* Ard Biesheuvel [170805 13:54]:
> This replaces a couple of open coded calculations to obtain the
> physical address of a far symbol with calls to the new adr_l etc
> macros.
I gave this series a quick test and omap3 no longer boots it seems.
Regards,
Tony
Hi James,
On Fri, Jul 28, 2017 at 03:10:09PM +0100, James Morse wrote:
> @@ -520,9 +514,16 @@ el1_preempt:
> el0_sync:
> kernel_entry 0
> mrs x25, esr_el1// read the syndrome register
> + mrs x26, far_el1
Just checking, since we are going to access
On Tue, Aug 08, 2017 at 05:48:29PM +0100, James Morse wrote:
> Hi Christoffer,
>
> On 06/06/17 20:59, Christoffer Dall wrote:
> > On Mon, May 15, 2017 at 06:43:49PM +0100, James Morse wrote:
> >> KVM uses tpidr_el2 as its private vcpu register, which makes sense for
> >> non-vhe world switch as
The SVE architecture adds some system registers, ID register fields
and a dedicated ESR exception class.
This patch adds the appropriate definitions that will be needed by
the kernel.
Signed-off-by: Dave Martin
---
arch/arm64/include/asm/esr.h | 3 ++-
This series implements Linux kernel support for the ARM Scalable Vector
Extension (SVE). [1] It supersedes the previous RFC: see [6] for link
and a summary of changes.
This series depends on some series that are headed for v4.14:
see [3], [4], [5].
To reduce spam, some people may not been
The existing FPSIMD context switch code contains a couple of
instances of {set,clear}_ti_thread(task_thread_info(task)). Since
there are thread flag manipulators that operate directly on
task_struct, this verbosity isn't strictly needed.
For consistency, this patch simplifies the affected calls.
Currently, armv8_deprected.c takes charge of the "abi" sysctl
directory, which makes life difficult for other code that wants to
register sysctls in the same directory.
There is a "new" [1] sysctl registration interface that removes the
need to define ctl_tables for parent directories explicitly,
Currently, a guest kernel sees the true CPU feature registers
(ID_*_EL1) when it reads them using MRS instructions. This means
that the guest will observe features that are present in the
hardware but the host doesn't understand or doesn't provide support
for. A guest may legimitately try to use
Currently the regset API doesn't allow for the possibility that
regsets (or at least, the amount of meaningful data in a regset)
may change in size.
In particular, this results in useless padding being added to
coredumps in a regset's current size is smaller than its
theoretical maximum size.
Manipulating the SVE architectural state, including the vector and
predicate registers, first-fault register and the vector length,
requires the use of dedicated instructions added by SVE.
This patch adds suitable assembly functions for saving and
restoring the SVE registers and querying the
This patch adds CONFIG_ARM64_SVE to control building of SVE support
into the kernel, and adds a stub predicate system_supports_sve() to
control conditional compilation and runtime SVE support.
system_supports_sve() just returns false for now: it will be
replaced with a non-trivial implementation
This patch adds the core support for switching and managing the SVE
architectural state of user tasks.
Calls to the existing FPSIMD low-level save/restore functions are
factored out as new functions task_fpsimd_{save,load}(), since SVE
now dynamically may or may not need to be handled at these
This patch defines the representation that will be used for the SVE
register state in the signal frame, and implements support for
saving and restoring the SVE registers around signals.
The same layout will also be used for the in-kernel task state.
Due to the variability of the SVE vector
To enable the kernel to use SVE, all SVE traps from EL1 must be
disabled. To take maximum advantage of the hardware, the full
available vector length also needs to be enabled for EL1 by
programming ZCR_EL2.LEN. (The kernel will program ZCR_EL1.LEN as
required, but this cannot override the limit
It's desirable to be able to reset the vector length to some sane
default for new processes, since the new binary and its libraries
processes may or may not be SVE-aware.
This patch tracks the desired post-exec vector length (if any) in a
new thread member sve_vl_onexec, and adds a new thread
This patch implements the core logic for changing a task's vector
length on request from userspace. This will be used by the ptrace
and prctl frontends that are implemented in later patches.
The SVE architecture permits, but does not require, implementations
to support vector lengths that are
This patch implements support for saving and restoring the SVE
registers around signals.
