Re: [PATCH v2 2/4] KVM: hyper-v: Collect hypercall params into struct

From: Vitaly Kuznetsov
Date: Tue Apr 13 2021 - 09:53:20 EST

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In reply to: Siddharth Chandrasekaran: "[PATCH v2 2/4] KVM: hyper-v: Collect hypercall params into struct"
Next in thread: Siddharth Chandrasekaran: "Re: [PATCH v2 2/4] KVM: hyper-v: Collect hypercall params into struct"
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Siddharth Chandrasekaran <sidcha@xxxxxxxxx> writes:

> As of now there are 7 parameters (and flags) that are used in various
> hyper-v hypercall handlers. There are 6 more input/output parameters
> passed from XMM registers which are to be added in an upcoming patch.
>
> To make passing arguments to the handlers more readable, capture all
> these parameters into a single structure.
>
> Cc: Alexander Graf <graf@xxxxxxxxxx>
> Cc: Evgeny Iakovlev <eyakovl@xxxxxxxxx>
> Signed-off-by: Siddharth Chandrasekaran <sidcha@xxxxxxxxx>
> ---
> arch/x86/kvm/hyperv.c | 147 +++++++++++++++++++++++-------------------
> 1 file changed, 79 insertions(+), 68 deletions(-)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index f98370a39936..8f6babd1ea0d 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1623,7 +1623,18 @@ static __always_inline unsigned long *sparse_set_to_vcpu_mask(
> return vcpu_bitmap;
> }
>
> -static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, u64 ingpa, u16 rep_cnt, bool ex)
> +struct kvm_hv_hcall {
> + u64 param;
> + u64 ingpa;
> + u64 outgpa;
> + u16 code;
> + u16 rep_cnt;
> + u16 rep_idx;
> + bool fast;
> + bool rep;
> +};
> +
> +static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool ex)

Nitpick: Would it make sense to also pack the fact that we're dealing
with a hypercall using ExProcessorMasks into 'struct kvm_hv_hcall' and
get rid of 'bool ex' parameter for both kvm_hv_flush_tlb() and
kvm_hv_send_ipi()? 'struct kvm_hv_hcall' is already a synthetic
aggregator for input and output so adding some other information there
may not be that big of a stretch...

> {
> struct kvm *kvm = vcpu->kvm;
> struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
> @@ -1638,7 +1649,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, u64 ingpa, u16 rep_cnt, bool
> bool all_cpus;
>
> if (!ex) {
> - if (unlikely(kvm_read_guest(kvm, ingpa, &flush, sizeof(flush))))
> + if (unlikely(kvm_read_guest(kvm, hc->ingpa, &flush, sizeof(flush))))
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
>
> trace_kvm_hv_flush_tlb(flush.processor_mask,
> @@ -1657,7 +1668,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, u64 ingpa, u16 rep_cnt, bool
> all_cpus = (flush.flags & HV_FLUSH_ALL_PROCESSORS) ||
> flush.processor_mask == 0;
> } else {
> - if (unlikely(kvm_read_guest(kvm, ingpa, &flush_ex,
> + if (unlikely(kvm_read_guest(kvm, hc->ingpa, &flush_ex,
> sizeof(flush_ex))))
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
>
> @@ -1679,8 +1690,8 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, u64 ingpa, u16 rep_cnt, bool
>
> if (!all_cpus &&
> kvm_read_guest(kvm,
> - ingpa + offsetof(struct hv_tlb_flush_ex,
> - hv_vp_set.bank_contents),
> + hc->ingpa + offsetof(struct hv_tlb_flush_ex,
> + hv_vp_set.bank_contents),
> sparse_banks,
> sparse_banks_len))
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
> @@ -1700,9 +1711,9 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, u64 ingpa, u16 rep_cnt, bool
> NULL, vcpu_mask, &hv_vcpu->tlb_flush);
>
> ret_success:
> - /* We always do full TLB flush, set rep_done = rep_cnt. */
> + /* We always do full TLB flush, set rep_done = hc->rep_cnt. */

Nitpicking: I'd suggest we word it a bit differently:

"We always do full TLB flush, set 'Reps completed' = 'Rep Count'."

so it matches TLFS rather than KVM internals.

