From: Anup Patel <anup@brainfault.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Damien Le Moal <Damien.LeMoal@wdc.com>,
Palmer Dabbelt <palmer@sifive.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Radim K <rkrcmar@redhat.com>, Anup Patel <Anup.Patel@wdc.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@infradead.org>,
Atish Patra <Atish.Patra@wdc.com>,
Alistair Francis <Alistair.Francis@wdc.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Thomas Gleixner <tglx@linutronix.de>,
"linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>
Subject: Re: [RFC PATCH v2 08/19] RISC-V: KVM: Implement VCPU world-switch
Date: Fri, 2 Aug 2019 14:13:52 +0530 [thread overview]
Message-ID: <CAAhSdy2_ZsnT7gSKb624r9wzuJSx+1TnKxgW6srtqvXV1Ri9Aw@mail.gmail.com> (raw)
In-Reply-To: <72d8efbf-ec62-ab1e-68bf-e0c5f0bc256e@redhat.com>
On Fri, Aug 2, 2019 at 2:00 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 02/08/19 09:47, Anup Patel wrote:
> > + /* Save Host SSTATUS, HSTATUS, SCRATCH and STVEC */
> > + csrr t0, CSR_SSTATUS
> > + REG_S t0, (KVM_ARCH_HOST_SSTATUS)(a0)
> > + csrr t1, CSR_HSTATUS
> > + REG_S t1, (KVM_ARCH_HOST_HSTATUS)(a0)
> > + csrr t2, CSR_SSCRATCH
> > + REG_S t2, (KVM_ARCH_HOST_SSCRATCH)(a0)
> > + csrr t3, CSR_STVEC
> > + REG_S t3, (KVM_ARCH_HOST_STVEC)(a0)
> > +
>
> A possible optimization: if these cannot change while Linux runs (I am
> thinking especially of STVEC and HSTATUS, but perhaps SSCRATCH can be
> saved on kvm_arch_vcpu_load too) you can avoid the csrr and store.
Actual exception vector of Host Linux is different so we switch STVEC
every time.
HSTATUS.SPV is set whenever we come back from Guest world so
while we are in in-kernel run loop with interrupts enabled we can get
external interrupt and HSTATUS.SPV bit can affect SRET of interrupt
handler. To handle this we switch HSTATUS every time.
The world switch code uses SSCRATCH to save vcpu->arch pointer
which is later used on return path. Now, I did not want to restrict Host
Linux from using SSCRATCH for some other purpose hence we
switch SSCRATCH every time.
Regards,
Anup
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next prev parent reply other threads:[~2019-08-02 8:44 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
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 [this message]
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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