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a="187974714" X-IronPort-AV: E=Sophos;i="5.82,310,1613462400"; d="scan'208";a="187974714" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 May 2021 16:29:30 -0700 IronPort-SDR: /+e+s9tSYNxtLIFcO43SvAGYdrC/2c0XG7MuFApcWnjObitK+etYirQYkZ+TSKaAHJpU0RHGxC 4xiyzmf9gZZA== X-IronPort-AV: E=Sophos;i="5.82,310,1613462400"; d="scan'208";a="542177421" Received: from craigsmi-mobl.amr.corp.intel.com (HELO [10.212.132.228]) ([10.212.132.228]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 May 2021 16:29:28 -0700 Subject: Re: [RFC v2-fix-v2 1/1] x86/tdx: Wire up KVM hypercalls To: Kuppuswamy Sathyanarayanan , Peter Zijlstra , Andy Lutomirski Cc: Tony Luck , Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Dan Williams , Raj Ashok , Sean Christopherson , linux-kernel@vger.kernel.org References: <36760dae-2f61-2072-460a-f8359224fcf1@intel.com> <20210518211938.635092-1-sathyanarayanan.kuppuswamy@linux.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210518211938.635092-1-sathyanarayanan.kuppuswamy@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/18/21 2:19 PM, Kuppuswamy Sathyanarayanan wrote: > From: "Kirill A. Shutemov" > > KVM hypercalls use the "vmcall" or "vmmcall" instructions. > Although the ABI is similar, those instructions no longer > function for TDX guests. Make vendor-specific TDVMCALLs > instead of VMCALL. This enables TDX guests to run with KVM > acting as the hypervisor. TDX guests running under other > hypervisors will continue to use those hypervisor's > hypercalls. Well, I screwed this up when I typed it too, but it is: TDX guests running under other hypervisors will continue to use those hypervisors' hypercalls. I hate how that reads, but oh well. > Since KVM hypercall functions can be included and called > from kernel modules, export tdx_kvm_hypercall*() functions > to avoid symbol errors No, you're not avoiding errors, you're exporting the symbol so it can be *USED*. The error comes from it not being exported. It also helps to be specific here: Export tdx_kvm_hypercall*() to make the symbols visible to kvm.ko. > [Isaku Yamahata: proposed KVM VENDOR string] > Signed-off-by: Kirill A. Shutemov > Reviewed-by: Andi Kleen > Signed-off-by: Kuppuswamy Sathyanarayanan Reviewed-by: Dave Hansen Also, FWIW, if you did this in the header: +static inline long tdx_kvm_hypercall0(unsigned int nr) +{ + return tdx_kvm_hypercall(nr, 0, 0, 0, 0); +} You could get away with just exporting tdx_kvm_hypercall() instead of 4 symbols. The rest of the code would look the same.