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Message-ID: <CAK9=C2X7iNd+tXaj+V3jeeBFw2dDavhf69VNtiK49tn7hYDa=g@mail.gmail.com>
Date: Sun, 17 Aug 2025 17:34:46 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Andrew Jones <ajones@...tanamicro.com>
Cc: Atish Patra <atish.patra@...ux.dev>, Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>, Alexandre Ghiti <alex@...ti.fr>,
Anup Patel <anup@...infault.org>, Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>,
kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 3/6] RISC-V: KVM: Introduce optional ONE_REG callbacks for
SBI extensions
On Sat, Aug 16, 2025 at 2:30 AM Andrew Jones <ajones@...tanamicro.com> wrote:
>
> On Thu, Aug 14, 2025 at 09:25:45PM +0530, Anup Patel wrote:
> > SBI extensions can have per-VCPU state which needs to be saved/restored
> > through ONE_REG interface for Guest/VM migration. Introduce optional
> > ONE_REG callbacks for SBI extensions so that ONE_REG implementation
> > for an SBI extenion is part of the extension sources.
> >
> > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> > ---
> > arch/riscv/include/asm/kvm_vcpu_sbi.h | 21 ++--
> > arch/riscv/kvm/vcpu_onereg.c | 31 +-----
> > arch/riscv/kvm/vcpu_sbi.c | 145 ++++++++++++++++++++++----
> > arch/riscv/kvm/vcpu_sbi_sta.c | 64 ++++++++----
> > 4 files changed, 178 insertions(+), 83 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> > index 766031e80960..144c3f6d5eb9 100644
> > --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
> > +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> > @@ -59,6 +59,15 @@ struct kvm_vcpu_sbi_extension {
> > void (*deinit)(struct kvm_vcpu *vcpu);
> >
> > void (*reset)(struct kvm_vcpu *vcpu);
> > +
> > + bool have_state;
> > + unsigned long state_reg_subtype;
> > + unsigned long (*get_state_reg_count)(struct kvm_vcpu *vcpu);
>
> I think we can drop 'have_state'. When 'get_state_reg_count' is NULL, then
> the state reg count must be zero (i.e. have_state == false).
Good suggestion. I will update in the next revision.
>
> > + int (*get_state_reg_id)(struct kvm_vcpu *vcpu, int index, u64 *reg_id);
> > + int (*get_state_reg)(struct kvm_vcpu *vcpu, unsigned long reg_num,
> > + unsigned long reg_size, void *reg_val);
> > + int (*set_state_reg)(struct kvm_vcpu *vcpu, unsigned long reg_num,
> > + unsigned long reg_size, const void *reg_val);
> > };
> >
> > void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run);
> > @@ -73,10 +82,9 @@ int kvm_riscv_vcpu_set_reg_sbi_ext(struct kvm_vcpu *vcpu,
> > const struct kvm_one_reg *reg);
> > int kvm_riscv_vcpu_get_reg_sbi_ext(struct kvm_vcpu *vcpu,
> > const struct kvm_one_reg *reg);
> > -int kvm_riscv_vcpu_set_reg_sbi(struct kvm_vcpu *vcpu,
> > - const struct kvm_one_reg *reg);
> > -int kvm_riscv_vcpu_get_reg_sbi(struct kvm_vcpu *vcpu,
> > - const struct kvm_one_reg *reg);
> > +int kvm_riscv_vcpu_reg_indices_sbi(struct kvm_vcpu *vcpu, u64 __user *uindices);
> > +int kvm_riscv_vcpu_set_reg_sbi(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
> > +int kvm_riscv_vcpu_get_reg_sbi(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
> > const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(
> > struct kvm_vcpu *vcpu, unsigned long extid);
> > bool riscv_vcpu_supports_sbi_ext(struct kvm_vcpu *vcpu, int idx);
> > @@ -85,11 +93,6 @@ void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu);
> > void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu);
