Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210727055450.2742868-1-anup.patel@wdc.com> <20210727055450.2742868-14-anup.patel@wdc.com>
 <CABvJ_xgyn0yeYnbqN=xA60xmuWL6vwFtLt_b60BF_tnfd8r5cQ@mail.gmail.com> <CAAhSdy2zY+f1FE4hBKmvRL+ShmVfw=RwpLciG7=XhCzoOkU1hw@mail.gmail.com>
In-Reply-To: <CAAhSdy2zY+f1FE4hBKmvRL+ShmVfw=RwpLciG7=XhCzoOkU1hw@mail.gmail.com>
From:   Vincent Chen <vincent.chen@sifive.com>
Date:   Mon, 13 Sep 2021 15:11:18 +0800
Message-ID: <CABvJ_xiWU9d7QqbcbLUXh_3_LM9oc8A=GCD1j__v9DOUBj=arw@mail.gmail.com>
Subject: Re: [PATCH v19 13/17] RISC-V: KVM: FP lazy save/restore
To:     Anup Patel <anup@brainfault.org>
Cc:     Anup Patel <anup.patel@wdc.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Palmer Dabbelt <palmerdabbelt@google.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Alexander Graf <graf@amazon.com>,
        Atish Patra <atish.patra@wdc.com>,
        Alistair Francis <Alistair.Francis@wdc.com>,
        Damien Le Moal <damien.lemoal@wdc.com>,
        KVM General <kvm@vger.kernel.org>,
        kvm-riscv@lists.infradead.org,
        linux-riscv <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Sep 13, 2021 at 1:04 PM Anup Patel <anup@brainfault.org> wrote:
>
> On Mon, Sep 13, 2021 at 10:01 AM Vincent Chen <vincent.chen@sifive.com> wrote:
> >
> > On Tue, Jul 27, 2021 at 3:30 PM Anup Patel <anup.patel@wdc.com> wrote:
> > >
> > > From: Atish Patra <atish.patra@wdc.com>
> > >
> > > This patch adds floating point (F and D extension) context save/restore
> > > for guest VCPUs. The FP context is saved and restored lazily only when
> > > kernel enter/exits the in-kernel run loop and not during the KVM world
> > > switch. This way FP save/restore has minimal impact on KVM performance.
> > >
> > > Signed-off-by: Atish Patra <atish.patra@wdc.com>
> > > Signed-off-by: Anup Patel <anup.patel@wdc.com>
> > > Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> > > Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> > > Reviewed-by: Alexander Graf <graf@amazon.com>
> > > ---
> > >  arch/riscv/include/asm/kvm_host.h |   5 +
> > >  arch/riscv/kernel/asm-offsets.c   |  72 +++++++++++++
> > >  arch/riscv/kvm/vcpu.c             |  91 ++++++++++++++++
> > >  arch/riscv/kvm/vcpu_switch.S      | 174 ++++++++++++++++++++++++++++++
> > >  4 files changed, 342 insertions(+)
> > >
> > > diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> > > index 18b4ec1b5105..99b43229fe7a 100644
> > > --- a/arch/riscv/include/asm/kvm_host.h
> > > +++ b/arch/riscv/include/asm/kvm_host.h
> > > @@ -125,6 +125,7 @@ struct kvm_cpu_context {
> > >         unsigned long sepc;
> > >         unsigned long sstatus;
> > >         unsigned long hstatus;
> > > +       union __riscv_fp_state fp;
> > >  };
> > >
> > >  struct kvm_vcpu_csr {
> > > @@ -239,6 +240,10 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
> > >                         struct kvm_cpu_trap *trap);
> > >
> > >  void __kvm_riscv_switch_to(struct kvm_vcpu_arch *vcpu_arch);
> > > +void __kvm_riscv_fp_f_save(struct kvm_cpu_context *context);
> > > +void __kvm_riscv_fp_f_restore(struct kvm_cpu_context *context);
> > > +void __kvm_riscv_fp_d_save(struct kvm_cpu_context *context);
