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-rw-r--r--Documentation/arch/x86/boot.rst10
-rw-r--r--Documentation/arch/x86/cpuinfo.rst69
-rw-r--r--Documentation/arch/x86/sva.rst4
-rw-r--r--Documentation/arch/x86/usb-legacy-support.rst11
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