> > void kvm_riscv_vcpu_sbi_reset(struct kvm_vcpu *vcpu);
> >
> > -int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu, unsigned long reg_num,
> > - unsigned long *reg_val);
> > -int kvm_riscv_vcpu_set_reg_sbi_sta(struct kvm_vcpu *vcpu, unsigned long reg_num,
> > - unsigned long reg_val);
> > -
> > #ifdef CONFIG_RISCV_SBI_V01
> > extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_v01;
> > #endif
> > diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
> > index b77748a56a59..5843b0519224 100644
> > --- a/arch/riscv/kvm/vcpu_onereg.c
> > +++ b/arch/riscv/kvm/vcpu_onereg.c
> > @@ -1090,36 +1090,9 @@ static unsigned long num_sbi_ext_regs(struct kvm_vcpu *vcpu)
> > return copy_sbi_ext_reg_indices(vcpu, NULL);
> > }
> >
> > -static int copy_sbi_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
> > -{
> > - struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
> > - int total = 0;
> > -
> > - if (scontext->ext_status[KVM_RISCV_SBI_EXT_STA] == KVM_RISCV_SBI_EXT_STATUS_ENABLED) {
> > - u64 size = IS_ENABLED(CONFIG_32BIT) ? KVM_REG_SIZE_U32 : KVM_REG_SIZE_U64;
> > - int n = sizeof(struct kvm_riscv_sbi_sta) / sizeof(unsigned long);
> > -
> > - for (int i = 0; i < n; i++) {
> > - u64 reg = KVM_REG_RISCV | size |
> > - KVM_REG_RISCV_SBI_STATE |
> > - KVM_REG_RISCV_SBI_STA | i;
> > -
> > - if (uindices) {
> > - if (put_user(reg, uindices))
> > - return -EFAULT;
> > - uindices++;
> > - }
> > - }
> > -
> > - total += n;
> > - }
> > -
> > - return total;
> > -}
> > -
> > static inline unsigned long num_sbi_regs(struct kvm_vcpu *vcpu)
> > {
> > - return copy_sbi_reg_indices(vcpu, NULL);
> > + return kvm_riscv_vcpu_reg_indices_sbi(vcpu, NULL);
> > }
> >
> > static inline unsigned long num_vector_regs(const struct kvm_vcpu *vcpu)
> > @@ -1247,7 +1220,7 @@ int kvm_riscv_vcpu_copy_reg_indices(struct kvm_vcpu *vcpu,
> > return ret;
> > uindices += ret;
> >
> > - ret = copy_sbi_reg_indices(vcpu, uindices);
> > + ret = kvm_riscv_vcpu_reg_indices_sbi(vcpu, uindices);
> > if (ret < 0)
> > return ret;
> > uindices += ret;
> > diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> > index 01a93f4fdb16..8b3c393e0c83 100644
> > --- a/arch/riscv/kvm/vcpu_sbi.c
> > +++ b/arch/riscv/kvm/vcpu_sbi.c
> > @@ -364,64 +364,163 @@ int kvm_riscv_vcpu_get_reg_sbi_ext(struct kvm_vcpu *vcpu,
> > return 0;
> > }
> >
> > -int kvm_riscv_vcpu_set_reg_sbi(struct kvm_vcpu *vcpu,
> > - const struct kvm_one_reg *reg)
> > +int kvm_riscv_vcpu_reg_indices_sbi(struct kvm_vcpu *vcpu, u64 __user *uindices)
> > +{
> > + struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
> > + const struct kvm_riscv_sbi_extension_entry *entry;
> > + const struct kvm_vcpu_sbi_extension *ext;
> > + unsigned long state_reg_count;
> > + int i, j, rc, count = 0;
> > + u64 reg;
> > +
> > + for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
> > + entry = &sbi_ext[i];
> > + ext = entry->ext_ptr;
> > +
> > + if (!ext->have_state ||
> > + scontext->ext_status[entry->ext_idx] != KVM_RISCV_SBI_EXT_STATUS_ENABLED)
> > + continue;
> > +
> > + state_reg_count = ext->get_state_reg_count(vcpu);
> > + if (!uindices)
> > + goto skip_put_user;
> > +
> > + for (j = 0; j < state_reg_count; j++) {
> > + if (ext->get_state_reg_id) {
> > + rc = ext->get_state_reg_id(vcpu, j, ®);
> > + if (rc)
> > + return rc;
> > + } else {
> > + reg = KVM_REG_RISCV |
> > + (IS_ENABLED(CONFIG_32BIT) ?
