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From: Richard Henderson <richard.henderson@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>,
	qemu-arm@nongnu.org, qemu-devel@nongnu.org
Subject: Re: [PATCH v2 04/57] target/arm: Add handling for PSR.ECI/ICI
Date: Mon, 14 Jun 2021 12:15:23 -0700	[thread overview]
Message-ID: <ea4f1b0c-4e7a-c900-3bdf-d24bda0b5b29@linaro.org> (raw)
In-Reply-To: <20210614151007.4545-5-peter.maydell@linaro.org>

On 6/14/21 8:09 AM, Peter Maydell wrote:
> On A-profile, PSR bits [15:10][26:25] are always the IT state bits.
> On M-profile, some of the reserved encodings of the IT state are used
> to instead indicate partial progress through instructions that were
> interrupted partway through by an exception and can be resumed.
> 
> These resumable instructions fall into two categories:
> 
> (1) load/store multiple instructions, where these bits are called
> "ICI" and specify the register in the ldm/stm list where execution
> should resume.  (Specifically: LDM, STM, VLDM, VSTM, VLLDM, VLSTM,
> CLRM, VSCCLRM.)
> 
> (2) MVE instructions subject to beatwise execution, where these bits
> are called "ECI" and specify which beats in this and possibly also
> the following MVE insn have been executed.
> 
> There are also a few insns (LE, LETP, and BKPT) which do not use the
> ICI/ECI bits but must leave them alone.
> 
> Otherwise, we should raise an INVSTATE UsageFault for any attempt to
> execute an insn with non-zero ICI/ECI bits.
> 
> So far we have been able to ignore ECI/ICI, because the architecture
> allows the IMPDEF choice of "always restart load/store multiple from
> the beginning regardless of ICI state", so the only thing we have
> been missing is that we don't raise the INVSTATE fault for bad guest
> code.  However, MVE requires that we honour ECI bits and do not
> rexecute beats of an insn that have already been executed.
> 
> Add the support in the decoder for handling ECI/ICI:
>   * identify the ECI/ICI case in the CONDEXEC TB flags
>   * when a load/store multiple insn succeeds, it updates the ECI/ICI
>     state (both in DisasContext and in the CPU state), and sets a flag
>     to say that the ECI/ICI state was handled
>   * if we find that the insn we just decoded did not handle the
>     ECI/ICI state, we delete all the code that we just generated for
>     it and instead emit the code to raise the INVFAULT.  This allows
>     us to avoid having to update every non-MVE non-LDM/STM insn to
>     make it check for "is ECI/ICI set?".
> 
> We continue with our existing IMPDEF choice of not caring about the
> ICI state for the load/store multiples and simply restarting them
> from the beginning.  Because we don't allow interrupts in the middle
> of an insn, the only way we would see this state is if the guest set
> ICI manually on return from an exception handler, so it's a corner
> case which doesn't merit optimisation.
> 
> ICI update for LDM/STM is simple -- it always zeroes the state.  ECI
> update for MVE beatwise insns will be a little more complex, since
> the ECI state may include information for the following insn.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> v1->v2: minor changes as suggested by rth

