From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Siddharth Chandrasekaran <sidcha@amazon.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kys@microsoft.com, haiyangz@microsoft.com,
sthemmin@microsoft.com, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, x86@kernel.org, hpa@zytor.com, seanjc@google.com,
wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org,
graf@amazon.com, eyakovl@amazon.de, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Wei Liu <wei.liu@kernel.org>
Subject: Re: [PATCH 0/4] Add support for XMM fast hypercalls
Date: Fri, 09 Apr 2021 09:42:41 +0200 [thread overview]
Message-ID: <87wntb7vke.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20210408174521.GF32315@u366d62d47e3651.ant.amazon.com>
Siddharth Chandrasekaran <sidcha@amazon.de> writes:
> On Thu, Apr 08, 2021 at 04:30:18PM +0000, Wei Liu wrote:
>> On Thu, Apr 08, 2021 at 05:54:43PM +0200, Siddharth Chandrasekaran wrote:
>> > On Thu, Apr 08, 2021 at 05:48:19PM +0200, Paolo Bonzini wrote:
>> > > On 08/04/21 17:40, Siddharth Chandrasekaran wrote:
>> > > > > > > Although the Hyper-v TLFS mentions that a guest cannot use this feature
>> > > > > > > unless the hypervisor advertises support for it, some hypercalls which
>> > > > > > > we plan on upstreaming in future uses them anyway.
>> > > > > > No, please don't do this. Check the feature bit(s) before you issue
>> > > > > > hypercalls which rely on the extended interface.
>> > > > > Perhaps Siddharth should clarify this, but I read it as Hyper-V being
>> > > > > buggy and using XMM arguments unconditionally.
>> > > > The guest is at fault here as it expects Hyper-V to consume arguments
>> > > > from XMM registers for certain hypercalls (that we are working) even if
>> > > > we didn't expose the feature via CPUID bits.
>> > >
>> > > What guest is that?
>> >
>> > It is a Windows Server 2016.
>>
>> Can you be more specific? Are you implementing some hypercalls from
>> TLFS? If so, which ones?
>
> Yes all of them are from TLFS. We are implementing VSM and there are a
> bunch of hypercalls that we have implemented to manage VTL switches,
> memory protection and virtual interrupts.
Wow, sounds awesome! Do you plan to upstream this work?
> The following 3 hypercalls that use the XMM fast hypercalls are relevant
> to this patch set:
>
> HvCallModifyVtlProtectionMask
> HvGetVpRegisters
> HvSetVpRegisters
It seems AccessVSM and AccessVpRegisters privilges have implicit
dependency on XMM input/output. This will need to be enforced in KVM
userspace.
--
Vitaly
next prev parent reply other threads:[~2021-04-09 7:42 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-07 21:29 [PATCH 0/4] Add support for XMM fast hypercalls Siddharth Chandrasekaran
2021-04-08 15:28 ` Wei Liu
2021-04-08 15:30 ` Paolo Bonzini
2021-04-08 15:38 ` Wei Liu
2021-04-08 16:21 ` Siddharth Chandrasekaran
2021-04-08 15:40 ` Siddharth Chandrasekaran
2021-04-08 15:48 ` Paolo Bonzini
2021-04-08 15:54 ` Siddharth Chandrasekaran
2021-04-08 16:30 ` Wei Liu
2021-04-08 17:45 ` Siddharth Chandrasekaran
2021-04-09 7:42 ` Vitaly Kuznetsov [this message]
2021-04-09 7:59 ` Siddharth Chandrasekaran
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