> > > +void __kvm_riscv_fp_d_restore(struct kvm_cpu_context *context);
> > >
> > >  int kvm_riscv_vcpu_set_interrupt(struct kvm_vcpu *vcpu, unsigned int irq);
> > >  int kvm_riscv_vcpu_unset_interrupt(struct kvm_vcpu *vcpu, unsigned int irq);
> > > diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
> > > index 91c77555d914..24d3827e4837 100644
> > > --- a/arch/riscv/kernel/asm-offsets.c
> > > +++ b/arch/riscv/kernel/asm-offsets.c
> > > @@ -195,6 +195,78 @@ void asm_offsets(void)
> > >         OFFSET(KVM_ARCH_TRAP_HTVAL, kvm_cpu_trap, htval);
> > >         OFFSET(KVM_ARCH_TRAP_HTINST, kvm_cpu_trap, htinst);
> > >
> > > +       /* F extension */
> > > +
> > > +       OFFSET(KVM_ARCH_FP_F_F0, kvm_cpu_context, fp.f.f[0]);
> > > +       OFFSET(KVM_ARCH_FP_F_F1, kvm_cpu_context, fp.f.f[1]);
> > > +       OFFSET(KVM_ARCH_FP_F_F2, kvm_cpu_context, fp.f.f[2]);
> > > +       OFFSET(KVM_ARCH_FP_F_F3, kvm_cpu_context, fp.f.f[3]);
> > > +       OFFSET(KVM_ARCH_FP_F_F4, kvm_cpu_context, fp.f.f[4]);
> > > +       OFFSET(KVM_ARCH_FP_F_F5, kvm_cpu_context, fp.f.f[5]);
> > > +       OFFSET(KVM_ARCH_FP_F_F6, kvm_cpu_context, fp.f.f[6]);
> > > +       OFFSET(KVM_ARCH_FP_F_F7, kvm_cpu_context, fp.f.f[7]);
> > > +       OFFSET(KVM_ARCH_FP_F_F8, kvm_cpu_context, fp.f.f[8]);
> > > +       OFFSET(KVM_ARCH_FP_F_F9, kvm_cpu_context, fp.f.f[9]);
> > > +       OFFSET(KVM_ARCH_FP_F_F10, kvm_cpu_context, fp.f.f[10]);
> > > +       OFFSET(KVM_ARCH_FP_F_F11, kvm_cpu_context, fp.f.f[11]);
> > > +       OFFSET(KVM_ARCH_FP_F_F12, kvm_cpu_context, fp.f.f[12]);
> > > +       OFFSET(KVM_ARCH_FP_F_F13, kvm_cpu_context, fp.f.f[13]);
> > > +       OFFSET(KVM_ARCH_FP_F_F14, kvm_cpu_context, fp.f.f[14]);
> > > +       OFFSET(KVM_ARCH_FP_F_F15, kvm_cpu_context, fp.f.f[15]);
> > > +       OFFSET(KVM_ARCH_FP_F_F16, kvm_cpu_context, fp.f.f[16]);
> > > +       OFFSET(KVM_ARCH_FP_F_F17, kvm_cpu_context, fp.f.f[17]);
> > > +       OFFSET(KVM_ARCH_FP_F_F18, kvm_cpu_context, fp.f.f[18]);
> > > +       OFFSET(KVM_ARCH_FP_F_F19, kvm_cpu_context, fp.f.f[19]);
> > > +       OFFSET(KVM_ARCH_FP_F_F20, kvm_cpu_context, fp.f.f[20]);
> > > +       OFFSET(KVM_ARCH_FP_F_F21, kvm_cpu_context, fp.f.f[21]);
> > > +       OFFSET(KVM_ARCH_FP_F_F22, kvm_cpu_context, fp.f.f[22]);
> > > +       OFFSET(KVM_ARCH_FP_F_F23, kvm_cpu_context, fp.f.f[23]);
> > > +       OFFSET(KVM_ARCH_FP_F_F24, kvm_cpu_context, fp.f.f[24]);
> > > +       OFFSET(KVM_ARCH_FP_F_F25, kvm_cpu_context, fp.f.f[25]);
> > > +       OFFSET(KVM_ARCH_FP_F_F26, kvm_cpu_context, fp.f.f[26]);
> > > +       OFFSET(KVM_ARCH_FP_F_F27, kvm_cpu_context, fp.f.f[27]);
> > > +       OFFSET(KVM_ARCH_FP_F_F28, kvm_cpu_context, fp.f.f[28]);
> > > +       OFFSET(KVM_ARCH_FP_F_F29, kvm_cpu_context, fp.f.f[29]);
> > > +       OFFSET(KVM_ARCH_FP_F_F30, kvm_cpu_context, fp.f.f[30]);
> > > +       OFFSET(KVM_ARCH_FP_F_F31, kvm_cpu_context, fp.f.f[31]);
> > > +       OFFSET(KVM_ARCH_FP_F_FCSR, kvm_cpu_context, fp.f.fcsr);
> > > +
> > > +       /* D extension */
> > > +
> > > +       OFFSET(KVM_ARCH_FP_D_F0, kvm_cpu_context, fp.d.f[0]);
> > > +       OFFSET(KVM_ARCH_FP_D_F1, kvm_cpu_context, fp.d.f[1]);
> > > +       OFFSET(KVM_ARCH_FP_D_F2, kvm_cpu_context, fp.d.f[2]);
