The M-profile architecture floating point system supports
lazy FP state preservation, where FP registers are not
pushed to the stack when an exception occurs but are instead
only saved if and when the first FP instruction in the exception
handler is executed. Implement this in QEMU, corresponding
to the check of LSPACT in the pseudocode ExecuteFPCheck().
Backports commit e33cf0f8d8c9998a7616684f9d6aa0d181b88803 from qemu
Pushing registers to the stack for v7M needs to handle three cases:
* the "normal" case where we pend exceptions
* an "ignore faults" case where we set FSR bits but
do not pend exceptions (this is used when we are
handling some kinds of derived exception on exception entry)
* a "lazy FP stacking" case, where different FSR bits
are set and the exception is pended differently
Implement this by changing the existing flag argument that
tells us whether to ignore faults or not into an enum that
specifies which of the 3 modes we should handle.
Backports commit a356dacf647506bccdf8ecd23574246a8bf615ac from qemu
In the v7M architecture, if an exception is generated in the process
of doing the lazy stacking of FP registers, the handling of
possible escalation to HardFault is treated differently to the normal
approach: it works based on the saved information about exception
readiness that was stored in the FPCCR when the stack frame was
created. Provide a new function armv7m_nvic_set_pending_lazyfp()
which pends exceptions during lazy stacking, and implements
this logic.
This corresponds to the pseudocode TakePreserveFPException().
Backports the relevant parts of commit
a99ba8ab1601904e0fa20325192fc850362ce80e from qemu
Add a new helper function which returns the MMU index to use
for v7M, where the caller specifies all of the security
state, privilege level and whether the execution priority
is negative, and reimplement the existing
arm_v7m_mmu_idx_for_secstate_and_priv() in terms of it.
We are going to need this for the lazy-FP-stacking code.
Backports commit fa6252a988dbe440cd6087bf93cbe0887f0c401b from qemu
The M-profile FPCCR.ASPEN bit indicates that automatic floating-point
context preservation is enabled. Before executing any floating-point
instruction, if FPCCR.ASPEN is set and the CONTROL FPCA/SFPA bits
indicate that there is no active floating point context then we
must create a new context (by initializing FPSCR and setting
FPCA/SFPA to indicate that the context is now active). In the
pseudocode this is handled by ExecuteFPCheck().
Implement this with a new TB flag which tracks whether we
need to create a new FP context.
Backports commit 6000531e19964756673a5f4b694a649ef883605a from qemu
The M-profile FPCCR.S bit indicates the security status of
the floating point context. In the pseudocode ExecuteFPCheck()
function it is unconditionally set to match the current
security state whenever a floating point instruction is
executed.
Implement this by adding a new TB flag which tracks whether
FPCCR.S is different from the current security state, so
that we only need to emit the code to update it in the
less-common case when it is not already set correctly.
Note that we will add the handling for the other work done
by ExecuteFPCheck() in later commits.
Backports commit 6d60c67a1a03be32c3342aff6604cdc5095088d1 from qemu
We are close to running out of TB flags for AArch32; we could
start using the cs_base word, but before we do that we can
economise on our usage by sharing the same bits for the VFP
VECSTRIDE field and the XScale XSCALE_CPAR field. This
works because no XScale CPU ever had VFP.
Backports commit ea7ac69d124c94c6e5579145e727adec9ccbefef from qemu
Move the NS TBFLAG down from bit 19 to bit 6, which has not
been used since commit c1e3781090b9d36c60 in 2015, when we
started passing the entire MMU index in the TB flags rather
than just a 'privilege level' bit.
This rearrangement is not strictly necessary, but means that
we can put M-profile-only bits next to each other rather
than scattered across the flag word.
Backports commit 7fbb535f7aeb22896fedfcf18a1eeff48165f1d7 from qemu
Handle floating point registers in exception return.
This corresponds to pseudocode functions ValidateExceptionReturn(),
ExceptionReturn(), PopStack() and ConsumeExcStackFrame().
