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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id da9sm270504edb.13.2020.11.30.03.03.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Nov 2020 03:03:31 -0800 (PST) Subject: Re: [PATCH RFC 01/39] KVM: x86: fix Xen hypercall page msr handling To: David Woodhouse , Sean Christopherson , Joao Martins Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Ankur Arora , Boris Ostrovsky , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org References: <20190220201609.28290-1-joao.m.martins@oracle.com> <20190220201609.28290-2-joao.m.martins@oracle.com> <20190222013008.GG7224@linux.intel.com> <44b102eb-ea74-7f19-3f4a-41dfc298d372@redhat.com> <188a300f8314dd30a3a71857f63f144a3ce69950.camel@infradead.org> From: Paolo Bonzini Message-ID: <51b7771a-0b76-37e3-a80b-e372a7467aca@redhat.com> Date: Mon, 30 Nov 2020 12:03:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <188a300f8314dd30a3a71857f63f144a3ce69950.camel@infradead.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/11/20 11:39, David Woodhouse wrote: > ... except that's a bit icky because that trick of falling through to > the default case only works for *one* case statement. And more to the > point, the closest thing I can find to a 'kvm_hyperv_enabled()' flag is > what we do for setting the HV_X64_MSR_HYPERCALL_ENABLE flag... which is > based on whether the hv_guest_os_id is set, which in turn is done by > writing one of these MSRs You can use CPUID too (search for Hv#1 in leaf 0x40000000)? Paolo > I suppose we could disable them just by letting Xen take precedence, if > kvm->arch.xen_hvm_config.msr == HV_X64_MSR_GUEST_OS_ID. But that's > basically what Joao's patch already does. It doesn't disable the > *other* Hyper-V MSRs except for the one Xen 'conflicts' with, but I > don't think that matters.