> return (u64)HV_STATUS_SUCCESS |
> - ((u64)rep_cnt << HV_HYPERCALL_REP_COMP_OFFSET);
> + ((u64)hc->rep_cnt << HV_HYPERCALL_REP_COMP_OFFSET);
> }
>
> static void kvm_send_ipi_to_many(struct kvm *kvm, u32 vector,
> @@ -1724,8 +1735,7 @@ static void kvm_send_ipi_to_many(struct kvm *kvm, u32 vector,
> }
> }
>
> -static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, u64 ingpa, u64 outgpa,
> - bool ex, bool fast)
> +static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool ex)
> {
> struct kvm *kvm = vcpu->kvm;
> struct hv_send_ipi_ex send_ipi_ex;
> @@ -1740,25 +1750,25 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, u64 ingpa, u64 outgpa,
> bool all_cpus;
>
> if (!ex) {
> - if (!fast) {
> - if (unlikely(kvm_read_guest(kvm, ingpa, &send_ipi,
> + if (!hc->fast) {
> + if (unlikely(kvm_read_guest(kvm, hc->ingpa, &send_ipi,
> sizeof(send_ipi))))
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
> sparse_banks[0] = send_ipi.cpu_mask;
> vector = send_ipi.vector;
> } else {
> /* 'reserved' part of hv_send_ipi should be 0 */
> - if (unlikely(ingpa >> 32 != 0))
> + if (unlikely(hc->ingpa >> 32 != 0))
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
> - sparse_banks[0] = outgpa;
> - vector = (u32)ingpa;
> + sparse_banks[0] = hc->outgpa;
> + vector = (u32)hc->ingpa;
> }
> all_cpus = false;
> valid_bank_mask = BIT_ULL(0);
>
> trace_kvm_hv_send_ipi(vector, sparse_banks[0]);
> } else {
> - if (unlikely(kvm_read_guest(kvm, ingpa, &send_ipi_ex,
> + if (unlikely(kvm_read_guest(kvm, hc->ingpa, &send_ipi_ex,
> sizeof(send_ipi_ex))))
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
>
> @@ -1778,8 +1788,8 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, u64 ingpa, u64 outgpa,
>
> if (!all_cpus &&
> kvm_read_guest(kvm,
> - ingpa + offsetof(struct hv_send_ipi_ex,
> - vp_set.bank_contents),
> + hc->ingpa + offsetof(struct hv_send_ipi_ex,
> + vp_set.bank_contents),
> sparse_banks,
> sparse_banks_len))
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
> @@ -1839,20 +1849,21 @@ static int kvm_hv_hypercall_complete_userspace(struct kvm_vcpu *vcpu)
> return kvm_hv_hypercall_complete(vcpu, vcpu->run->hyperv.u.hcall.result);
> }
>
> -static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, bool fast, u64 param)
> +static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
> {
> struct kvm_hv *hv = to_kvm_hv(vcpu->kvm);
> struct eventfd_ctx *eventfd;
>
> - if (unlikely(!fast)) {
> + if (unlikely(!hc->fast)) {
> int ret;
> - gpa_t gpa = param;
> + gpa_t gpa = hc->ingpa;
>
> - if ((gpa & (__alignof__(param) - 1)) ||
> - offset_in_page(gpa) + sizeof(param) > PAGE_SIZE)
> + if ((gpa & (__alignof__(hc->ingpa) - 1)) ||
> + offset_in_page(gpa) + sizeof(hc->ingpa) > PAGE_SIZE)
> return HV_STATUS_INVALID_ALIGNMENT;
>
> - ret = kvm_vcpu_read_guest(vcpu, gpa, &param, sizeof(param));
> + ret = kvm_vcpu_read_guest(vcpu, gpa,
> + &hc->ingpa, sizeof(hc->ingpa));
> if (ret < 0)
> return HV_STATUS_INVALID_ALIGNMENT;
> }
> @@ -1862,15 +1873,15 @@ static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, bool fast, u64 param)
> * have no use for it, and in all known usecases it is zero, so just
> * report lookup failure if it isn't.