> > > +       OFFSET(KVM_ARCH_FP_D_F3, kvm_cpu_context, fp.d.f[3]);
> > > +       OFFSET(KVM_ARCH_FP_D_F4, kvm_cpu_context, fp.d.f[4]);
> > > +       OFFSET(KVM_ARCH_FP_D_F5, kvm_cpu_context, fp.d.f[5]);
> > > +       OFFSET(KVM_ARCH_FP_D_F6, kvm_cpu_context, fp.d.f[6]);
> > > +       OFFSET(KVM_ARCH_FP_D_F7, kvm_cpu_context, fp.d.f[7]);
> > > +       OFFSET(KVM_ARCH_FP_D_F8, kvm_cpu_context, fp.d.f[8]);
> > > +       OFFSET(KVM_ARCH_FP_D_F9, kvm_cpu_context, fp.d.f[9]);
> > > +       OFFSET(KVM_ARCH_FP_D_F10, kvm_cpu_context, fp.d.f[10]);
> > > +       OFFSET(KVM_ARCH_FP_D_F11, kvm_cpu_context, fp.d.f[11]);
> > > +       OFFSET(KVM_ARCH_FP_D_F12, kvm_cpu_context, fp.d.f[12]);
> > > +       OFFSET(KVM_ARCH_FP_D_F13, kvm_cpu_context, fp.d.f[13]);
> > > +       OFFSET(KVM_ARCH_FP_D_F14, kvm_cpu_context, fp.d.f[14]);
> > > +       OFFSET(KVM_ARCH_FP_D_F15, kvm_cpu_context, fp.d.f[15]);
> > > +       OFFSET(KVM_ARCH_FP_D_F16, kvm_cpu_context, fp.d.f[16]);
> > > +       OFFSET(KVM_ARCH_FP_D_F17, kvm_cpu_context, fp.d.f[17]);
> > > +       OFFSET(KVM_ARCH_FP_D_F18, kvm_cpu_context, fp.d.f[18]);
> > > +       OFFSET(KVM_ARCH_FP_D_F19, kvm_cpu_context, fp.d.f[19]);
> > > +       OFFSET(KVM_ARCH_FP_D_F20, kvm_cpu_context, fp.d.f[20]);
> > > +       OFFSET(KVM_ARCH_FP_D_F21, kvm_cpu_context, fp.d.f[21]);
> > > +       OFFSET(KVM_ARCH_FP_D_F22, kvm_cpu_context, fp.d.f[22]);
> > > +       OFFSET(KVM_ARCH_FP_D_F23, kvm_cpu_context, fp.d.f[23]);
> > > +       OFFSET(KVM_ARCH_FP_D_F24, kvm_cpu_context, fp.d.f[24]);
> > > +       OFFSET(KVM_ARCH_FP_D_F25, kvm_cpu_context, fp.d.f[25]);
> > > +       OFFSET(KVM_ARCH_FP_D_F26, kvm_cpu_context, fp.d.f[26]);
> > > +       OFFSET(KVM_ARCH_FP_D_F27, kvm_cpu_context, fp.d.f[27]);
> > > +       OFFSET(KVM_ARCH_FP_D_F28, kvm_cpu_context, fp.d.f[28]);
> > > +       OFFSET(KVM_ARCH_FP_D_F29, kvm_cpu_context, fp.d.f[29]);
> > > +       OFFSET(KVM_ARCH_FP_D_F30, kvm_cpu_context, fp.d.f[30]);
> > > +       OFFSET(KVM_ARCH_FP_D_F31, kvm_cpu_context, fp.d.f[31]);
> > > +       OFFSET(KVM_ARCH_FP_D_FCSR, kvm_cpu_context, fp.d.fcsr);
> > > +
> > >         /*
> > >          * THREAD_{F,X}* might be larger than a S-type offset can handle, but
> > >          * these are used in performance-sensitive assembly so we can't resort
> > > diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> > > index f26b249eae8e..024f2c6e7582 100644
> > > --- a/arch/riscv/kvm/vcpu.c
> > > +++ b/arch/riscv/kvm/vcpu.c
> > > @@ -40,6 +40,86 @@ const struct kvm_stats_header kvm_vcpu_stats_header = {
> > >                        sizeof(kvm_vcpu_stats_desc),
> > >  };
> > >
> > > +#ifdef CONFIG_FPU
> > > +static void kvm_riscv_vcpu_fp_reset(struct kvm_vcpu *vcpu)
> > > +{
> > > +       unsigned long isa = vcpu->arch.isa;
> > > +       struct kvm_cpu_context *cntx = &vcpu->arch.guest_context;
> > > +
> > > +       cntx->sstatus &= ~SR_FS;
> > > +       if (riscv_isa_extension_available(&isa, f) ||
> > > +           riscv_isa_extension_available(&isa, d))
> > > +               cntx->sstatus |= SR_FS_INITIAL;
> > > +       else
> > > +               cntx->sstatus |= SR_FS_OFF;
> > > +}
> > > +