A fixed-size header struct sve_context is always included in the
signal frame encoding the thread's vector length at the time of
signal delivery, optionally followed by a variable-layout structure
encoding
This patch uses the cpufeatures framework to determine common SVE
capabilities and vector lengths, and configures the runtime SVE
support code appropriately.
ZCR_ELx is not really a feature register, but it is convenient to
use it as a template for recording the maximum vector length
supported by
Kernel-mode NEON will corrupt the SVE vector registers, due to the
way they alias the FPSIMD vector registers in the hardware.
This patch ensures that any live SVE register content for the task
is saved by kernel_neon_begin(). The data will be restored in the
usual way on return to userspace.
This patch adds two arm64-specific prctls, to permit userspace to
control its vector length:
* PR_SVE_SET_VL: set the thread's SVE vector length and vector
length inheritance mode.
* PR_SVE_GET_VL: get the same information.
Although these calls shadow instruction set features in the SVE
This patch defines and implements a new regset NT_ARM_SVE, which
describes a thread's SVE register state. This allows a debugger to
manipulate the SVE state, as well as being included in ELF
coredumps for post-mortem debugging.
Because the regset size and layout are dependent on the thread's
KVM guests cannot currently use SVE, because SVE is always
configured to trap to EL2.
However, a guest that sees SVE reported as present in
ID_AA64PFR0_EL1 may legitimately expect that SVE works and try to
use it. Instead of working, the guest will receive an injected
undef exception, which may
This patch enables detection of hardware SVE support via the
cpufeatures framework, and reports its presence to the kernel and
userspace via the new ARM64_SVE cpucap and HWCAP_SVE hwcap
respectively.
Userspace can also detect SVE using ID_AA64PFR0_EL1, using the
cpufeatures MRS emulation.
When
Stateful CPU architecture extensions may require the signal frame
to grow to a size that exceeds the arch's MINSIGSTKSZ #define.
However, changing this #define is an ABI break.
To allow userspace the option of determining the signal frame size
in a more forwards-compatible way, this patch adds a
This patch adds basic documentation of the user/kernel interface
provided by the for SVE.
Signed-off-by: Dave Martin
---
Documentation/arm64/sve.txt | 454
1 file changed, 454 insertions(+)
create mode 100644
Because of the effect of SVE on the size of the signal frame, the
default vector length used for new processes involves a tradeoff
between performance of SVE-enabled software on the one hand, and
reliability of non-SVE-aware software on the other hand.
For this reason, the best choice depends on
Until KVM has full SVE support, guests must not be allowed to
execute SVE instructions.
This patch enables the necessary traps, and also ensures that the
traps are disabled again on exit from the guest so that the host
can still use SVE if it wants to.
Signed-off-by: Dave Martin
The EFI runtime services ABI allows EFI to make free use of the
FPSIMD registers during EFI runtime service calls, subject to the
callee-save requirements of the AArch64 procedure call standard.
However, the SVE architecture allows upper bits of the SVE vector
registers to be zeroed as a
When trapping forbidden attempts by a guest to use SVE, we want the
guest to see a trap consistent with SVE not being implemented.
This patch injects an undefined instruction exception into the
guest in response to such an exception.
Signed-off-by: Dave Martin
---
The SVE context block in the signal frame needs to be considered
too when computing the maximum possible signal frame size.
Because the size of this block depends on the vector length, this
patch computes the size based not on the thread's current vector
length but instead on the maximum possible
On 9 August 2017 at 20:05, Tony Lindgren wrote:
> * Ard Biesheuvel [170805 13:54]:
>> This replaces a couple of open coded calculations to obtain the
>> physical address of a far symbol with calls to the new adr_l etc
>> macros.
>
> I gave this series
* Ard Biesheuvel [170809 12:24]:
> On 9 August 2017 at 20:05, Tony Lindgren wrote:
> > * Ard Biesheuvel [170805 13:54]:
> >> This replaces a couple of open coded calculations to obtain the
> >> physical address of a far
Hello,
I have a general question on the ptimer test for KVM unit tests for the
ARM/ARM64 platform, as the guest is only allowed to access to the
physical counter and access to the physical timer is not allowed for the
guest (CNTHCTL.EL1PCTEN is set and CNTHCTL.EL1PCEN is clear), so how is
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