diff options
Diffstat (limited to 'Documentation/arch/x86')
-rw-r--r-- | Documentation/arch/x86/boot.rst | 10 | ||||
-rw-r--r-- | Documentation/arch/x86/cpuinfo.rst | 69 | ||||
-rw-r--r-- | Documentation/arch/x86/sva.rst | 4 | ||||
-rw-r--r-- | Documentation/arch/x86/usb-legacy-support.rst | 11 |
4 files changed, 39 insertions, 55 deletions
diff --git a/Documentation/arch/x86/boot.rst b/Documentation/arch/x86/boot.rst index 76f53d3450e7..77e6163288db 100644 --- a/Documentation/arch/x86/boot.rst +++ b/Documentation/arch/x86/boot.rst @@ -1038,16 +1038,6 @@ Offset/size: 0x000c/4 This field contains maximal allowed type for setup_data and setup_indirect structs. -The Image Checksum -================== - -From boot protocol version 2.08 onwards the CRC-32 is calculated over -the entire file using the characteristic polynomial 0x04C11DB7 and an -initial remainder of 0xffffffff. The checksum is appended to the -file; therefore the CRC of the file up to the limit specified in the -syssize field of the header is always 0. - - The Kernel Command Line ======================= diff --git a/Documentation/arch/x86/cpuinfo.rst b/Documentation/arch/x86/cpuinfo.rst index 6ef426a52cdc..f80e2a558d2a 100644 --- a/Documentation/arch/x86/cpuinfo.rst +++ b/Documentation/arch/x86/cpuinfo.rst @@ -79,8 +79,9 @@ feature flags. How are feature flags created? ============================== -a: Feature flags can be derived from the contents of CPUID leaves. ------------------------------------------------------------------- +Feature flags can be derived from the contents of CPUID leaves +-------------------------------------------------------------- + These feature definitions are organized mirroring the layout of CPUID leaves and grouped in words with offsets as mapped in enum cpuid_leafs in cpufeatures.h (see arch/x86/include/asm/cpufeatures.h for details). @@ -89,8 +90,9 @@ cpufeatures.h, and if it is detected at run time, the flags will be displayed accordingly in /proc/cpuinfo. For example, the flag "avx2" comes from X86_FEATURE_AVX2 in cpufeatures.h. -b: Flags can be from scattered CPUID-based features. ----------------------------------------------------- +Flags can be from scattered CPUID-based features +------------------------------------------------ + Hardware features enumerated in sparsely populated CPUID leaves get software-defined values. Still, CPUID needs to be queried to determine if a given feature is present. This is done in init_scattered_cpuid_features(). @@ -104,8 +106,9 @@ has only one feature and would waste 31 bits of space in the x86_capability[] array. Since there is a struct cpuinfo_x86 for each possible CPU, the wasted memory is not trivial. -c: Flags can be created synthetically under certain conditions for hardware features. -------------------------------------------------------------------------------------- +Flags can be created synthetically under certain conditions for hardware features +--------------------------------------------------------------------------------- + Examples of conditions include whether certain features are present in MSR_IA32_CORE_CAPS or specific CPU models are identified. If the needed conditions are met, the features are enabled by the set_cpu_cap or @@ -114,8 +117,8 @@ the feature X86_FEATURE_SPLIT_LOCK_DETECT will be enabled and "split_lock_detect" will be displayed. The flag "ring3mwait" will be displayed only when running on INTEL_XEON_PHI_[KNL|KNM] processors. -d: Flags can represent purely software features. ------------------------------------------------- +Flags can represent purely software features +-------------------------------------------- These flags do not represent hardware features. Instead, they represent a software feature implemented in the kernel. For example, Kernel Page Table Isolation is purely software feature and its feature flag X86_FEATURE_PTI is @@ -130,14 +133,18 @@ x86_cap/bug_flags[] arrays in kernel/cpu/capflags.c. The names in the resulting x86_cap/bug_flags[] are used to populate /proc/cpuinfo. The naming of flags in the x86_cap/bug_flags[] are as follows: -a: The name of the flag is from the string in X86_FEATURE_<name> by default. ----------------------------------------------------------------------------- -By default, the flag <name> in /proc/cpuinfo is extracted from the respective -X86_FEATURE_<name> in cpufeatures.h. For example, the flag "avx2" is from -X86_FEATURE_AVX2. +Flags do not appear by default in /proc/cpuinfo +----------------------------------------------- + +Feature flags are omitted by default from /proc/cpuinfo as it does not make +sense for the feature to be exposed to userspace in most cases. For example, +X86_FEATURE_ALWAYS is defined in cpufeatures.h but that flag is an internal +kernel feature used in the alternative runtime patching functionality. So the +flag does not appear in /proc/cpuinfo. + +Specify a flag name if absolutely needed +---------------------------------------- -b: The naming can be overridden. --------------------------------- If the comment on the line for the #define X86_FEATURE_* starts with a double-quote character (""), the string inside the double-quote characters will be the name of the flags. For example, the flag "sse4_1" comes from @@ -148,36 +155,31 @@ needed. For instance, /proc/cpuinfo is a userspace interface and must remain constant. If, for some reason, the naming of