> > + KVM_REG_SIZE_U32 : KVM_REG_SIZE_U64) |
> > + KVM_REG_RISCV_SBI_STATE |
> > + ext->state_reg_subtype | j;
> > + }
> > +
> > + if (put_user(reg, uindices))
> > + return -EFAULT;
> > + uindices++;
> > + }
> > +
> > +skip_put_user:
> > + count += state_reg_count;
> > + }
> > +
> > + return count;
> > +}
> > +
> > +static const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext_withstate(struct kvm_vcpu *vcpu,
> > + unsigned long subtype)
> > +{
> > + struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
> > + const struct kvm_riscv_sbi_extension_entry *entry;
> > + const struct kvm_vcpu_sbi_extension *ext;
> > + int i;
> > +
> > + for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
> > + entry = &sbi_ext[i];
> > + ext = entry->ext_ptr;
> > +
> > + if (ext->have_state &&
> > + ext->state_reg_subtype == subtype &&
> > + scontext->ext_status[entry->ext_idx] == KVM_RISCV_SBI_EXT_STATUS_ENABLED)
> > + return ext;
> > + }
> > +
> > + return NULL;
> > +}
> > +
> > +int kvm_riscv_vcpu_set_reg_sbi(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> > {
> > 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_SBI_STATE);
> > - unsigned long reg_subtype, reg_val;
> > -
> > - if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
> > + const struct kvm_vcpu_sbi_extension *ext;
> > + unsigned long reg_subtype;
> > + void *reg_val;
> > + u64 data64;
> > + u32 data32;
> > + u16 data16;
> > + u8 data8;
> > +
> > + switch (KVM_REG_SIZE(reg->id)) {
> > + case 1:
> > + reg_val = &data8;
> > + break;
> > + case 2:
> > + reg_val = &data16;
> > + break;
> > + case 4:
> > + reg_val = &data32;
> > + break;
> > + case 8:
> > + reg_val = &data64;
> > + break;
> > + default:
> > return -EINVAL;
> > + };
>
> superfluous ';'
Okay, I will update in the next revision.
>
> >
> > - if (copy_from_user(®_val, uaddr, KVM_REG_SIZE(reg->id)))
> > + if (copy_from_user(reg_val, uaddr, KVM_REG_SIZE(reg->id)))
> > return -EFAULT;
> >
> > reg_subtype = reg_num & KVM_REG_RISCV_SUBTYPE_MASK;
> > reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;
> >
> > - switch (reg_subtype) {
> > - case KVM_REG_RISCV_SBI_STA:
> > - return kvm_riscv_vcpu_set_reg_sbi_sta(vcpu, reg_num, reg_val);
> > - default:
> > + ext = kvm_vcpu_sbi_find_ext_withstate(vcpu, reg_subtype);
> > + if (!ext || !ext->set_state_reg)
> > return -EINVAL;
> > - }
> >
> > - return 0;
> > + return ext->set_state_reg(vcpu, reg_num, KVM_REG_SIZE(reg->id), reg_val);
> > }
> >
> > -int kvm_riscv_vcpu_get_reg_sbi(struct kvm_vcpu *vcpu,
> > - const struct kvm_one_reg *reg)
> > +int kvm_riscv_vcpu_get_reg_sbi(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> > {
> > 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_SBI_STATE);
> > - unsigned long reg_subtype, reg_val;
> > + const struct kvm_vcpu_sbi_extension *ext;
> > + unsigned long reg_subtype;
> > + void *reg_val;
> > + u64 data64;
> > + u32 data32;
> > + u16 data16;
> > + u8 data8;
> > int ret;
> >
> > - if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
> > + switch (KVM_REG_SIZE(reg->id)) {
> > + case 1:
> > + reg_val = &data8;
> > + break;
> > + case 2:
> > + reg_val = &data16;
> > + break;
> > + case 4:
> > + reg_val = &data32;
> > + break;
> > + case 8:
> > + reg_val = &data64;
> > + break;
> > + default:
> > return -EINVAL;
> > + };
>
> superfluous ';'
Okay, I will update in the next revision.
>
> >
> > reg_subtype = reg_num & KVM_REG_RISCV_SUBTYPE_MASK;
> > reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;
> >
> > - switch (reg_subtype) {
> > - case KVM_REG_RISCV_SBI_STA:
> > - ret = kvm_riscv_vcpu_get_reg_sbi_sta(vcpu, reg_num, ®_val);
> > - break;
> > - default:
> > + ext = kvm_vcpu_sbi_find_ext_withstate(vcpu, reg_subtype);
> > + if (!ext || !ext->get_state_reg)
> > return -EINVAL;
> > - }
> >
> > + ret = ext->get_state_reg(vcpu, reg_num, KVM_REG_SIZE(reg->id), reg_val);