> > > +static void kvm_riscv_vcpu_fp_clean(struct kvm_cpu_context *cntx)
> > > +{
> > > +       cntx->sstatus &= ~SR_FS;
> > > +       cntx->sstatus |= SR_FS_CLEAN;
> > > +}
> > > +
> > > +static void kvm_riscv_vcpu_guest_fp_save(struct kvm_cpu_context *cntx,
> > > +                                        unsigned long isa)
> > > +{
> > > +       if ((cntx->sstatus & SR_FS) == SR_FS_DIRTY) {
> > > +               if (riscv_isa_extension_available(&isa, d))
> > > +                       __kvm_riscv_fp_d_save(cntx);
> > > +               else if (riscv_isa_extension_available(&isa, f))
> > > +                       __kvm_riscv_fp_f_save(cntx);
> > > +               kvm_riscv_vcpu_fp_clean(cntx);
> >
> > Hi Anup and Atish,
> > First of all, thank you very much for contributing this patch set to
> > add H extension support to the Linux kernel.
> >
> > I tried to do some development based on this patchset and encountered
> > some strange behaviors related to FPU registers. After diagnosis, I
> > suspect the root cause of these behaviors is in the
> > kvm_riscv_vcpu_fp_clean().
> > In the kvm_riscv_vcpu_fp_clean(), the sstatus.FS field of guest OS
> > will be set to clean. It will cause the guest kernel to mistakenly
> > believe the status of the FPU register is clean so that the guest OS
> > will not save the value of FPU registers to the process context before
> > this process is scheduled out. However, here the host OS only saves
> > the FPU register to the guest OS context instead of the process
> > context. In this case, for the process in the guest OS, the data in
> > FPU registers may be lost due to the lack of context saving before
> > scheduling out. Therefore, IMHO, the kvm_riscv_vcpu_fp_clean() might
> > be unnecessary and could be removed.
>
> Please don't confuse the Guest view of sstatus.FS with the Host view of
> sstatus.FS.
>
> When the Guest is running (i.e. V=1):
> 1) The Guest access to SSTATUS CSR are mapped to VSSTATUS CSR
> and the actual SSTATUS CSR (in background) represents Host SSTATUS.
> 2) The FP state (OFF, INIT, CLEAN, and DIRTY) is tracked in two FS fields
> VSSTATUS.FS (for Guest OS) and SSTATUS.FS (for Host/Hypervisor).
> 3) The RISC-V hardware will check and update both actual SSTATUS.FS
> and VSSTATUS.FS when running in Guest mode (i.e. V=1)
> 4) The Hypervisor uses actual SSTATUS.FS to save/restore FP from
> Host perspective whereas  the Guest OS uses VSSTATUS.FS to save/restore
> FP from Guest perspective
>
> The "cntx->sstatus" in KVM RISC-V code represents the actual Host
> SSTATUS CSR while Guest/VM was running and does not represent
> the Guest view of SSTATUS (which is in VSSTATUS CSR).
>
> Another way of looking at this is, Hypervisor will save/restore FP based
> on it's own view of SSTATUS.FS (i.e. actual SSTATUS CSR) while
> Guest OS will save/restore FP based on it's own view of SSTATUS.FS
> (i.e. VSSTATUS CSR). It is possible that Guest gets preempted even
> before it got chance to save FP registers so the hypervisor ensures that
> FP is saved-and-restored based on it's own view of SSTATUS.FS.
>
> The above rationale also applies to V-extension.
>
> Let us know if you still have questions related to this.