Backports commit 6808c4d2d2826920087533f517472c09edc7b0d2 from qemu
The magic value pushed onto the callee stack as an integrity
check is different if floating point is present.
Backports commit 0dc51d66fcfcc4c72011cdafb401fd876ca216e7 from qemu
The TailChain() pseudocode specifies that a tail chaining
exception should sanitize the excReturn all-ones bits and
(if there is no FPU) the excReturn FType bits; we weren't
doing this.
Backports commit 60fba59a2f9a092a44b688df5d058cdd6dd9c276 from qemu
For v8M floating point support, transitions from Secure
to Non-secure state via BLNS and BLXNS must clear the
CONTROL.SFPA bit. (This corresponds to the pseudocode
BranchToNS() function.)
Backports commit 3cd6726f0ba7cc77342ee721bd86094e13b2a42a from qemu
Implement the code which updates the FPCCR register on an
exception entry where we are going to use lazy FP stacking.
We have to defer to the NVIC to determine whether the
various exceptions are currently ready or not.
Backports commit b593c2b81287040ab6f452afec6281e2f7ee487b from qemu
Handle floating point registers in exception entry.
This corresponds to the FP-specific parts of the pseudocode
functions ActivateException() and PushStack().
We defer the code corresponding to UpdateFPCCR() to a later patch.
Backports commit 0ed377a8013f40653a83f6ad2c9693897522d7dc from qemu
Currently the code in v7m_push_stack() which detects a violation
of the v8M stack limit simply returns early if it does so. This
is OK for the current integer-only code, but won't work for the
floating point handling we're about to add. We need to continue
executing the rest of the function so that we check for other
exceptions like not having permission to use the FPU and so
that we correctly set the FPCCR state if we are doing lazy
stacking. Refactor to avoid the early return.
Backports commit 3432c79a4e7345818d2defcf9e61a1bcb2907f9f from qemu
The M-profile CONTROL register has two bits -- SFPA and FPCA --
which relate to floating-point support, and should be RES0 otherwise.
Handle them correctly in the MSR/MRS register access code.
Neither is banked between security states, so they are stored
in v7m.control[M_REG_S] regardless of current security state.
Backports commit 2e1c5bcd32014c9ede1b604ae6c2c653de17fc53 from qemu
If the floating point extension is present, then the SG instruction
must clear the CONTROL_S.SFPA bit. Implement this.
(On a no-FPU system the bit will always be zero, so we don't need
to make the clearing of the bit conditional on ARM_FEATURE_VFP.)
Backports commit 1702071302934af77a072b7ee7c5eadc45b37573 from qemu
Correct the decode of the M-profile "coprocessor and
floating-point instructions" space:
* op0 == 0b11 is always unallocated
* if the CPU has an FPU then all insns with op1 == 0b101
are floating point and go to disas_vfp_insn()
For the moment we leave VLLDM and VLSTM as NOPs; in
a later commit we will fill in the proper implementation
for the case where an FPU is present.
Backports commit 8859ba3c9625e7ceb5599f457a344bcd7c5e112b from qemu
Like AArch64, M-profile floating point has no FPEXC enable
bit to gate floating point; so always set the VFPEN TB flag.
M-profile also has CPACR and NSACR similar to A-profile;
they behave slightly differently:
* the CPACR is banked between Secure and Non-Secure
* if the NSACR forces a trap then this is taken to
the Secure state, not the Non-Secure state
Honour the CPACR and NSACR settings. The NSACR handling
requires us to borrow the exception.target_el field
(usually meaningless for M profile) to distinguish the
NOCP UsageFault taken to Secure state from the more
usual fault taken to the current security state.
Backports commit d87513c0abcbcd856f8e1dee2f2d18903b2c3ea2 from qemu
The only "system register" that M-profile floating point exposes
via the VMRS/VMRS instructions is FPSCR, and it does not have
the odd special case for rd==15. Add a check to ensure we only
expose FPSCR.
