From: Andrew Jones <drjones@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Peter Maydell <Peter.Maydell@arm.com>,
Juan Quintela <quintela@redhat.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Richard Henderson <richard.henderson@linaro.org>,
QEMU Developers <qemu-devel@nongnu.org>,
lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Marc Zyngier <maz@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Price <steven.price@arm.com>,
Will Deacon <will@kernel.org>,
kvmarm@lists.cs.columbia.edu,
arm-mail-list <linux-arm-kernel@lists.infradead.org>,
Dave Martin <Dave.Martin@arm.com>
Subject: Re: [PATCH v2 2/2] arm64: kvm: Introduce MTE VCPU feature
Date: Thu, 10 Sep 2020 08:38:54 +0200 [thread overview]
Message-ID: <20200910063854.vwhtn3lc5tei72fh@kamzik.brq.redhat.com> (raw)
In-Reply-To: <CAFEAcA_1YnBg3HVmtrSMP8u7GqHY8mtDAJwVcZuNUhwA+q9q=w@mail.gmail.com>
On Wed, Sep 09, 2020 at 04:53:02PM +0100, Peter Maydell wrote:
> On Wed, 9 Sep 2020 at 16:48, Andrew Jones <drjones@redhat.com> wrote:
> > We either need a KVM cap or a new CPU feature probing interface to avoid
> > making userspace try features one at a time. It's too bad that VCPU_INIT
> > doesn't clear all offending features from the feature set when returning
> > EINVAL, because then userspace could create a scratch VCPU with everything
> > it supports in order to see what KVM also supports in one go.
>
> You could add one if you wanted -- add a new feature bit
> TELL_ME_WHAT_YOU_HAVE. If the kernel sees that then on filure
> it clears out feature bits it doesn't support and also clears
> TELL_ME_WHAT_YOU_HAVE. If QEMU sees EINVAL and TELL_ME_WHAT_YOU_HAVE
> is still set, then it knows it's dealing with an old kernel
> and has to do one-at-a-time probing. If it sees EINVAL but not
> TELL_ME_WHAT_YOU_HAVE then it knows it has a new kernel and
> has just got all the info.
>
That's a great proposal. I'll try to find time to send the patches.
Thanks,
drew
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next prev parent reply other threads:[~2020-09-10 6:40 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-04 16:00 [PATCH v2 0/2] MTE support for KVM guest Steven Price
2020-09-04 16:00 ` [PATCH v2 1/2] arm64: kvm: Save/restore MTE registers Steven Price
2020-09-04 16:00 ` [PATCH v2 2/2] arm64: kvm: Introduce MTE VCPU feature Steven Price
2020-09-09 15:48 ` Andrew Jones
2020-09-09 15:53 ` Peter Maydell
2020-09-10 6:38 ` Andrew Jones [this message]
2020-09-10 10:01 ` Andrew Jones
2020-09-10 9:21 ` Steven Price
2020-09-10 11:49 ` Andrew Jones
2020-09-07 15:28 ` [PATCH v2 0/2] MTE support for KVM guest Dr. David Alan Gilbert
2020-09-09 9:15 ` Steven Price
2020-09-09 15:25 ` Andrew Jones
2020-09-09 16:04 ` Steven Price
2020-09-10 6:29 ` Andrew Jones
2020-09-10 9:21 ` Steven Price
2020-09-10 13:56 ` Andrew Jones
2020-09-10 14:14 ` Steven Price
2020-09-10 1:45 ` Richard Henderson
2020-09-10 5:44 ` Andrew Jones
2020-09-10 13:27 ` Dr. David Alan Gilbert
2020-09-10 13:39 ` Andrew Jones
2020-09-10 0:33 ` Richard Henderson
2020-09-10 10:24 ` Steven Price
2020-09-10 15:36 ` Richard Henderson
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