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From: Anup Patel <anup@brainfault.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Anup Patel <Anup.Patel@wdc.com>,
	Palmer Dabbelt <palmer@sifive.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Radim K <rkrcmar@redhat.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Atish Patra <Atish.Patra@wdc.com>,
	Alistair Francis <Alistair.Francis@wdc.com>,
	Damien Le Moal <Damien.LeMoal@wdc.com>,
	Christoph Hellwig <hch@infradead.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v2 07/19] RISC-V: KVM: Implement KVM_GET_ONE_REG/KVM_SET_ONE_REG ioctls
Date: Mon, 5 Aug 2019 12:25:20 +0530	[thread overview]
Message-ID: <CAAhSdy3hdWfUCUEK-idoTzgB2hKeAd3FzsHEH1DK_BTC_KGdJw@mail.gmail.com> (raw)
In-Reply-To: <03f60f3a-bb50-9210-8352-da16cca322b9@redhat.com>

On Fri, Aug 2, 2019 at 2:33 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 02/08/19 09:47, Anup Patel wrote:
> > +     if (reg_num == KVM_REG_RISCV_CSR_REG(sip))
> > +             kvm_riscv_vcpu_flush_interrupts(vcpu, false);
>
> Not updating the vsip CSR here can cause an interrupt to be lost, if the
> next call to kvm_riscv_vcpu_flush_interrupts finds a zero mask.

Thanks for catching this issue. I will address it in v3.

If we think more on similar lines then we also need to handle the case
where Guest VCPU had pending interrupts and we suddenly stopped it
for Guest migration. In this case, we would eventually use SET_ONE_REG
ioctl on destination Host which should set vsip_shadow instead of vsip so
that we force update HW after resuming Guest VCPU on destination host.

>
> You could add a new field vcpu->vsip_shadow that is updated every time
> CSR_VSIP is written (including kvm_arch_vcpu_load) with a function like
>
> void kvm_riscv_update_vsip(struct kvm_vcpu *vcpu)
> {
>         if (vcpu->vsip_shadow != vcpu->arch.guest_csr.vsip) {
>                 csr_write(CSR_VSIP, vcpu->arch.guest_csr.vsip);
>                 vcpu->vsip_shadow = vcpu->arch.guest_csr.vsip;
>         }
> }
>
> And just call this unconditionally from kvm_vcpu_ioctl_run.  The cost is
> just a memory load per VS-mode entry, it should hardly be measurable.
>

I think we can do this at start of kvm_riscv_vcpu_flush_interrupts() as well.

Regards,
Anup

  reply	other threads:[~2019-08-05  6:55 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-02  7:46 [RFC PATCH v2 00/19] KVM RISC-V Support Anup Patel
2019-08-02  7:47 ` [RFC PATCH v2 01/19] KVM: RISC-V: Add KVM_REG_RISCV for ONE_REG interface Anup Patel
2019-08-02  7:47 ` [RFC PATCH v2 02/19] RISC-V: Export few kernel symbols Anup Patel
2019-08-02  7:47 ` [RFC PATCH v2 03/19] RISC-V: Add hypervisor extension related CSR defines Anup Patel
2019-08-02  7:47 ` [RFC PATCH v2 04/19] RISC-V: Add initial skeletal KVM support Anup Patel
2019-08-02  9:01   ` Paolo Bonzini
2019-08-05  5:48     ` Anup Patel
2019-08-02  7:47 ` [RFC PATCH v2 05/19] RISC-V: KVM: Implement VCPU create, init and destroy functions Anup Patel
2019-08-02  7:47 ` [RFC PATCH v2 06/19] RISC-V: KVM: Implement VCPU interrupts and requests handling Anup Patel
2019-08-02  8:17   ` Paolo Bonzini
2019-08-05 12:27     ` Anup Patel
2019-08-02  7:47 ` [RFC PATCH v2 07/19] RISC-V: KVM: Implement KVM_GET_ONE_REG/KVM_SET_ONE_REG ioctls Anup Patel
2019-08-02  9:03   ` Paolo Bonzini
2019-08-05  6:55     ` Anup Patel [this message]
2019-08-05  7:10       ` Paolo Bonzini
2019-08-05 11:00         ` Anup Patel
2019-08-05 11:07           ` Paolo Bonzini
2019-08-05 11:37   ` Christian Borntraeger
2019-08-05 11:56     ` Anup Patel
2019-08-05 12:01       ` Paolo Bonzini
2019-08-05 12:13         ` Anup Patel
2019-08-05 11:56     ` Paolo Bonzini
2019-08-02  7:47 ` [RFC PATCH v2 08/19] RISC-V: KVM: Implement VCPU world-switch Anup Patel
2019-08-02  8:30   ` Paolo Bonzini
2019-08-02  8:43     ` Anup Patel
2019-08-02  8:59       ` Paolo Bonzini
2019-08-02  7:47 ` [RFC PATCH v2 09/19] RISC-V: KVM: Handle MMIO exits for VCPU Anup Patel
2019-08-02  7:47 ` [RFC PATCH v2 10/19] RISC-V: KVM: Handle WFI " Anup Patel
2019-08-02  9:03   ` Paolo Bonzini
2019-08-05  7:12     ` Anup Patel
2019-08-05  7:14       ` Paolo Bonzini
2019-08-05  7:18         ` Anup Patel
2019-08-02  7:48 ` [RFC PATCH v2 11/19] RISC-V: KVM: Implement VMID allocator Anup Patel
2019-08-02  9:19   ` Paolo Bonzini
2019-08-05 10:07     ` Anup Patel
2019-08-02  7:48 ` [RFC PATCH v2 12/19] RISC-V: KVM: Implement stage2 page table programming Anup Patel
2019-08-02  9:14   ` Paolo Bonzini
2019-08-05 10:08     ` Anup Patel
2019-08-02  7:48 ` [RFC PATCH v2 13/19] RISC-V: KVM: Implement MMU notifiers Anup Patel
2019-08-02  7:48 ` [RFC PATCH v2 14/19] RISC-V: KVM: Add timer functionality Anup Patel
2019-08-02  7:48 ` [RFC PATCH v2 15/19] RISC-V: KVM: FP lazy save/restore Anup Patel
2019-08-02  7:48 ` [RFC PATCH v2 16/19] RISC-V: KVM: Implement ONE REG interface for FP registers Anup Patel
2019-08-02  7:48 ` [RFC PATCH v2 17/19] RISC-V: KVM: Add SBI v0.1 support Anup Patel
2019-08-02  7:48 ` [RFC PATCH v2 18/19] RISC-V: Enable VIRTIO drivers in RV64 and RV32 defconfig Anup Patel
2019-08-02  7:48 ` [RFC PATCH v2 19/19] RISC-V: KVM: Add MAINTAINERS entry Anup Patel
2019-08-02  9:22 ` [RFC PATCH v2 00/19] KVM RISC-V Support Paolo Bonzini

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