X86_FEATURE_<name> changes, one shall override the new naming with the name already used in /proc/cpuinfo. -c: The naming override can be "", which means it will not appear in /proc/cpuinfo. ----------------------------------------------------------------------------------- -The feature shall be omitted from /proc/cpuinfo if it does not make sense for -the feature to be exposed to userspace. For example, X86_FEATURE_ALWAYS is -defined in cpufeatures.h but that flag is an internal kernel feature used -in the alternative runtime patching functionality. So, its name is overridden -with "". Its flag will not appear in /proc/cpuinfo. - Flags are missing when one or more of these happen ================================================== -a: The hardware does not enumerate support for it. --------------------------------------------------- +The hardware does not enumerate support for it +---------------------------------------------- + For example, when a new kernel is running on old hardware or the feature is not enabled by boot firmware. Even if the hardware is new, there might be a problem enabling the feature at run time, the flag will not be displayed. -b: The kernel does not know about the flag. -------------------------------------------- +The kernel does not know about the flag +--------------------------------------- + For example, when an old kernel is running on new hardware. -c: The kernel disabled support for it at compile-time. ------------------------------------------------------- +The kernel disabled support for it at compile-time +-------------------------------------------------- + For example, if 5-level-paging is not enabled when building (i.e., CONFIG_X86_5LEVEL is not selected) the flag "la57" will not show up [#f1]_. Even though the feature will still be detected via CPUID, the kernel disables it by clearing via setup_clear_cpu_cap(X86_FEATURE_LA57). -d: The feature is disabled at boot-time. ----------------------------------------- +The feature is disabled at boot-time +------------------------------------ A feature can be disabled either using a command-line parameter or because it failed to be enabled. The command-line parameter clearcpuid= can be used to disable features using the feature number as defined in @@ -190,8 +192,9 @@ disable specific features. The list of parameters includes, but is not limited to, nofsgsbase, nosgx, noxsave, etc. 5-level paging can also be disabled using "no5lvl". -e: The feature was known to be non-functional. ----------------------------------------------- +The feature was known to be non-functional +------------------------------------------ + The feature was known to be non-functional because a dependency was missing at runtime. For example, AVX flags will not show up if XSAVE feature is disabled since they depend on XSAVE feature. Another example would be broken diff --git a/Documentation/arch/x86/sva.rst b/Documentation/arch/x86/sva.rst index 33cb05005982..6a759984d471 100644 --- a/Documentation/arch/x86/sva.rst +++ b/Documentation/arch/x86/sva.rst @@ -25,7 +25,7 @@ to cache translations for virtual addresses. The IOMMU driver uses the mmu_notifier() support to keep the device TLB cache and the CPU cache in sync. When an ATS lookup fails for a virtual address, the device should use the PRI in order to request the virtual address to be paged into the -CPU page tables. The device must use ATS again in order the fetch the +CPU page tables. The device must use ATS again in order to fetch the translation before use. Shared Hardware Workqueues @@ -216,7 +216,7 @@ submitting work and processing completions. Single Root I/O Virtualization (SR-IOV) focuses on providing independent hardware interfaces for virtualizing hardware. Hence, it's required to be -almost fully functional interface to software supporting the traditional +an almost fully functional interface to software supporting the traditional BARs, space for interrupts via MSI-X, its own register layout. Virtual Functions (VFs) are assisted by the Physical Function (PF) driver. diff --git a/Documentation/arch/x86/usb-legacy-support.rst b/Documentation/arch/x86/usb-legacy-support.rst index e01c08b7c981..b17bf122270a 100644 --- a/Documentation/arch/x86/usb-legacy-support.rst +++ b/Documentation/arch/x86/usb-legacy-support.rst @@ -20,11 +20,7 @@ It has several drawbacks, though: features (wheel, extra buttons, touchpad mode) of the real PS/2 mouse may not be available. -2) If CONFIG_HIGHMEM64G is enabled, the PS/2 mouse emulation can cause - system crashes, because the SMM BIOS is not expecting to be in PAE mode. - The Intel E7505 is a typical machine where this happens. - -3) If AMD64 64-bit mode is enabled, again system crashes often happen, +2) If AMD64 64-bit mode is enabled, again system crashes often happen, because the SMM BIOS isn't expecting the CPU to be in 64-bit mode. The BIOS manufacturers only test with Windows, and Windows doesn't do 64-bit yet. @@ -38,11 +34,6 @@ Problem 1) compiled-in, too. Problem 2) - can currently only be solved by either disabling HIGHMEM64G - in the kernel config or USB Legacy support in the BIOS. A BIOS update - could help, but so far no such update exists. - -Problem 3) is usually fixed by a BIOS update. Check the board manufacturers web site. If an update is not available, disable USB Legacy support in the BIOS. If this alone doesn't help, try also adding |