Hi Matthias, Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on kvm/linux-next] [also build test WARNING on v4.17 next-20180615] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/Matthias-Kaehlcke/kvm-x86-mmu-Add-cast-to-negated-bitmasks-in-update_permission_bitmask/20180616-015357 base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next reproduce: # apt-get install sparse make ARCH=x86_64 allmodconfig make C=1 CF=-D__CHECK_ENDIAN__ sparse warnings: (new ones prefixed by >>) include/linux/seq_buf.h:71:16: sparse: expression using sizeof(void) include/linux/seq_buf.h:71:16: sparse: expression using sizeof(void) include/linux/seq_buf.h:71:16: sparse: expression using sizeof(void) include/linux/seq_buf.h:71:16: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:1123:21: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:1123:21: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:1769:37: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:1769:37: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:1770:35: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:1770:35: sparse: expression using sizeof(void) arch/x86/kvm/paging_tmpl.h:788:33: sparse: expression using sizeof(void) arch/x86/kvm/paging_tmpl.h:788:33: sparse: expression using sizeof(void) arch/x86/kvm/paging_tmpl.h:788:33: sparse: expression using sizeof(void) arch/x86/kvm/paging_tmpl.h:788:33: sparse: expression using sizeof(void) arch/x86/kvm/paging_tmpl.h:788:33: sparse: expression using sizeof(void) arch/x86/kvm/paging_tmpl.h:788:33: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:5168:33: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:5168:33: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:5169:31: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:5169:31: sparse: expression using sizeof(void) arch/x86/kvm/mmu.c:5548:24: sparse: expression using sizeof(void) >> arch/x86/kvm/mmu.c:4280:57: sparse: cast truncates bits from constant value >> (ffffff33 becomes 33) >> arch/x86/kvm/mmu.c:4282:56: sparse: cast truncates bits from constant value >> (ffffff0f becomes f) >> arch/x86/kvm/mmu.c:4284:57: sparse: cast truncates bits from constant value >> (ffffff55 becomes 55) vim +4280 arch/x86/kvm/mmu.c 4247 4248 #define BYTE_MASK(access) \ 4249 ((1 & (access) ? 2 : 0) | \ 4250 (2 & (access) ? 4 : 0) | \ 4251 (3 & (access) ? 8 : 0) | \ 4252 (4 & (access) ? 16 : 0) | \ 4253 (5 & (access) ? 32 : 0) | \ 4254 (6 & (access) ? 64 : 0) | \ 4255 (7 & (access) ? 128 : 0)) 4256 4257 4258 static void update_permission_bitmask(struct kvm_vcpu *vcpu, 4259 struct kvm_mmu *mmu, bool ept) 4260 { 4261 unsigned byte; 4262 4263 const u8 x = BYTE_MASK(ACC_EXEC_MASK); 4264 const u8 w = BYTE_MASK(ACC_WRITE_MASK); 4265 const u8 u = BYTE_MASK(ACC_USER_MASK); 4266 4267 bool cr4_smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP) != 0; 4268 bool cr4_smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP) != 0; 4269 bool cr0_wp = is_write_protection(vcpu); 4270 4271 for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) { 4272 unsigned pfec = byte << 1; 4273 4274 /* 4275 * Each "*f" variable has a 1 bit for each UWX value 4276 * that causes a fault with the given PFEC. 4277 */ 4278 4279 /* Faults from writes to non-writable pages */ > 4280 u8 wf = (pfec & PFERR_WRITE_MASK) ? (u8)~w : 0; 4281 /* Faults from user mode accesses to supervisor pages */ > 4282 u8 uf = (pfec & PFERR_USER_MASK) ? (u8)~u : 0; 4283 /* Faults from fetches of non-executable pages*/ > 4284 u8 ff = (pfec & PFERR_FETCH_MASK) ? (u8)~x : 0; 4285 /* Faults from kernel mode fetches of user pages */ 4286 u8 smepf = 0; 4287 /* Faults from kernel mode accesses of user pages */ 4288 u8 smapf = 0; 4289 4290 if (!ept) { 4291 /* Faults from kernel mode accesses to user pages */ 4292 u8 kf = (pfec & PFERR_USER_MASK) ? 0 : u; 4293 4294 /* Not really needed: !nx will cause pte.nx to fault */ 4295 if (!mmu->nx) 4296 ff = 0; 4297 4298 /* Allow supervisor writes if !cr0.wp */ 4299 if (!cr0_wp) 4300 wf = (pfec & PFERR_USER_MASK) ? wf : 0; 4301 4302 /* Disallow supervisor fetches of user code if cr4.smep */ 4303 if (cr4_smep) 4304 smepf = (pfec & PFERR_FETCH_MASK) ? kf : 0; 4305 4306 /* 4307 * SMAP:kernel-mode data accesses from user-mode 4308 * mappings should fault. A fault is considered 4309 * as a SMAP violation if all of the following 4310 * conditions are ture: 4311 * - X86_CR4_SMAP is set in CR4 4312 * - A user page is accessed 4313 * - The access is not a fetch 4314 * - Page fault in kernel mode 4315 * - if CPL = 3 or X86_EFLAGS_AC is clear 4316 * 4317 * Here, we cover the first three conditions. 4318 * The fourth is computed dynamically in permission_fault(); 4319 * PFERR_RSVD_MASK bit will be set in PFEC if the access is 4320 * *not* subject to SMAP restrictions. 4321 */ 4322 if (cr4_smap) 4323 smapf = (pfec & (PFERR_RSVD_MASK|PFERR_FETCH_MASK)) ? 0 : kf; 4324 } 4325 4326 mmu->permissions[byte] = ff | uf | wf | smepf | smapf; 4327 } 4328 } 4329 --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
