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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1726588863; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=s/ofPsoeUxqxDQv2RABQLnVI8pNi50vFOv5/rQ2rWf0=; b=hNAl6iL7OiJ+/MRZ32Ws9QDC4FSSIzpTMhN2vRyxWG1lJ1Zel7s3KVgpLTrYWfOfN2yjtS 0k2oIdu5vSCR7Dh/0G5Sn5m9hIbEEX2wkxg+sZzgY/oquoG2w0O0/ty1eykJcCeHSA6XFI 7IKFm18cQtiZ2m8QoolxMKpEgE1G+2g= X-MC-Unique: lmdaCVsgNu-c0V9JHBsEug-1 From: Vitaly Kuznetsov To: qemu-devel@nongnu.org, Paolo Bonzini Subject: [PATCH RESEND v4 4/4] docs/system: Add recommendations to Hyper-V enlightenments doc Date: Tue, 17 Sep 2024 18:00:51 +0200 Message-ID: <20240917160051.2637594-5-vkuznets@redhat.com> In-Reply-To: <20240917160051.2637594-1-vkuznets@redhat.com> References: <20240917160051.2637594-1-vkuznets@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=vkuznets@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1726589038903116600 Content-Type: text/plain; charset="utf-8" While hyperv.rst already has all currently implemented Hyper-V enlightenments documented, it may be unclear what is the recommended set to achieve the best result. Add the corresponding section to the doc. Signed-off-by: Vitaly Kuznetsov --- docs/system/i386/hyperv.rst | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/docs/system/i386/hyperv.rst b/docs/system/i386/hyperv.rst index 009947e39141..1c1de77feb65 100644 --- a/docs/system/i386/hyperv.rst +++ b/docs/system/i386/hyperv.rst @@ -283,6 +283,36 @@ Supplementary features feature alters this behavior and only allows the guest to use exposed Hy= per-V enlightenments. =20 +Recommendations +--------------- + +To achieve the best performance of Windows and Hyper-V guests and unless t= here +are any specific requirements (e.g. migration to older QEMU/KVM versions, +emulating specific Hyper-V version, ...), it is recommended to enable all +currently implemented Hyper-V enlightenments with the following exceptions: + +- ``hv-syndbg``, ``hv-passthrough``, ``hv-enforce-cpuid`` should not be en= abled + in production configurations as these are debugging/development features. +- ``hv-reset`` can be avoided as modern Hyper-V versions don't expose it. +- ``hv-evmcs`` can (and should) be enabled on Intel CPUs only. While the f= eature + is only used in nested configurations (Hyper-V, WSL2), enabling it for r= egular + Windows guests should not have any negative effects. +- ``hv-no-nonarch-coresharing`` must only be enabled if vCPUs are properly= pinned + so no non-architectural core sharing is possible. +- ``hv-vendor-id``, ``hv-version-id-build``, ``hv-version-id-major``, + ``hv-version-id-minor``, ``hv-version-id-spack``, ``hv-version-id-sbranc= h``, + ``hv-version-id-snumber`` can be left unchanged, guests are not supposed= to + behave differently when different Hyper-V version is presented to them. +- ``hv-crash`` must only be enabled if the crash information is consumed v= ia + QAPI by higher levels of the virtualization stack. Enabling this feature + effectively prevents Windows from creating dumps upon crashes. +- ``hv-reenlightenment`` can only be used on hardware which supports TSC + scaling or when guest migration is not needed. +- ``hv-spinlocks`` should be set to e.g. 0xfff when host CPUs are overcomm= ited + (meaning there are other scheduled tasks or guests) and can be left unch= anged + from the default value (0xffffffff) otherwise. +- ``hv-avic``/``hv-apicv`` should not be enabled if the hardware does not + support APIC virtualization (Intel APICv, AMD AVIC). =20 Useful links ------------ --=20 2.46.0