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~


  reply	other threads:[~2021-06-14 19:17 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-14 15:09 [PATCH v2 00/57] target/arm: First slice of MVE implementation Peter Maydell
2021-06-14 15:09 ` [PATCH v2 01/57] target/arm: Provide and use H8 and H1_8 macros Peter Maydell
2021-06-14 15:09 ` [PATCH v2 02/57] target/arm: Enable FPSCR.QC bit for MVE Peter Maydell
2021-06-14 15:09 ` [PATCH v2 03/57] target/arm: Handle VPR semantics in existing code Peter Maydell
2021-06-14 15:09 ` [PATCH v2 04/57] target/arm: Add handling for PSR.ECI/ICI Peter Maydell
2021-06-14 19:15   ` Richard Henderson [this message]
2021-06-14 15:09 ` [PATCH v2 05/57] target/arm: Let vfp_access_check() handle late NOCP checks Peter Maydell
2021-06-14 15:09 ` [PATCH v2 06/57] target/arm: Implement MVE LCTP Peter Maydell
2021-06-14 15:09 ` [PATCH v2 07/57] target/arm: Implement MVE WLSTP insn Peter Maydell
2021-06-14 19:20   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 08/57] target/arm: Implement MVE DLSTP Peter Maydell
2021-06-14 15:09 ` [PATCH v2 09/57] target/arm: Implement MVE LETP insn Peter Maydell
2021-06-14 15:09 ` [PATCH v2 10/57] target/arm: Add framework for MVE decode Peter Maydell
2021-06-14 15:09 ` [PATCH v2 11/57] target/arm: Implement MVE VLDR/VSTR (non-widening forms) Peter Maydell
2021-06-14 19:29   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 12/57] target/arm: Implement widening/narrowing MVE VLDR/VSTR insns Peter Maydell
2021-06-14 19:39   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 13/57] target/arm: Move expand_pred_b() data to translate.c Peter Maydell
2021-06-14 19:41   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 14/57] target/arm: Implement MVE VCLZ Peter Maydell
2021-06-14 20:00   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 15/57] target/arm: Implement MVE VCLS Peter Maydell
2021-06-14 15:09 ` [PATCH v2 16/57] bitops.h: Provide hswap32(), hswap64(), wswap64() swapping operations Peter Maydell
2021-06-14 15:09 ` [PATCH v2 17/57] target/arm: Implement MVE VREV16, VREV32, VREV64 Peter Maydell
2021-06-14 20:03   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 18/57] target/arm: Implement MVE VMVN (register) Peter Maydell
2021-06-14 15:09 ` [PATCH v2 19/57] target/arm: Implement MVE VABS Peter Maydell
2021-06-14 20:06   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 20/57] target/arm: Implement MVE VNEG Peter Maydell
2021-06-14 15:09 ` [PATCH v2 21/57] tcg: Make gen_dup_i32() public Peter Maydell
2021-06-14 20:12   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 22/57] target/arm: Implement MVE VDUP Peter Maydell
2021-06-14 20:15   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 23/57] target/arm: Implement MVE VAND, VBIC, VORR, VORN, VEOR Peter Maydell
2021-06-14 15:09 ` [PATCH v2 24/57] target/arm: Implement MVE VADD, VSUB, VMUL Peter Maydell
2021-06-14 15:09 ` [PATCH v2 25/57] target/arm: Implement MVE VMULH Peter Maydell
2021-06-14 15:09 ` [PATCH v2 26/57] target/arm: Implement MVE VRMULH Peter Maydell
2021-06-14 15:09 ` [PATCH v2 27/57] target/arm: Implement MVE VMAX, VMIN Peter Maydell
2021-06-14 15:09 ` [PATCH v2 28/57] target/arm: Implement MVE VABD Peter Maydell
2021-06-14 15:09 ` [PATCH v2 29/57] target/arm: Implement MVE VHADD, VHSUB Peter Maydell
2021-06-14 15:09 ` [PATCH v2 30/57] target/arm: Implement MVE VMULL Peter Maydell
2021-06-14 15:09 ` [PATCH v2 31/57] target/arm: Implement MVE VMLALDAV Peter Maydell
2021-06-14 15:09 ` [PATCH v2 32/57] target/arm: Implement MVE VMLSLDAV Peter Maydell
2021-06-14 15:09 ` [PATCH v2 33/57] include/qemu/int128.h: Add function to create Int128 from int64_t Peter Maydell
2021-06-14 15:09 ` [PATCH v2 34/57] target/arm: Implement MVE VRMLALDAVH, VRMLSLDAVH Peter Maydell
2021-06-14 21:27   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 35/57] target/arm: Implement MVE VADD (scalar) Peter Maydell
2021-06-14 21:30   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 36/57] target/arm: Implement MVE VSUB, VMUL (scalar) Peter Maydell
2021-06-14 15:09 ` [PATCH v2 37/57] target/arm: Implement MVE VHADD, VHSUB (scalar) Peter Maydell
2021-06-14 15:09 ` [PATCH v2 38/57] target/arm: Implement MVE VBRSR Peter Maydell
2021-06-14 15:09 ` [PATCH v2 39/57] target/arm: Implement MVE VPST Peter Maydell
2021-06-14 15:09 ` [PATCH v2 40/57] target/arm: Implement MVE VQADD and VQSUB Peter Maydell
2021-06-14 15:09 ` [PATCH v2 41/57] target/arm: Implement MVE VQDMULH and VQRDMULH (scalar) Peter Maydell
2021-06-14 15:09 ` [PATCH v2 42/57] target/arm: Implement MVE VQDMULL scalar Peter Maydell
2021-06-14 15:09 ` [PATCH v2 43/57] target/arm: Implement MVE VQDMULH, VQRDMULH (vector) Peter Maydell
2021-06-14 15:09 ` [PATCH v2 44/57] target/arm: Implement MVE VQADD, VQSUB (vector) Peter Maydell
2021-06-14 15:09 ` [PATCH v2 45/57] target/arm: Implement MVE VQSHL (vector) Peter Maydell
2021-06-14 21:43   ` Richard Henderson
2021-06-14 15:09 ` [PATCH v2 46/57] target/arm: Implement MVE VQRSHL Peter Maydell
2021-06-14 15:09 ` [PATCH v2 47/57] target/arm: Implement MVE VSHL insn Peter Maydell
2021-06-14 15:09 ` [PATCH v2 48/57] target/arm: Implmement MVE VRSHL Peter Maydell
2021-06-14 15:09 ` [PATCH v2 49/57] target/arm: Implement MVE VQDMLADH and VQRDMLADH Peter Maydell
2021-06-14 15:10 ` [PATCH v2 50/57] target/arm: Implement MVE VQDMLSDH and VQRDMLSDH Peter Maydell
2021-06-14 15:10 ` [PATCH v2 51/57] target/arm: Implement MVE VQDMULL (vector) Peter Maydell
2021-06-14 15:10 ` [PATCH v2 52/57] target/arm: Implement MVE VRHADD Peter Maydell
2021-06-14 15:10 ` [PATCH v2 53/57] target/arm: Implement MVE VADC, VSBC Peter Maydell
2021-06-14 21:58   ` Richard Henderson
2021-06-14 15:10 ` [PATCH v2 54/57] target/arm: Implement MVE VCADD Peter Maydell
2021-06-14 15:10 ` [PATCH v2 55/57] target/arm: Implement MVE VHCADD Peter Maydell
2021-06-14 22:01   ` Richard Henderson
2021-06-14 15:10 ` [PATCH v2 56/57] target/arm: Implement MVE VADDV Peter Maydell
2021-06-14 15:10 ` [PATCH v2 57/57] target/arm: Make VMOV scalar <-> gpreg beatwise for MVE Peter Maydell
2021-06-14 22:20 ` [PATCH v2 00/57] target/arm: First slice of MVE implementation no-reply
2021-06-14 22:22 ` Richard Henderson
2021-06-21 16:37   ` Peter Maydell
2021-06-21 17:13     ` Richard Henderson

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