From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Siddharth Chandrasekaran <sidcha@amazon.de>
Cc: Alexander Graf <graf@amazon.com>,
Evgeny Iakovlev <eyakovl@amazon.de>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Sean Christopherson <seanjc@google.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 3/4] KVM: x86: kvm_hv_flush_tlb use inputs from XMM registers
Date: Thu, 08 Apr 2021 14:52:16 +0200 [thread overview]
Message-ID: <878s5t7xbz.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <01fc0ac9-f159-d3df-6c8c-8f8122fe31ea@redhat.com>
Paolo Bonzini <pbonzini@redhat.com> writes:
> On 08/04/21 14:01, Vitaly Kuznetsov wrote:
>>
>> Also, we can probably defer kvm_hv_hypercall_read_xmm() until we know
>> how many regs we actually need to not read them all (we will always
>> need xmm[0] I guess so we can as well read it here).
>
> The cost is get/put FPU, so I think there's not much to gain from that.
>
Maybe, I just think that in most cases we will only need xmm0. To make
the optimization work we can probably do kvm_get_fpu() once we figured
out that we're dealing with XMM hypercall and do kvm_put_fpu() when
we're done processing hypercall parameters. This way we don't need to do
get/put twice. We can certainly leave this idea to the (possible) future
optimizations.
--
Vitaly
next prev parent reply other threads:[~2021-04-08 12:52 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210407211954.32755-1-sidcha@amazon.de>
2021-04-07 21:19 ` [PATCH 1/4] KVM: x86: Move FPU register accessors into fpu.h Siddharth Chandrasekaran
2021-04-07 21:19 ` [PATCH 2/4] KVM: hyper-v: Collect hypercall params into struct Siddharth Chandrasekaran
2021-04-07 21:19 ` [PATCH 3/4] KVM: x86: kvm_hv_flush_tlb use inputs from XMM registers Siddharth Chandrasekaran
2021-04-08 12:01 ` Vitaly Kuznetsov
2021-04-08 12:37 ` Paolo Bonzini
2021-04-08 12:52 ` Vitaly Kuznetsov [this message]
2021-04-07 21:19 ` [PATCH 4/4] KVM: hyper-v: Advertise support for fast XMM hypercalls Siddharth Chandrasekaran
2021-04-08 12:05 ` Vitaly Kuznetsov
2021-04-08 14:20 ` Siddharth Chandrasekaran
2021-04-08 14:44 ` Vitaly Kuznetsov
2021-04-08 15:52 ` Siddharth Chandrasekaran
2021-04-09 7:38 ` Vitaly Kuznetsov
2021-04-09 7:55 ` Siddharth Chandrasekaran
2021-04-12 8:11 ` Siddharth Chandrasekaran
2021-04-12 11:29 ` Vitaly Kuznetsov
2021-04-08 15:44 ` Wei Liu
2021-04-08 15:56 ` Siddharth Chandrasekaran
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