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Message-ID: <CAK9=C2VQF8kKfVztBR2hrANb63Q8s0+Md6ZDXFjLWjWED1A2zA@mail.gmail.com>
Date: Fri, 27 Jan 2023 21:25:23 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Andrew Jones <ajones@...tanamicro.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Atish Patra <atishp@...shpatra.org>,
Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Anup Patel <anup@...infault.org>, kvm@...r.kernel.org,
kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] RISC-V: KVM: Add ONE_REG interface for AIA CSRs
On Thu, Jan 26, 2023 at 10:49 PM Andrew Jones <ajones@...tanamicro.com> wrote:
>
> On Thu, Jan 12, 2023 at 07:33:02PM +0530, Anup Patel wrote:
> > We extend the CSR ONE_REG interface to access both general CSRs and
> > AIA CSRs. To achieve this, we introduce "subtype" field in the ONE_REG
> > id which can be used for grouping registers within a particular "type"
> > of ONE_REG registers.
> >
> > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> > ---
> > arch/riscv/include/uapi/asm/kvm.h | 15 ++++-
> > arch/riscv/kvm/vcpu.c | 96 ++++++++++++++++++++++++-------
> > 2 files changed, 89 insertions(+), 22 deletions(-)
> >
> > diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> > index 71992ff1f9dd..d0704eff0121 100644
> > --- a/arch/riscv/include/uapi/asm/kvm.h
> > +++ b/arch/riscv/include/uapi/asm/kvm.h
> > @@ -64,7 +64,7 @@ struct kvm_riscv_core {
> > #define KVM_RISCV_MODE_S 1
> > #define KVM_RISCV_MODE_U 0
> >
> > -/* CSR registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
> > +/* General CSR registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
> > struct kvm_riscv_csr {
> > unsigned long sstatus;
> > unsigned long sie;
> > @@ -78,6 +78,10 @@ struct kvm_riscv_csr {
> > unsigned long scounteren;
> > };
> >
> > +/* AIA CSR registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
> > +struct kvm_riscv_aia_csr {
> > +};
> > +
> > /* TIMER registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
> > struct kvm_riscv_timer {
> > __u64 frequency;
> > @@ -105,6 +109,7 @@ enum KVM_RISCV_ISA_EXT_ID {
> > KVM_RISCV_ISA_EXT_SVINVAL,
> > KVM_RISCV_ISA_EXT_ZIHINTPAUSE,
> > KVM_RISCV_ISA_EXT_ZICBOM,
> > + KVM_RISCV_ISA_EXT_SSAIA,
> > KVM_RISCV_ISA_EXT_MAX,
> > };
> >
> > @@ -134,6 +139,8 @@ enum KVM_RISCV_SBI_EXT_ID {
> > /* If you need to interpret the index values, here is the key: */
> > #define KVM_REG_RISCV_TYPE_MASK 0x00000000FF000000
> > #define KVM_REG_RISCV_TYPE_SHIFT 24
> > +#define KVM_REG_RISCV_SUBTYPE_MASK 0x0000000000FF0000
> > +#define KVM_REG_RISCV_SUBTYPE_SHIFT 16
>
> We could just define a new AIA_CSR type, rather than introduce CSR
> subtypes. While grouping all CSRs together under the CSR type also
> makes sense, having to teach all userspaces about subtypes may not
> be worth the organizational benefits.
My main concern is that we have chosen a 8-bit wide "type" field
in ONE_REG id which can't be changed now and it will be consumed
very fast if we start adding separate "type" for each ISA extension.
This "type" field is shared with SBI extensions and we will be also
having separate nested CSR state for various ISA extensions.
Since KVM RISC-V is young, I think it is better to introduce a
"subtype" field now so that we have ample space for the future.
Also, both ONE_REG "type" and "subtype" are arch specific fields
of ONE_REG id so all KVM user space changes will be contained
in RISC-V specific code.