> > if (ret)
> > return ret;
> >
> > - if (copy_to_user(uaddr, ®_val, KVM_REG_SIZE(reg->id)))
> > + if (copy_to_user(uaddr, reg_val, KVM_REG_SIZE(reg->id)))
> > return -EFAULT;
> >
> > return 0;
> > diff --git a/arch/riscv/kvm/vcpu_sbi_sta.c b/arch/riscv/kvm/vcpu_sbi_sta.c
> > index cc6cb7c8f0e4..d14cf6255d83 100644
> > --- a/arch/riscv/kvm/vcpu_sbi_sta.c
> > +++ b/arch/riscv/kvm/vcpu_sbi_sta.c
> > @@ -151,63 +151,83 @@ static unsigned long kvm_sbi_ext_sta_probe(struct kvm_vcpu *vcpu)
> > return !!sched_info_on();
> > }
> >
> > -const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta = {
> > - .extid_start = SBI_EXT_STA,
> > - .extid_end = SBI_EXT_STA,
> > - .handler = kvm_sbi_ext_sta_handler,
> > - .probe = kvm_sbi_ext_sta_probe,
> > - .reset = kvm_riscv_vcpu_sbi_sta_reset,
> > -};
> > +static unsigned long kvm_sbi_ext_sta_get_state_reg_count(struct kvm_vcpu *vcpu)
> > +{
> > + return sizeof(struct kvm_riscv_sbi_sta) / sizeof(unsigned long);
> > +}
> >
> > -int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu,
> > - unsigned long reg_num,
> > - unsigned long *reg_val)
> > +static int kvm_sbi_ext_sta_get_reg(struct kvm_vcpu *vcpu, unsigned long reg_num,
> > + unsigned long reg_size, void *reg_val)
> > {
> > + unsigned long *value;
> > +
> > + if (reg_size != sizeof(unsigned long))
> > + return -EINVAL;
> > + value = reg_val;
> > +
> > switch (reg_num) {
> > case KVM_REG_RISCV_SBI_STA_REG(shmem_lo):
> > - *reg_val = (unsigned long)vcpu->arch.sta.shmem;
> > + *value = (unsigned long)vcpu->arch.sta.shmem;
> > break;
> > case KVM_REG_RISCV_SBI_STA_REG(shmem_hi):
> > if (IS_ENABLED(CONFIG_32BIT))
> > - *reg_val = upper_32_bits(vcpu->arch.sta.shmem);
> > + *value = upper_32_bits(vcpu->arch.sta.shmem);
> > else
> > - *reg_val = 0;
> > + *value = 0;
> > break;
> > default:
> > - return -EINVAL;
> > + return -ENOENT;
> > }
> >
> > return 0;
> > }
> >
> > -int kvm_riscv_vcpu_set_reg_sbi_sta(struct kvm_vcpu *vcpu,
> > - unsigned long reg_num,
> > - unsigned long reg_val)
> > +static int kvm_sbi_ext_sta_set_reg(struct kvm_vcpu *vcpu, unsigned long reg_num,
> > + unsigned long reg_size, const void *reg_val)
> > {
> > + unsigned long value;
> > +
> > + if (reg_size != sizeof(unsigned long))
> > + return -EINVAL;
> > + value = *(const unsigned long *)reg_val;
> > +
> > switch (reg_num) {
> > case KVM_REG_RISCV_SBI_STA_REG(shmem_lo):
> > if (IS_ENABLED(CONFIG_32BIT)) {
> > gpa_t hi = upper_32_bits(vcpu->arch.sta.shmem);
> >
> > - vcpu->arch.sta.shmem = reg_val;
> > + vcpu->arch.sta.shmem = value;
> > vcpu->arch.sta.shmem |= hi << 32;
> > } else {
> > - vcpu->arch.sta.shmem = reg_val;
> > + vcpu->arch.sta.shmem = value;
> > }
> > break;
> > case KVM_REG_RISCV_SBI_STA_REG(shmem_hi):
> > if (IS_ENABLED(CONFIG_32BIT)) {
> > gpa_t lo = lower_32_bits(vcpu->arch.sta.shmem);
> >
> > - vcpu->arch.sta.shmem = ((gpa_t)reg_val << 32);
> > + vcpu->arch.sta.shmem = ((gpa_t)value << 32);
> > vcpu->arch.sta.shmem |= lo;
> > - } else if (reg_val != 0) {
> > + } else if (value != 0) {
> > return -EINVAL;
> > }
> > break;
> > default:
> > - return -EINVAL;
> > + return -ENOENT;
> > }
> >
> > return 0;
> > }
> > +
> > +const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta = {
> > + .extid_start = SBI_EXT_STA,
> > + .extid_end = SBI_EXT_STA,
> > + .handler = kvm_sbi_ext_sta_handler,
> > + .probe = kvm_sbi_ext_sta_probe,
> > + .reset = kvm_riscv_vcpu_sbi_sta_reset,
> > + .have_state = true,
> > + .state_reg_subtype = KVM_REG_RISCV_SBI_STA,
> > + .get_state_reg_count = kvm_sbi_ext_sta_get_state_reg_count,
> > + .get_state_reg = kvm_sbi_ext_sta_get_reg,
> > + .set_state_reg = kvm_sbi_ext_sta_set_reg,
> > +};
> > --
> > 2.43.0
> >
>
> Otherwise,
>
> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
>
Thanks,
Anup
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