From: Reiji Watanabe <reijiw@google.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Raghavendra Rao Ananta <rananta@google.com>,
kvm@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
Peter Shier <pshier@google.com>,
linux-kernel@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Will Deacon <will@kernel.org>,
kvmarm@lists.cs.columbia.edu,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Jim Mattson <jmattson@google.com>
Subject: Re: [RFC PATCH v3 01/11] KVM: Capture VM start
Date: Tue, 18 Jan 2022 23:47:13 -0800 [thread overview]
Message-ID: <CAAeT=FyJAG1dEFLvrQ4UXrwUqBUhY0AKkjzFpyi74zCJZUEYVg@mail.gmail.com> (raw)
In-Reply-To: <YedWUJNnQK3HFrWC@google.com>
On Tue, Jan 18, 2022 at 4:07 PM Sean Christopherson <seanjc@google.com> wrote:
>
> On Fri, Jan 14, 2022, Reiji Watanabe wrote:
> > The restriction, with which KVM doesn't need to worry about the changes
> > in the registers after KVM_RUN, could potentially protect or be useful
> > to protect KVM and simplify future changes/maintenance of the KVM codes
> > that consumes the values.
>
> That sort of protection is definitely welcome, the previously mentioned CPUID mess
> on x86 would have benefit greatly by KVM being restrictive in the past. That said,
> hooking KVM_RUN is likely the wrong way to go about implementing any restrictions.
> Running a vCPU is where much of the vCPU's state is explicitly consumed, but it's
> all too easy for KVM to implicity/indirectly consume state via a different ioctl(),
> e.g. if there are side effects that are visible in other registers, than an update
> can also be visible to userspace via KVM_{G,S}ET_{S,}REGS, at which point disallowing
> modifying state after KVM_RUN but not after reading/writing regs is arbitrary and
> inconsitent.
Thank you for your comments !
I think I understand your concern, and that's a great point.
That's not the case for those pseudo registers though at least for now :)
BTW, is this concern specific to hooking KVM_RUN ? (Wouldn't it be the
same for the option with "if kvm->created_vcpus > 0" ?)
> If possible, preventing modification if kvm->created_vcpus > 0 is ideal as it's
> a relatively common pattern in KVM, and provides a clear boundary to userpace
> regarding what is/isn't allowed.
Yes, I agree that would be better in general. For (pseudo) registers,
I would think preventing modification if kvm->created_vcpus > 0 might
not be a very good option for KVM/ARM though considering usage of
KVM_GET_REG_LIST and KVM_{G,S}ET_ONE_REG.
Thanks,
Reiji
next prev parent reply other threads:[~2022-01-19 7:47 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-04 19:49 [RFC PATCH v3 00/11] KVM: arm64: Add support for hypercall services selection Raghavendra Rao Ananta
2022-01-04 19:49 ` [RFC PATCH v3 01/11] KVM: Capture VM start Raghavendra Rao Ananta
2022-01-07 6:06 ` Reiji Watanabe
2022-01-07 23:43 ` Raghavendra Rao Ananta
2022-01-08 0:04 ` Jim Mattson
2022-01-10 23:07 ` Raghavendra Rao Ananta
2022-01-10 23:57 ` Jim Mattson
2022-01-11 18:52 ` Raghavendra Rao Ananta
2022-01-11 19:16 ` Jim Mattson
2022-01-12 18:29 ` Raghavendra Rao Ananta
2022-01-13 17:21 ` Sean Christopherson
2022-01-14 0:42 ` Raghavendra Rao Ananta
2022-01-14 1:10 ` Sean Christopherson
2022-01-14 21:51 ` Reiji Watanabe
2022-01-18 22:54 ` Raghavendra Rao Ananta
2022-01-19 0:07 ` Sean Christopherson
2022-01-19 7:47 ` Reiji Watanabe [this message]
2022-01-20 0:27 ` Sean Christopherson
2022-01-20 19:16 ` Raghavendra Rao Ananta
2022-01-25 15:15 ` Marc Zyngier
2022-01-25 15:10 ` Marc Zyngier
2022-01-11 0:03 ` Reiji Watanabe
2022-01-11 18:54 ` Raghavendra Rao Ananta
2022-01-08 1:06 ` Sean Christopherson
2022-01-10 23:23 ` Raghavendra Rao Ananta
2022-01-11 17:36 ` Sean Christopherson
2022-01-11 18:46 ` Raghavendra Rao Ananta
2022-01-11 19:04 ` Sean Christopherson
2022-01-12 18:08 ` Raghavendra Rao Ananta
2022-01-12 18:24 ` Sean Christopherson
2022-01-12 18:31 ` Sean Christopherson
2022-01-04 19:49 ` [RFC PATCH v3 02/11] KVM: arm64: Factor out firmware register handling from psci.c Raghavendra Rao Ananta
2022-01-04 19:49 ` [RFC PATCH v3 03/11] KVM: Introduce KVM_CAP_ARM_HVC_FW_REG_BMAP Raghavendra Rao Ananta
2022-01-08 5:40 ` Reiji Watanabe
2022-01-10 23:40 ` Raghavendra Rao Ananta
2022-01-11 4:33 ` Reiji Watanabe
2022-01-04 19:49 ` [RFC PATCH v3 04/11] KVM: arm64: Setup a framework for hypercall bitmap firmware registers Raghavendra Rao Ananta
2022-01-10 6:28 ` Reiji Watanabe
2022-01-11 0:50 ` Raghavendra Rao Ananta
2022-01-12 5:11 ` Reiji Watanabe
2022-01-12 18:02 ` Raghavendra Rao Ananta
2022-01-14 6:23 ` Reiji Watanabe
2022-01-19 6:42 ` Jason Wang
2022-01-19 10:21 ` Marc Zyngier
2022-01-04 19:49 ` [RFC PATCH v3 05/11] KVM: arm64: Add standard hypervisor firmware register Raghavendra Rao Ananta
2022-01-04 19:49 ` [RFC PATCH v3 06/11] KVM: arm64: Add vendor " Raghavendra Rao Ananta
2022-01-04 19:49 ` [RFC PATCH v3 07/11] Docs: KVM: Add doc for the bitmap firmware registers Raghavendra Rao Ananta
2022-01-04 19:49 ` [RFC PATCH v3 08/11] Docs: KVM: Rename psci.rst to hypercalls.rst Raghavendra Rao Ananta
2022-01-04 19:49 ` [RFC PATCH v3 09/11] tools: Import ARM SMCCC definitions Raghavendra Rao Ananta
2022-01-04 19:49 ` [RFC PATCH v3 10/11] selftests: KVM: aarch64: Introduce hypercall ABI test Raghavendra Rao Ananta
2022-01-04 19:49 ` [RFC PATCH v3 11/11] selftests: KVM: aarch64: Add the bitmap firmware registers to get-reg-list Raghavendra Rao Ananta
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