feb 19, 2019 at 02:54:31PM +0530, Amit Daniel Kachhap wrote:
> >
> >[...]
> >
> >>>>diff --git a/arm/aarch64/include/kvm/kvm-config-arch.h b/arm/aarch64/include/kvm/kvm-config-arch.h
> >>>>index 04be43d..2074684 100644
> >>>>--- a/arm/aarch64/include/kvm/kvm-config-arch.h
> >>>>+++ b/arm/aarch64/include/kvm/kvm-config-arch.h
> >>>>@@ -8,7 +8,9 @@
> >>>> "Create PMUv3 device"), \
> >>>> OPT_U64('\0', "kaslr-seed", &(cfg)->kaslr_seed, \
> >>>> "Specify random seed for Kernel Address Space " \
> >>>>- "Layout Randomization (KASLR)"),
> >>>>+ "Layout Randomization (KASLR)"), \
> >>>>+ OPT_BOOLEAN('\0', "ptrauth", &(cfg)->has_ptrauth, \
> >>>>+ "Enable address authentication"),
> >>>
> >>>Nit: doesn't this enable address *and* generic authentication? The
> >>>discussion on what capababilities and enables the ABI exposes probably
> >>>needs to conclude before we can finalise this here.
> >>ok.
> >>>
> >>>However, I would recommend that we provide a single option here that
> >>>turns both address authentication and generic authentication on, even
> >>>if the ABI treats them independently. This is expected to be the common
> >>>case by far.
> >>ok
> >>>
> >>>We can always add more fine-grained options later if it turns out to be
> >>>necessary.
> >>Mark suggested to provide 2 flags [1] for Address and Generic
> >>authentication so I was thinking of adding 2 features like,
> >>
> >>+#define KVM_ARM_VCPU_PTRAUTH_ADDR 4 /* CPU uses pointer address
> >>authentication */
> >>+#define KVM_ARM_VCPU_PTRAUTH_GENERIC 5 /* CPU uses pointer generic
> >>authentication */
> >>
> >>And supply both of them concatenated in VCPU_INIT stage. Kernel KVM
> >>would expect both feature requested together.
> >
> >Seems reasonable. Do you mean the kernel would treat it as an error if
> >only one of these flags is passed to KVM_ARM_VCPU_INIT, or would KVM
> >simply treat them as independent?
> If both flags are passed together then only start using ptrauth otherwise
> keep ptrauth disabled. This is just to finalize the user side abi as of now
> and KVM can be updated later.
If just flag is passed, I think KVM_ARM_VCPU_INIT should just fail.
Otherwise we risk userspace becoming accidentally reliant on behaviour
that may change in the future.
Cheers
---Dave
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next prev parent reply other threads:[~2019-03-05 11:12 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-19 9:24 [PATCH v6 0/6] Add ARMv8.3 pointer authentication for kvm guest Amit Daniel Kachhap
2019-02-19 9:24 ` [PATCH v6 1/6] arm64/kvm: preserve host HCR_EL2 value Amit Daniel Kachhap
2019-02-21 11:50 ` Mark Rutland
2019-02-25 18:09 ` Marc Zyngier
2019-02-28 6:43 ` Amit Daniel Kachhap
2019-02-21 15:49 ` Dave Martin
2019-03-01 5:56 ` Amit Daniel Kachhap
2019-02-25 17:39 ` James Morse
2019-02-26 10:06 ` James Morse
2019-03-02 11:09 ` Amit Daniel Kachhap
2019-02-19 9:24 ` [PATCH v6 2/6] arm64/kvm: preserve host MDCR_EL2 value Amit Daniel Kachhap
2019-02-21 11:57 ` Mark Rutland
2019-02-21 15:51 ` Dave Martin
2019-03-01 6:10 ` Amit Daniel Kachhap
2019-02-19 9:24 ` [PATCH v6 3/6] arm64/kvm: context-switch ptrauth registers Amit Daniel Kachhap
2019-02-21 12:29 ` Mark Rutland
2019-02-21 15:51 ` Dave Martin
2019-03-01 6:17 ` Amit Daniel Kachhap
2019-02-28 9:07 ` Amit Daniel Kachhap
2019-02-21 15:53 ` Dave Martin
2019-03-01 9:35 ` Amit Daniel Kachhap
2019-02-26 18:31 ` James Morse
2019-03-04 10:51 ` Amit Daniel Kachhap
2019-02-19 9:24 ` [PATCH v6 4/6] arm64/kvm: add a userspace option to enable pointer authentication Amit Daniel Kachhap
2019-02-21 12:34 ` Mark Rutland
2019-02-28 9:25 ` Amit Daniel Kachhap
2019-02-21 15:53 ` Dave Martin
2019-03-01 9:41 ` Amit Daniel Kachhap
2019-03-01 12:22 ` Dave P Martin
2019-02-26 18:33 ` James Morse
2019-03-04 10:56 ` Amit Daniel Kachhap
2019-02-19 9:24 ` [PATCH v6 5/6] arm64/kvm: control accessibility of ptrauth key registers Amit Daniel Kachhap
2019-02-21 15:53 ` Dave Martin
2019-02-26 18:34 ` James Morse
2019-02-19 9:24 ` [kvmtool PATCH v6 6/6] arm/kvm: arm64: Add a vcpu feature for pointer authentication Amit Daniel Kachhap
2019-02-21 15:54 ` Dave Martin
2019-03-01 10:37 ` Amit Daniel Kachhap
2019-03-01 11:24 ` Dave P Martin
2019-03-04 11:08 ` Amit Daniel Kachhap
2019-03-05 11:11 ` Dave Martin [this message]
2019-02-26 18:03 ` [PATCH v6 0/6] Add ARMv8.3 pointer authentication for kvm guest James Morse
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