>

Hi Anup,
Thank you for the detailed explanation. I think I am really confused
between SSTATUS and VSSTATUS. Although the strange behavior
disappeared after I removed these two kvm_riscv_vcpu_fp_clean(), it is
clear that the root cause is not what I said. I will continue to find
out the root cause. Thank you.

Regards,
Vincent
> >
> > > +       }
> > > +}
> > > +
> > > +static void kvm_riscv_vcpu_guest_fp_restore(struct kvm_cpu_context *cntx,
> > > +                                           unsigned long isa)
> > > +{
> > > +       if ((cntx->sstatus & SR_FS) != SR_FS_OFF) {
> > > +               if (riscv_isa_extension_available(&isa, d))
> > > +                       __kvm_riscv_fp_d_restore(cntx);
> > > +               else if (riscv_isa_extension_available(&isa, f))
> > > +                       __kvm_riscv_fp_f_restore(cntx);
> > > +               kvm_riscv_vcpu_fp_clean(cntx);
> >
> > The reason is the same as above. Here the kvm_riscv_vcpu_fp_clean()
> > might be unnecessary and could be removed.
>
> Please see above.
>
> >
> > > +}
> > > +
> > > +static void kvm_riscv_vcpu_host_fp_save(struct kvm_cpu_context *cntx)
> > > +{
> > > +       /* No need to check host sstatus as it can be modified outside */
> > > +       if (riscv_isa_extension_available(NULL, d))
> > > +               __kvm_riscv_fp_d_save(cntx);
> > > +       else if (riscv_isa_extension_available(NULL, f))
> > > +               __kvm_riscv_fp_f_save(cntx);
> > > +}
> > > +
> > > +static void kvm_riscv_vcpu_host_fp_restore(struct kvm_cpu_context *cntx)
> > > +{
> > > +       if (riscv_isa_extension_available(NULL, d))
> > > +               __kvm_riscv_fp_d_restore(cntx);
> > > +       else if (riscv_isa_extension_available(NULL, f))
> > > +               __kvm_riscv_fp_f_restore(cntx);
> > > +}
> > > +#else
> > > +static void kvm_riscv_vcpu_fp_reset(struct kvm_vcpu *vcpu)
> > > +{
> > > +}
> > > +static void kvm_riscv_vcpu_guest_fp_save(struct kvm_cpu_context *cntx,
> > > +                                        unsigned long isa)
> > > +{
> > > +}
> > > +static void kvm_riscv_vcpu_guest_fp_restore(struct kvm_cpu_context *cntx,
> > > +                                           unsigned long isa)
> > > +{
> > > +}
> > > +static void kvm_riscv_vcpu_host_fp_save(struct kvm_cpu_context *cntx)
> > > +{
> > > +}
> > > +static void kvm_riscv_vcpu_host_fp_restore(struct kvm_cpu_context *cntx)
> > > +{
> > > +}
> > > +#endif
> > > +
> > >  #define KVM_RISCV_ISA_ALLOWED  (riscv_isa_extension_mask(a) | \
> > >                                  riscv_isa_extension_mask(c) | \
> > >                                  riscv_isa_extension_mask(d) | \
> > > @@ -60,6 +140,8 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
> > >
> > >         memcpy(cntx, reset_cntx, sizeof(*cntx));
> > >
> > > +       kvm_riscv_vcpu_fp_reset(vcpu);
> > > +
> > >         kvm_riscv_vcpu_timer_reset(vcpu);
> > >
> > >         WRITE_ONCE(vcpu->arch.irqs_pending, 0);