>
> >
> > /* Config registers are mapped as type 1 */
> > #define KVM_REG_RISCV_CONFIG (0x01 << KVM_REG_RISCV_TYPE_SHIFT)
> > @@ -147,8 +154,12 @@ enum KVM_RISCV_SBI_EXT_ID {
> >
> > /* Control and status registers are mapped as type 3 */
> > #define KVM_REG_RISCV_CSR (0x03 << KVM_REG_RISCV_TYPE_SHIFT)
> > +#define KVM_REG_RISCV_CSR_GENERAL 0x0
> > +#define KVM_REG_RISCV_CSR_AIA 0x1
> > #define KVM_REG_RISCV_CSR_REG(name) \
> > - (offsetof(struct kvm_riscv_csr, name) / sizeof(unsigned long))
> > + (offsetof(struct kvm_riscv_csr, name) / sizeof(unsigned long))
> > +#define KVM_REG_RISCV_CSR_AIA_REG(name) \
> > + (offsetof(struct kvm_riscv_aia_csr, name) / sizeof(unsigned long))
> >
> > /* Timer registers are mapped as type 4 */
> > #define KVM_REG_RISCV_TIMER (0x04 << KVM_REG_RISCV_TYPE_SHIFT)
> > diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> > index 3cf50eadc8ce..37933ea20274 100644
> > --- a/arch/riscv/kvm/vcpu.c
> > +++ b/arch/riscv/kvm/vcpu.c
> > @@ -58,6 +58,7 @@ static const unsigned long kvm_isa_ext_arr[] = {
> > [KVM_RISCV_ISA_EXT_I] = RISCV_ISA_EXT_i,
> > [KVM_RISCV_ISA_EXT_M] = RISCV_ISA_EXT_m,
> >
> > + KVM_ISA_EXT_ARR(SSAIA),
> > KVM_ISA_EXT_ARR(SSTC),
> > KVM_ISA_EXT_ARR(SVINVAL),
> > KVM_ISA_EXT_ARR(SVPBMT),
> > @@ -96,6 +97,7 @@ static bool kvm_riscv_vcpu_isa_disable_allowed(unsigned long ext)
> > case KVM_RISCV_ISA_EXT_C:
> > case KVM_RISCV_ISA_EXT_I:
> > case KVM_RISCV_ISA_EXT_M:
> > + case KVM_RISCV_ISA_EXT_SSAIA:
> > case KVM_RISCV_ISA_EXT_SSTC:
> > case KVM_RISCV_ISA_EXT_SVINVAL:
> > case KVM_RISCV_ISA_EXT_ZIHINTPAUSE:
> > @@ -451,30 +453,79 @@ static int kvm_riscv_vcpu_set_reg_core(struct kvm_vcpu *vcpu,
> > return 0;
> > }
> >
> > +static int kvm_riscv_vcpu_general_get_csr(struct kvm_vcpu *vcpu,
> > + unsigned long reg_num,
> > + unsigned long *out_val)
> > +{
> > + struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> > +
> > + if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
> > + return -EINVAL;
> > +
> > + if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
> > + kvm_riscv_vcpu_flush_interrupts(vcpu);
> > + *out_val = (csr->hvip >> VSIP_TO_HVIP_SHIFT) & VSIP_VALID_MASK;
> > + } else
> > + *out_val = ((unsigned long *)csr)[reg_num];
> > +
> > + return 0;
> > +}
> > +
> > static int kvm_riscv_vcpu_get_reg_csr(struct kvm_vcpu *vcpu,
> > const struct kvm_one_reg *reg)
> > {
> > - struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> > + int rc;
> > unsigned long __user *uaddr =
> > (unsigned long __user *)(unsigned long)reg->addr;
> > unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
> > KVM_REG_SIZE_MASK |
> > KVM_REG_RISCV_CSR);
> > - unsigned long reg_val;
> > + unsigned long reg_val, reg_subtype;
> >
> > if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
> > return -EINVAL;
> > +
> > + reg_subtype = (reg_num & KVM_REG_RISCV_SUBTYPE_MASK)
> > + >> KVM_REG_RISCV_SUBTYPE_SHIFT;
> > + reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;
> > + switch (reg_subtype) {
