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Tue, 15 Aug 2023 20:19:24 -0700 (PDT) Received: from localhost.localdomain ([146.112.118.69]) by smtp.gmail.com with ESMTPSA id m22-20020aa78a16000000b00686f048bb9dsm122891pfa.74.2023.08.15.20.19.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Aug 2023 20:19:23 -0700 (PDT) Subject: Re: [PATCH v3 4/6] KVM: PPC: Book3s HV: Hold LPIDs in an unsigned long To: David Laight , "linuxppc-dev@lists.ozlabs.org" References: <20230807014553.1168699-1-jniethe5@gmail.com> <20230807014553.1168699-5-jniethe5@gmail.com> <014488c6d90446f38154a2f7645aa053@AcuMS.aculab.com> From: Jordan Niethe Message-ID: <1b187307-596d-392f-45a6-3da2c9aa20d9@gmail.com> Date: Wed, 16 Aug 2023 13:19:17 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <014488c6d90446f38154a2f7645aa053@AcuMS.aculab.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "mikey@neuling.org" , "sbhat@linux.ibm.com" , "kvm@vger.kernel.org" , "amachhiw@linux.vnet.ibm.com" , "gautam@linux.ibm.com" , "npiggin@gmail.com" , "kvm-ppc@vger.kernel.org" , "vaibhav@linux.ibm.com" , "kconsul@linux.vnet.ibm.com" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 14/8/23 6:15 pm, David Laight wrote: > From: Jordan Niethe >> Sent: 07 August 2023 02:46 >> >> The LPID register is 32 bits long. The host keeps the lpids for each >> guest in an unsigned word struct kvm_arch. Currently, LPIDs are already >> limited by mmu_lpid_bits and KVM_MAX_NESTED_GUESTS_SHIFT. >> >> The nestedv2 API returns a 64 bit "Guest ID" to be used be the L1 host >> for each L2 guest. This value is used as an lpid, e.g. it is the >> parameter used by H_RPT_INVALIDATE. To minimize needless special casing >> it makes sense to keep this "Guest ID" in struct kvm_arch::lpid. >> >> This means that struct kvm_arch::lpid is too small so prepare for this >> and make it an unsigned long. This is not a problem for the KVM-HV and >> nestedv1 cases as their lpid values are already limited to valid ranges >> so in those contexts the lpid can be used as an unsigned word safely as >> needed. > > Shouldn't it be changed to u64? This will only be for 64-bit PPC so an unsigned long will always be 64 bits wide, but I can use a u64 instead. > > David > > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) >