Backports commit ef9aae2522c22c05df17dd898099dd5c3f20d688 from qemu
The M-profile floating point support has three associated config
registers: FPCAR, FPCCR and FPDSCR. It also makes the registers
CPACR and NSACR have behaviour other than reads-as-zero.
Add support for all of these as simple reads-as-written registers.
We will hook up actual functionality later.
The main complexity here is handling the FPCCR register, which
has a mix of banked and unbanked bits.
Note that we don't share storage with the A-profile
cpu->cp15.nsacr and cpu->cp15.cpacr_el1, though the behaviour
is quite similar, for two reasons:
* the M profile CPACR is banked between security states
* it preserves the invariant that M profile uses no state
inside the cp15 substruct
Backports commit d33abe82c7c9847284a23e575e1078cccab540b5 from qemu
Enforce that for M-profile various FPSCR bits which are RES0 there
but have defined meanings on A-profile are never settable. This
ensures that M-profile code can't enable the A-profile behaviour
(notably vector length/stride handling) by accident.
Backports commit 5bcf8ed9401e62c73158ba110864ee1375558bf7 from qemu
This change adapts io_readx() to its input access_type. Currently
io_readx() treats any memory access as a read, although it has an
input argument "MMUAccessType access_type". This results in:
1) Calling the tlb_fill() only with MMU_DATA_LOAD
2) Considering only entry->addr_read as the tlb_addr
Buglink: https://bugs.launchpad.net/qemu/+bug/1825359
Backports commit ef5dae6805cce7b59d129d801bdc5db71bcbd60d from qemu
This will not necessarily restrict the size of the TB, since for v7
the majority of constant pool usage is for calls from the out-of-line
ldst code, which is already at the end of the TB. But this does
allow us to save one insn per reference on the off-chance.
Backports commit b4b82d7e9caff7ccca5c621817b5a4b8e95eb9b1 from qemu
There is no point in coding for a 2GB offset when the max TB size
is already limited to 64k. If we further restrict to 32k then we
can eliminate the extra ADDIS instruction.
Backports commit a7cdaf710f2aaaf0be855a338dd67463d4bb99e2 from qemu
If the TB generates too much code, such that backend relocations
overflow, try again with a smaller TB. In support of this, move
relocation processing from a random place within tcg_out_op, in
the handling of branch opcodes, to a new function at the end of
tcg_gen_code.
This is not a complete solution, as there are additional relocs
generated for out-of-line ldst handling and constant pools.
Backports commit 7ecd02a06f8f4c0bbf872ecc15e37035b7e1df5f from qemu
If a TB generates too much code, try again with fewer insns.
Fixes: https://bugs.launchpad.net/bugs/1824853
Backports commit 6e6c4efed995d9eca6ae0cfdb2252df830262f50 from qemu
In order to handle TB's that translate to too much code, we
need to place the control of the length of the translation
in the hands of the code gen master loop.
Backports commit 8b86d6d25807e13a63ab6ea879f976b9f18cc45a from qemu
Will be helpful for s390x. Input 128 bit and output 64 bit only,
which is sufficient for now.
Backports commit 2089fcc9e7b4174d1c351eaa7d277c02188a6dd2 from qemu
Add a new base CPU model called 'Dhyana' to model processors from Hygon
Dhyana(family 18h), which derived from AMD EPYC(family 17h).
The following features bits have been removed compare to AMD EPYC:
aes, pclmulqdq, sha_ni
The Hygon Dhyana support to KVM in Linux is already accepted upstream[1].
So add Hygon Dhyana support to Qemu is necessary to create Hygon's own
CPU model.
Reference:
[1] https://git.kernel.org/tip/fec98069fb72fb656304a3e52265e0c2fc9adf87
Backports commit 8d031cec366f26669807eb43f61eb335973b7053 from qemu
