From: Oliver Upton <oliver.upton@linux.dev>
To: Sean Christopherson <seanjc@google.com>
Cc: Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
kvmarm@lists.linux.dev, Akihiko Odaki <akihiko.odaki@daynix.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Raghavendra Rao Ananta <rananta@google.com>,
linux-arm-kernel@lists.infradead.org,
Salil Mehta <salil.mehta@huawei.com>
Subject: Re: [RFC PATCH v2 5/6] KVM: arm64: Add support for KVM_EXIT_HYPERCALL
Date: Mon, 13 Feb 2023 19:24:03 +0000 [thread overview]
Message-ID: <Y+qOUw+j/QFptsIF@linux.dev> (raw)
In-Reply-To: <Y+pe2T2uK2efUNve@google.com>
On Mon, Feb 13, 2023 at 04:01:29PM +0000, Sean Christopherson wrote:
> On Sat, Feb 11, 2023, Oliver Upton wrote:
> > Finally, we need a flag to let userspace know what conduit instruction
> > was used (i.e. SMC vs. HVC). Redefine the remaining padding in
> > kvm_run::hypercall to accomplish this. Let's all take a moment
> > to admire the flowers and see how 'longmode' tied up a full u32 in the
> > UAPI. Weep.
>
> I don't think it has to, at least not for other architectures.
And surrender the opportunity to write a smartass commit message? I
think not.
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 55155e262646..7d3ad820d55c 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -341,8 +341,14 @@ struct kvm_run {
> __u64 nr;
> __u64 args[6];
> __u64 ret;
> - __u32 longmode;
> - __u32 pad;
> + union {
> + /*
> + * Long Mode, a.k.a. 64-bit mode, takes up the
> + * first 32 flags on x86 (historical sludge).
> + */
> + __u32 longmode;
> + __u64 flags;
> + };
You could pull further shenanigans with the x86 residue by guarding
longmode with #ifndef __KERNEL__ and using a macro to raise the
'longmode' flag.
Then we can all pretend it never existed :)
--
Thanks,
Oliver
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next prev parent reply other threads:[~2023-02-13 19:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-11 1:37 [RFC PATCH v2 0/6] KVM: arm64: Userspace SMCCC call filtering Oliver Upton
2023-02-11 1:37 ` [RFC PATCH v2 1/6] KVM: arm64: Add a helper to check if a VM has ran once Oliver Upton
2023-02-13 15:36 ` Sean Christopherson
2023-02-13 15:49 ` Marc Zyngier
2023-02-11 1:37 ` [RFC PATCH v2 2/6] KVM: arm64: Add vm fd device attribute accessors Oliver Upton
2023-02-11 1:37 ` [RFC PATCH v2 3/6] KVM: arm64: Refactor hvc filtering to support different actions Oliver Upton
2023-02-11 1:37 ` [RFC PATCH v2 4/6] KVM: arm64: Use a maple tree to represent the SMCCC filter Oliver Upton
2023-02-11 1:37 ` [RFC PATCH v2 5/6] KVM: arm64: Add support for KVM_EXIT_HYPERCALL Oliver Upton
2023-02-13 16:01 ` Sean Christopherson
2023-02-13 19:24 ` Oliver Upton [this message]
2023-02-24 15:12 ` James Morse
2023-02-24 21:42 ` Oliver Upton
2023-02-11 1:37 ` [RFC PATCH v2 6/6] KVM: arm64: Indroduce support for userspace SMCCC filtering Oliver Upton
2023-02-17 18:35 ` Oliver Upton
2023-02-24 15:12 ` [RFC PATCH v2 0/6] KVM: arm64: Userspace SMCCC call filtering James Morse
2023-02-24 21:32 ` Oliver Upton
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