From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HTML_MESSAGE,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DED12C433ED for ; Wed, 12 May 2021 20:03:58 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4C2C0613F7 for ; Wed, 12 May 2021 20:03:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4C2C0613F7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=eldorado.org.br Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:52608 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lgv5J-000423-0c for qemu-devel@archiver.kernel.org; Wed, 12 May 2021 16:03:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58188) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lguKc-0005Ca-25; Wed, 12 May 2021 15:15:42 -0400 Received: from [201.28.113.2] (port=6624 helo=outlook.eldorado.org.br) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lguKW-0002hY-Rp; Wed, 12 May 2021 15:15:41 -0400 Received: from power9a ([10.10.71.235]) by outlook.eldorado.org.br with Microsoft SMTPSVC(8.5.9600.16384); Wed, 12 May 2021 16:15:33 -0300 Received: from [127.0.0.1] (unknown [10.10.71.235]) by power9a (Postfix) with ESMTPS id B96898000C2; Wed, 12 May 2021 16:15:32 -0300 (-03) Subject: Re: [PATCH 07/11] target/ppc: added KVM fallback to fpscr manipulation To: Richard Henderson , qemu-devel@nongnu.org References: <20210512140813.112884-1-bruno.larsen@eldorado.org.br> <20210512140813.112884-8-bruno.larsen@eldorado.org.br> From: Bruno Piazera Larsen Message-ID: <715dfc12-9873-93fd-afd1-e093ae9fae31@eldorado.org.br> Date: Wed, 12 May 2021 16:15:32 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/alternative; boundary="------------FBA01238F5C51294C5FF6023" Content-Language: en-US X-OriginalArrivalTime: 12 May 2021 19:15:33.0117 (UTC) FILETIME=[2E14D2D0:01D74763] X-Host-Lookup-Failed: Reverse DNS lookup failed for 201.28.113.2 (failed) Received-SPF: pass client-ip=201.28.113.2; envelope-from=bruno.larsen@eldorado.org.br; helo=outlook.eldorado.org.br X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, HTML_MESSAGE=0.001, NICE_REPLY_A=-0.001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: farosas@linux.ibm.com, luis.pires@eldorado.org.br, lucas.araujo@eldorado.org.br, fernando.valle@eldorado.org.br, qemu-ppc@nongnu.org, matheus.ferst@eldorado.org.br, david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is a multi-part message in MIME format. --------------FBA01238F5C51294C5FF6023 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit On 12/05/2021 15:20, Richard Henderson wrote: > On 5/12/21 9:08 AM, Bruno Larsen (billionai) wrote: >> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c >> index 104a308abb..a8a720eb48 100644 >> --- a/target/ppc/kvm.c >> +++ b/target/ppc/kvm.c >> @@ -2947,3 +2947,17 @@ bool kvm_arch_cpu_check_are_resettable(void) >>   { >>       return true; >>   } >> + >> +void kvmppc_store_fpscr(CPUPPCState *env, uint64_t arg, uint32_t mask) >> +{ >> +    CPUState *cs = env_cpu(env); >> +    struct kvm_one_reg reg; >> +    int ret; >> +    reg.id = KVM_REG_PPC_FPSCR; >> +    reg.addr = (uintptr_t) &env->fpscr; >> +    ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, ®); >> +    if (ret < 0) >> +    { >> +        fprintf(stderr, "Unable to set FPSCR to KVM: %s", >> strerror(errno)); >> +    } >> +} > > This is all unnecessary.  All you need to do is store to env->fpscr > and the value will be synced back with kvm_put_fp. I figured this was too complicated again, but didn't have a better idea > > I'll note that some of the trouble you may be having with extracting > helper_store_fpscr to a ppc_store_fpscr function is due to an existing > bug in the tcg code: > > Storing to fpscr should *never* raise an exception -- see MTFSF, > MTFSB0, MTFSB1.  Thus the mucking about with cs->exception_index and > env->error_code is incorrect. > > In addition, the masking is being done weirdly and could use a > complete overhaul. > > This could all be rewritten as > > -- %< -- cpu.h > >  /* Invalid operation exception summary */ > - #define fpscr_ix ((env->fpscr) & ((1 << FPSCR_VXSNAN) ... > + #define FPSCR_IX  ((1 << FPSCR_VXSNAN) | ...) > > -- %< -- cpu.c > > // move fpscr_set_rounding_mode here > > void ppc_store_fpscr(CPUPPCState *env, target_ulong val) > { >     /* Recompute exception summary state. */ >     val &= ~(FP_VX | FP_FEX); >     if (val & FPSCR_IX) { >         val |= FP_VX; >     } >     if ((val >> FPSCR_XX) & (val >> FPSCR_XE) & 0x1f) { >         val |= FP_FEX; >     } >     env->fpscr = val; >     if (tcg_enabled()) { >         fpscr_set_rounding_mode(env); >     } > } > > -- %< -- fpu_helper.c > > void helper_store_fpscr(CPUPPCState *env, target_ulong val, >                         uint32_t nibbles) > { >     target_ulong mask = 0; > >     /* TODO: Push this expansion back to translation time. */ >     for (int i = 0; i < sizeof(target_ulong) * 2; ++i) { >         if (nibbles & (1 << i)) { >             mask |= (target_ulong)0xf << (4 * i); >         } >     } > >     val = (val & mask) | (env->fpscr & ~mask); >     ppc_store_fpscr(env, val); > } > > void helper_fpscr_clrbit(CPUPPCState *env, uint32_t bit) > { >     uint32_t mask = 1u << bit; >     if (env->fpscr & mask) { >         ppc_store_fpscr(env, env->fpscr & ~mask); >     } > } > > void helper_fpscr_setbit(CPUPPCState *env, uint32_t bit) > { >     uint32_t mask = 1u << bit; >     if (!(env->fpscr & mask)) { >         ppc_store_fpscr(env, env->fpscr | mask); >     } > } > > There are a couple of other uses of fpscr_set_rounding_mode, where the > softfloat value is changed temporarily (do_fri, VSX_ROUND). These > should simply save the previous softfloat value (using > get_float_rounding_mode) around the operation instead of re-computing > from fpscr. > > Which leaves us with exactly one use of fpscr_set_rounding_mode, which > can then be moved to cpu.c next to ppc_store_fpscr. > ok, yeah, I can definitely try this. > > r~ -- Bruno Piazera Larsen Instituto de Pesquisas ELDORADO Departamento Computação Embarcada Analista de Software Trainee Aviso Legal - Disclaimer --------------FBA01238F5C51294C5FF6023 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit


On 12/05/2021 15:20, Richard Henderson wrote:
On 5/12/21 9:08 AM, Bruno Larsen (billionai) wrote:
diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
index 104a308abb..a8a720eb48 100644
--- a/target/ppc/kvm.c
+++ b/target/ppc/kvm.c
@@ -2947,3 +2947,17 @@ bool kvm_arch_cpu_check_are_resettable(void)
  {
      return true;
  }
+
+void kvmppc_store_fpscr(CPUPPCState *env, uint64_t arg, uint32_t mask)
+{
+    CPUState *cs = env_cpu(env);
+    struct kvm_one_reg reg;
+    int ret;
+    reg.id = KVM_REG_PPC_FPSCR;
+    reg.addr = (uintptr_t) &env->fpscr;
+    ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
+    if (ret < 0)
+    {
+        fprintf(stderr, "Unable to set FPSCR to KVM: %s", strerror(errno));
+    }
+}

This is all unnecessary.  All you need to do is store to env->fpscr and the value will be synced back with kvm_put_fp.
I figured this was too complicated again, but didn't have a better idea

I'll note that some of the trouble you may be having with extracting helper_store_fpscr to a ppc_store_fpscr function is due to an existing bug in the tcg code:

Storing to fpscr should *never* raise an exception -- see MTFSF, MTFSB0, MTFSB1.  Thus the mucking about with cs->exception_index and env->error_code is incorrect.

In addition, the masking is being done weirdly and could use a complete overhaul.

This could all be rewritten as

-- %< -- cpu.h

 /* Invalid operation exception summary */
- #define fpscr_ix ((env->fpscr) & ((1 << FPSCR_VXSNAN) ...
+ #define FPSCR_IX  ((1 << FPSCR_VXSNAN) | ...)

-- %< -- cpu.c

// move fpscr_set_rounding_mode here

void ppc_store_fpscr(CPUPPCState *env, target_ulong val)
{
    /* Recompute exception summary state. */
    val &= ~(FP_VX | FP_FEX);
    if (val & FPSCR_IX) {
        val |= FP_VX;
    }
    if ((val >> FPSCR_XX) & (val >> FPSCR_XE) & 0x1f) {
        val |= FP_FEX;
    }
    env->fpscr = val;
    if (tcg_enabled()) {
        fpscr_set_rounding_mode(env);
    }
}

-- %< -- fpu_helper.c

void helper_store_fpscr(CPUPPCState *env, target_ulong val,
                        uint32_t nibbles)
{
    target_ulong mask = 0;

    /* TODO: Push this expansion back to translation time. */
    for (int i = 0; i < sizeof(target_ulong) * 2; ++i) {
        if (nibbles & (1 << i)) {
            mask |= (target_ulong)0xf << (4 * i);
        }
    }

    val = (val & mask) | (env->fpscr & ~mask);
    ppc_store_fpscr(env, val);
}

void helper_fpscr_clrbit(CPUPPCState *env, uint32_t bit)
{
    uint32_t mask = 1u << bit;
    if (env->fpscr & mask) {
        ppc_store_fpscr(env, env->fpscr & ~mask);
    }
}

void helper_fpscr_setbit(CPUPPCState *env, uint32_t bit)
{
    uint32_t mask = 1u << bit;
    if (!(env->fpscr & mask)) {
        ppc_store_fpscr(env, env->fpscr | mask);
    }
}

There are a couple of other uses of fpscr_set_rounding_mode, where the softfloat value is changed temporarily (do_fri, VSX_ROUND).  These should simply save the previous softfloat value (using get_float_rounding_mode) around the operation instead of re-computing from fpscr.

Which leaves us with exactly one use of fpscr_set_rounding_mode, which can then be moved to cpu.c next to ppc_store_fpscr.

ok, yeah, I can definitely try this.

r~
--
Bruno Piazera Larsen
Instituto de Pesquisas ELDORADO
Departamento Computação Embarcada
Analista de Software Trainee
Aviso Legal - Disclaimer
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