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[79.242.60.59]) by smtp.gmail.com with ESMTPSA id t11sm1548498wrz.65.2021.09.29.02.03.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Sep 2021 02:03:10 -0700 (PDT) Subject: Re: [PATCH v1 2/8] x86/xen: simplify xen_oldmem_pfn_is_ram() From: David Hildenbrand To: Boris Ostrovsky , linux-kernel@vger.kernel.org Cc: Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Juergen Gross , Stefano Stabellini , "Michael S. Tsirkin" , Jason Wang , Dave Young , Baoquan He , Vivek Goyal , Michal Hocko , Oscar Salvador , Mike Rapoport , "Rafael J. Wysocki" , x86@kernel.org, xen-devel@lists.xenproject.org, virtualization@lists.linux-foundation.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org References: <20210928182258.12451-1-david@redhat.com> <20210928182258.12451-3-david@redhat.com> <4ab2f8c2-c3d5-30b3-a670-a8b38e218b6e@oracle.com> Organization: Red Hat Message-ID: Date: Wed, 29 Sep 2021 11:03:09 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29.09.21 10:45, David Hildenbrand wrote: >> >> How about >> >>     return a.mem_type != HVMMEM_mmio_dm; >> > > Ha, how could I have missed that :) > >> >> Result should be promoted to int and this has added benefit of not requiring changes in patch 4. >> > > Can we go one step further and do > > > @@ -20,24 +20,11 @@ static int xen_oldmem_pfn_is_ram(unsigned long pfn) > struct xen_hvm_get_mem_type a = { > .domid = DOMID_SELF, > .pfn = pfn, > + .mem_type = HVMMEM_ram_rw, > }; > - int ram; > > - if (HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a)) > - return -ENXIO; > - > - switch (a.mem_type) { > - case HVMMEM_mmio_dm: > - ram = 0; > - break; > - case HVMMEM_ram_rw: > - case HVMMEM_ram_ro: > - default: > - ram = 1; > - break; > - } > - > - return ram; > + HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a); > + return a.mem_type != HVMMEM_mmio_dm; > } > #endif > > > Assuming that if HYPERVISOR_hvm_op() fails that > .mem_type is not set to HVMMEM_mmio_dm. > Okay we can't, due to "__must_check" ... -- Thanks, David / dhildenb