From: Wei Liu <wei.liu@kernel.org>
To: Siddharth Chandrasekaran <sidcha@amazon.de>
Cc: kys@microsoft.com, haiyangz@microsoft.com,
sthemmin@microsoft.com, wei.liu@kernel.org, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.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
Subject: Re: [PATCH 0/4] Add support for XMM fast hypercalls
Date: Thu, 8 Apr 2021 15:28:17 +0000 [thread overview]
Message-ID: <20210408152817.k4d4hjdqu7hsjllo@liuwe-devbox-debian-v2> (raw)
In-Reply-To: <20210407212926.3016-1-sidcha@amazon.de>
On Wed, Apr 07, 2021 at 11:29:26PM +0200, Siddharth Chandrasekaran wrote:
> Hyper-V supports the use of XMM registers to perform fast hypercalls.
> This allows guests to take advantage of the improved performance of the
> fast hypercall interface even though a hypercall may require more than
> (the current maximum of) two general purpose registers.
>
> The XMM fast hypercall interface uses an additional six XMM registers
> (XMM0 to XMM5) to allow the caller to pass an input parameter block of
> up to 112 bytes. Hyper-V can also return data back to the guest in the
> remaining XMM registers that are not used by the current hypercall.
>
> 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.
Wei.
next prev parent reply other threads:[~2021-04-08 15:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-07 21:29 Siddharth Chandrasekaran
2021-04-08 15:28 ` Wei Liu [this message]
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
2021-04-09 7:59 ` Siddharth Chandrasekaran
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