> > > @@ -194,6 +276,7 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
> > >                         vcpu->arch.isa = reg_val;
> > >                         vcpu->arch.isa &= riscv_isa_extension_base(NULL);
> > >                         vcpu->arch.isa &= KVM_RISCV_ISA_ALLOWED;
> > > +                       kvm_riscv_vcpu_fp_reset(vcpu);
> > >                 } else {
> > >                         return -EOPNOTSUPP;
> > >                 }
> > > @@ -598,6 +681,10 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> > >
> > >         kvm_riscv_vcpu_timer_restore(vcpu);
> > >
> > > +       kvm_riscv_vcpu_host_fp_save(&vcpu->arch.host_context);
> > > +       kvm_riscv_vcpu_guest_fp_restore(&vcpu->arch.guest_context,
> > > +                                       vcpu->arch.isa);
> > > +
> > >         vcpu->cpu = cpu;
> > >  }
> > >
> > > @@ -607,6 +694,10 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> > >
> > >         vcpu->cpu = -1;
> > >
> > > +       kvm_riscv_vcpu_guest_fp_save(&vcpu->arch.guest_context,
> > > +                                    vcpu->arch.isa);
> > > +       kvm_riscv_vcpu_host_fp_restore(&vcpu->arch.host_context);
> > > +
> > >         csr_write(CSR_HGATP, 0);
> > >
> > >         csr->vsstatus = csr_read(CSR_VSSTATUS);
> > > diff --git a/arch/riscv/kvm/vcpu_switch.S b/arch/riscv/kvm/vcpu_switch.S
> > > index e22721e1b892..029a28a195c6 100644
> > > --- a/arch/riscv/kvm/vcpu_switch.S
> > > +++ b/arch/riscv/kvm/vcpu_switch.S
> > > @@ -224,3 +224,177 @@ ENTRY(__kvm_riscv_unpriv_trap)
> > >         REG_S   a1, (KVM_ARCH_TRAP_HTINST)(a0)
> > >         sret
> > >  ENDPROC(__kvm_riscv_unpriv_trap)
> > > +
> > > +#ifdef CONFIG_FPU
> > > +       .align 3
> > > +       .global __kvm_riscv_fp_f_save
> > > +__kvm_riscv_fp_f_save:
> > > +       csrr t2, CSR_SSTATUS
> > > +       li t1, SR_FS
> > > +       csrs CSR_SSTATUS, t1
> > > +       frcsr t0
> > > +       fsw f0,  KVM_ARCH_FP_F_F0(a0)
> > > +       fsw f1,  KVM_ARCH_FP_F_F1(a0)
> > > +       fsw f2,  KVM_ARCH_FP_F_F2(a0)
> > > +       fsw f3,  KVM_ARCH_FP_F_F3(a0)
> > > +       fsw f4,  KVM_ARCH_FP_F_F4(a0)
> > > +       fsw f5,  KVM_ARCH_FP_F_F5(a0)
> > > +       fsw f6,  KVM_ARCH_FP_F_F6(a0)
> > > +       fsw f7,  KVM_ARCH_FP_F_F7(a0)
> > > +       fsw f8,  KVM_ARCH_FP_F_F8(a0)
> > > +       fsw f9,  KVM_ARCH_FP_F_F9(a0)
> > > +       fsw f10, KVM_ARCH_FP_F_F10(a0)
> > > +       fsw f11, KVM_ARCH_FP_F_F11(a0)
> > > +       fsw f12, KVM_ARCH_FP_F_F12(a0)
> > > +       fsw f13, KVM_ARCH_FP_F_F13(a0)
> > > +       fsw f14, KVM_ARCH_FP_F_F14(a0)
> > > +       fsw f15, KVM_ARCH_FP_F_F15(a0)
> > > +       fsw f16, KVM_ARCH_FP_F_F16(a0)
> > > +       fsw f17, KVM_ARCH_FP_F_F17(a0)
> > > +       fsw f18, KVM_ARCH_FP_F_F18(a0)
> > > +       fsw f19, KVM_ARCH_FP_F_F19(a0)
> > > +       fsw f20, KVM_ARCH_FP_F_F20(a0)
> > > +       fsw f21, KVM_ARCH_FP_F_F21(a0)
> > > +       fsw f22, KVM_ARCH_FP_F_F22(a0)
> > > +       fsw f23, KVM_ARCH_FP_F_F23(a0)