> > + case KVM_REG_RISCV_CSR_GENERAL:
> > + rc = kvm_riscv_vcpu_general_get_csr(vcpu, reg_num, ®_val);
> > + break;
> > + case KVM_REG_RISCV_CSR_AIA:
> > + rc = kvm_riscv_vcpu_aia_get_csr(vcpu, reg_num, ®_val);
> > + break;
> > + default:
> > + rc = -EINVAL;
> > + break;
> > + }
> > + if (rc)
> > + return rc;
> > +
> > + if (copy_to_user(uaddr, ®_val, KVM_REG_SIZE(reg->id)))
> > + return -EFAULT;
> > +
> > + return 0;
> > +}
> > +
> > +static inline int kvm_riscv_vcpu_general_set_csr(struct kvm_vcpu *vcpu,
> > + unsigned long reg_num,
> > + unsigned long reg_val)
> > +{
> > + struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> > +
> > if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
> > return -EINVAL;
> >
> > if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
> > - kvm_riscv_vcpu_flush_interrupts(vcpu);
> > - reg_val = (csr->hvip >> VSIP_TO_HVIP_SHIFT) & VSIP_VALID_MASK;
> > - } else
> > - reg_val = ((unsigned long *)csr)[reg_num];
> > + reg_val &= VSIP_VALID_MASK;
> > + reg_val <<= VSIP_TO_HVIP_SHIFT;
> > + }
> >
> > - if (copy_to_user(uaddr, ®_val, KVM_REG_SIZE(reg->id)))
> > - return -EFAULT;
> > + ((unsigned long *)csr)[reg_num] = reg_val;
> > +
> > + if (reg_num == KVM_REG_RISCV_CSR_REG(sip))
> > + WRITE_ONCE(vcpu->arch.irqs_pending_mask, 0);
> >
> > return 0;
> > }
> > @@ -482,31 +533,36 @@ static int kvm_riscv_vcpu_get_reg_csr(struct kvm_vcpu *vcpu,
> > static int kvm_riscv_vcpu_set_reg_csr(struct kvm_vcpu *vcpu,
> > const struct kvm_one_reg *reg)
> > {
> > - struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> > + int rc;
> > unsigned long __user *uaddr =
> > (unsigned long __user *)(unsigned long)reg->addr;
> > unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
> > KVM_REG_SIZE_MASK |
> > KVM_REG_RISCV_CSR);
> > - unsigned long reg_val;
> > + unsigned long reg_val, reg_subtype;
> >
> > if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
> > return -EINVAL;
> > - if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
> > - return -EINVAL;
> >
> > if (copy_from_user(®_val, uaddr, KVM_REG_SIZE(reg->id)))
> > return -EFAULT;
> >
> > - if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
> > - reg_val &= VSIP_VALID_MASK;
> > - reg_val <<= VSIP_TO_HVIP_SHIFT;
> > + reg_subtype = (reg_num & KVM_REG_RISCV_SUBTYPE_MASK)
> > + >> KVM_REG_RISCV_SUBTYPE_SHIFT;
> > + reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;
> > + switch (reg_subtype) {
> > + case KVM_REG_RISCV_CSR_GENERAL:
> > + rc = kvm_riscv_vcpu_general_set_csr(vcpu, reg_num, reg_val);
> > + break;
> > + case KVM_REG_RISCV_CSR_AIA:
> > + rc = kvm_riscv_vcpu_aia_set_csr(vcpu, reg_num, reg_val);
> > + break;
> > + default:
> > + rc = -EINVAL;
> > + break;
> > }
> > -
> > - ((unsigned long *)csr)[reg_num] = reg_val;
> > -
> > - if (reg_num == KVM_REG_RISCV_CSR_REG(sip))
> > - WRITE_ONCE(vcpu->arch.irqs_pending_mask, 0);
> > + if (rc)
> > + return rc;
> >
> > return 0;
> > }
> > --
> > 2.34.1
> >
>
> Thanks,
> drew
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