> > > +       fsw f24, KVM_ARCH_FP_F_F24(a0)
> > > +       fsw f25, KVM_ARCH_FP_F_F25(a0)
> > > +       fsw f26, KVM_ARCH_FP_F_F26(a0)
> > > +       fsw f27, KVM_ARCH_FP_F_F27(a0)
> > > +       fsw f28, KVM_ARCH_FP_F_F28(a0)
> > > +       fsw f29, KVM_ARCH_FP_F_F29(a0)
> > > +       fsw f30, KVM_ARCH_FP_F_F30(a0)
> > > +       fsw f31, KVM_ARCH_FP_F_F31(a0)
> > > +       sw t0, KVM_ARCH_FP_F_FCSR(a0)
> > > +       csrw CSR_SSTATUS, t2
> > > +       ret
> > > +
> > > +       .align 3
> > > +       .global __kvm_riscv_fp_d_save
> > > +__kvm_riscv_fp_d_save:
> > > +       csrr t2, CSR_SSTATUS
> > > +       li t1, SR_FS
> > > +       csrs CSR_SSTATUS, t1
> > > +       frcsr t0
> > > +       fsd f0,  KVM_ARCH_FP_D_F0(a0)
> > > +       fsd f1,  KVM_ARCH_FP_D_F1(a0)
> > > +       fsd f2,  KVM_ARCH_FP_D_F2(a0)
> > > +       fsd f3,  KVM_ARCH_FP_D_F3(a0)
> > > +       fsd f4,  KVM_ARCH_FP_D_F4(a0)
> > > +       fsd f5,  KVM_ARCH_FP_D_F5(a0)
> > > +       fsd f6,  KVM_ARCH_FP_D_F6(a0)
> > > +       fsd f7,  KVM_ARCH_FP_D_F7(a0)
> > > +       fsd f8,  KVM_ARCH_FP_D_F8(a0)
> > > +       fsd f9,  KVM_ARCH_FP_D_F9(a0)
> > > +       fsd f10, KVM_ARCH_FP_D_F10(a0)
> > > +       fsd f11, KVM_ARCH_FP_D_F11(a0)
> > > +       fsd f12, KVM_ARCH_FP_D_F12(a0)
> > > +       fsd f13, KVM_ARCH_FP_D_F13(a0)
> > > +       fsd f14, KVM_ARCH_FP_D_F14(a0)
> > > +       fsd f15, KVM_ARCH_FP_D_F15(a0)
> > > +       fsd f16, KVM_ARCH_FP_D_F16(a0)
> > > +       fsd f17, KVM_ARCH_FP_D_F17(a0)
> > > +       fsd f18, KVM_ARCH_FP_D_F18(a0)
> > > +       fsd f19, KVM_ARCH_FP_D_F19(a0)
> > > +       fsd f20, KVM_ARCH_FP_D_F20(a0)
> > > +       fsd f21, KVM_ARCH_FP_D_F21(a0)
> > > +       fsd f22, KVM_ARCH_FP_D_F22(a0)
> > > +       fsd f23, KVM_ARCH_FP_D_F23(a0)
> > > +       fsd f24, KVM_ARCH_FP_D_F24(a0)
> > > +       fsd f25, KVM_ARCH_FP_D_F25(a0)
> > > +       fsd f26, KVM_ARCH_FP_D_F26(a0)
> > > +       fsd f27, KVM_ARCH_FP_D_F27(a0)
> > > +       fsd f28, KVM_ARCH_FP_D_F28(a0)
> > > +       fsd f29, KVM_ARCH_FP_D_F29(a0)
> > > +       fsd f30, KVM_ARCH_FP_D_F30(a0)
> > > +       fsd f31, KVM_ARCH_FP_D_F31(a0)
> > > +       sw t0, KVM_ARCH_FP_D_FCSR(a0)
> > > +       csrw CSR_SSTATUS, t2
> > > +       ret
> > > +
> > > +       .align 3
> > > +       .global __kvm_riscv_fp_f_restore
> > > +__kvm_riscv_fp_f_restore:
> > > +       csrr t2, CSR_SSTATUS
> > > +       li t1, SR_FS
> > > +       lw t0, KVM_ARCH_FP_F_FCSR(a0)
> > > +       csrs CSR_SSTATUS, t1
> > > +       flw f0,  KVM_ARCH_FP_F_F0(a0)
> > > +       flw f1,  KVM_ARCH_FP_F_F1(a0)
> > > +       flw f2,  KVM_ARCH_FP_F_F2(a0)
> > > +       flw f3,  KVM_ARCH_FP_F_F3(a0)
> > > +       flw f4,  KVM_ARCH_FP_F_F4(a0)
> > > +       flw f5,  KVM_ARCH_FP_F_F5(a0)
> > > +       flw f6,  KVM_ARCH_FP_F_F6(a0)
> > > +       flw f7,  KVM_ARCH_FP_F_F7(a0)
> > > +       flw f8,  KVM_ARCH_FP_F_F8(a0)
> > > +       flw f9,  KVM_ARCH_FP_F_F9(a0)
> > > +       flw f10, KVM_ARCH_FP_F_F10(a0)
> > > +       flw f11, KVM_ARCH_FP_F_F11(a0)
> > > +       flw f12, KVM_ARCH_FP_F_F12(a0)
> > > +       flw f13, KVM_ARCH_FP_F_F13(a0)
> > > +       flw f14, KVM_ARCH_FP_F_F14(a0)
> > > +       flw f15, KVM_ARCH_FP_F_F15(a0)
> > > +       flw f16, KVM_ARCH_FP_F_F16(a0)
> > > +       flw f17, KVM_ARCH_FP_F_F17(a0)
> > > +       flw f18, KVM_ARCH_FP_F_F18(a0)
> > > +       flw f19, KVM_ARCH_FP_F_F19(a0)
> > > +       flw f20, KVM_ARCH_FP_F_F20(a0)
> > > +       flw f21, KVM_ARCH_FP_F_F21(a0)
> > > +       flw f22, KVM_ARCH_FP_F_F22(a0)
> > > +       flw f23, KVM_ARCH_FP_F_F23(a0)
> > > +       flw f24, KVM_ARCH_FP_F_F24(a0)
> > > +       flw f25, KVM_ARCH_FP_F_F25(a0)
> > > +       flw f26, KVM_ARCH_FP_F_F26(a0)
> > > +       flw f27, KVM_ARCH_FP_F_F27(a0)
> > > +       flw f28, KVM_ARCH_FP_F_F28(a0)
> > > +       flw f29, KVM_ARCH_FP_F_F29(a0)
> > > +       flw f30, KVM_ARCH_FP_F_F30(a0)
> > > +       flw f31, KVM_ARCH_FP_F_F31(a0)
> > > +       fscsr t0
> > > +       csrw CSR_SSTATUS, t2
> > > +       ret
> > > +
> > > +       .align 3
> > > +       .global __kvm_riscv_fp_d_restore
> > > +__kvm_riscv_fp_d_restore:
> > > +       csrr t2, CSR_SSTATUS
> > > +       li t1, SR_FS
> > > +       lw t0, KVM_ARCH_FP_D_FCSR(a0)
> > > +       csrs CSR_SSTATUS, t1
> > > +       fld f0,  KVM_ARCH_FP_D_F0(a0)
> > > +       fld f1,  KVM_ARCH_FP_D_F1(a0)
> > > +       fld f2,  KVM_ARCH_FP_D_F2(a0)
> > > +       fld f3,  KVM_ARCH_FP_D_F3(a0)
> > > +       fld f4,  KVM_ARCH_FP_D_F4(a0)
> > > +       fld f5,  KVM_ARCH_FP_D_F5(a0)
> > > +       fld f6,  KVM_ARCH_FP_D_F6(a0)
> > > +       fld f7,  KVM_ARCH_FP_D_F7(a0)
> > > +       fld f8,  KVM_ARCH_FP_D_F8(a0)
> > > +       fld f9,  KVM_ARCH_FP_D_F9(a0)
> > > +       fld f10, KVM_ARCH_FP_D_F10(a0)
> > > +       fld f11, KVM_ARCH_FP_D_F11(a0)
> > > +       fld f12, KVM_ARCH_FP_D_F12(a0)
> > > +       fld f13, KVM_ARCH_FP_D_F13(a0)
> > > +       fld f14, KVM_ARCH_FP_D_F14(a0)
> > > +       fld f15, KVM_ARCH_FP_D_F15(a0)
> > > +       fld f16, KVM_ARCH_FP_D_F16(a0)
> > > +       fld f17, KVM_ARCH_FP_D_F17(a0)
> > > +       fld f18, KVM_ARCH_FP_D_F18(a0)
> > > +       fld f19, KVM_ARCH_FP_D_F19(a0)
> > > +       fld f20, KVM_ARCH_FP_D_F20(a0)
> > > +       fld f21, KVM_ARCH_FP_D_F21(a0)
> > > +       fld f22, KVM_ARCH_FP_D_F22(a0)
> > > +       fld f23, KVM_ARCH_FP_D_F23(a0)
> > > +       fld f24, KVM_ARCH_FP_D_F24(a0)
> > > +       fld f25, KVM_ARCH_FP_D_F25(a0)
> > > +       fld f26, KVM_ARCH_FP_D_F26(a0)
> > > +       fld f27, KVM_ARCH_FP_D_F27(a0)
> > > +       fld f28, KVM_ARCH_FP_D_F28(a0)
> > > +       fld f29, KVM_ARCH_FP_D_F29(a0)
> > > +       fld f30, KVM_ARCH_FP_D_F30(a0)
> > > +       fld f31, KVM_ARCH_FP_D_F31(a0)
> > > +       fscsr t0
> > > +       csrw CSR_SSTATUS, t2
> > > +       ret
> > > +#endif
> > > --
> > > 2.25.1
> > >
> > >
> > > _______________________________________________
> > > linux-riscv mailing list
> > > linux-riscv@lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-riscv
>
> Regards,
> Anup