> */
> - if (param & 0xffff00000000ULL)
> + if (hc->ingpa & 0xffff00000000ULL)
> return HV_STATUS_INVALID_PORT_ID;
> /* remaining bits are reserved-zero */
> - if (param & ~KVM_HYPERV_CONN_ID_MASK)
> + if (hc->ingpa & ~KVM_HYPERV_CONN_ID_MASK)
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
>
> /* the eventfd is protected by vcpu->kvm->srcu, but conn_to_evt isn't */
> rcu_read_lock();
> - eventfd = idr_find(&hv->conn_to_evt, param);
> + eventfd = idr_find(&hv->conn_to_evt, hc->ingpa);
> rcu_read_unlock();
> if (!eventfd)
> return HV_STATUS_INVALID_PORT_ID;
> @@ -1881,9 +1892,8 @@ static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, bool fast, u64 param)
>
> int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
> {
> - u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
> - uint16_t code, rep_idx, rep_cnt;
> - bool fast, rep;
> + struct kvm_hv_hcall hc;
> + u64 ret = HV_STATUS_SUCCESS;
>
> /*
> * hypercall generates UD from non zero cpl and real mode
> @@ -1896,104 +1906,105 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>
> #ifdef CONFIG_X86_64
> if (is_64_bit_mode(vcpu)) {
> - param = kvm_rcx_read(vcpu);
> - ingpa = kvm_rdx_read(vcpu);
> - outgpa = kvm_r8_read(vcpu);
> + hc.param = kvm_rcx_read(vcpu);
> + hc.ingpa = kvm_rdx_read(vcpu);
> + hc.outgpa = kvm_r8_read(vcpu);
> } else
> #endif
> {
> - param = ((u64)kvm_rdx_read(vcpu) << 32) |
> - (kvm_rax_read(vcpu) & 0xffffffff);
> - ingpa = ((u64)kvm_rbx_read(vcpu) << 32) |
> - (kvm_rcx_read(vcpu) & 0xffffffff);
> - outgpa = ((u64)kvm_rdi_read(vcpu) << 32) |
> - (kvm_rsi_read(vcpu) & 0xffffffff);
> + hc.param = ((u64)kvm_rdx_read(vcpu) << 32) |
> + (kvm_rax_read(vcpu) & 0xffffffff);
> + hc.ingpa = ((u64)kvm_rbx_read(vcpu) << 32) |
> + (kvm_rcx_read(vcpu) & 0xffffffff);
> + hc.outgpa = ((u64)kvm_rdi_read(vcpu) << 32) |
> + (kvm_rsi_read(vcpu) & 0xffffffff);
> }
>
> - code = param & 0xffff;
> - fast = !!(param & HV_HYPERCALL_FAST_BIT);
> - rep_cnt = (param >> HV_HYPERCALL_REP_COMP_OFFSET) & 0xfff;
> - rep_idx = (param >> HV_HYPERCALL_REP_START_OFFSET) & 0xfff;
> - rep = !!(rep_cnt || rep_idx);
> + hc.code = hc.param & 0xffff;
> + hc.fast = !!(hc.param & HV_HYPERCALL_FAST_BIT);
> + hc.rep_cnt = (hc.param >> HV_HYPERCALL_REP_COMP_OFFSET) & 0xfff;
> + hc.rep_idx = (hc.param >> HV_HYPERCALL_REP_START_OFFSET) & 0xfff;
> + hc.rep = !!(hc.rep_cnt || hc.rep_idx);
>
> - trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
> + trace_kvm_hv_hypercall(hc.code, hc.fast, hc.rep_cnt, hc.rep_idx,
> + hc.ingpa, hc.outgpa);
>
> - switch (code) {
> + switch (hc.code) {
> case HVCALL_NOTIFY_LONG_SPIN_WAIT:
> - if (unlikely(rep)) {
> + if (unlikely(hc.rep)) {
> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
> break;
> }
> kvm_vcpu_on_spin(vcpu, true);
> break;
> case HVCALL_SIGNAL_EVENT:
> - if (unlikely(rep)) {
> + if (unlikely(hc.rep)) {
> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
> break;
> }
> - ret = kvm_hvcall_signal_event(vcpu, fast, ingpa);
> + ret = kvm_hvcall_signal_event(vcpu, &hc);
> if (ret != HV_STATUS_INVALID_PORT_ID)
> break;
> fallthrough; /* maybe userspace knows this conn_id */
> case HVCALL_POST_MESSAGE:
> /* don't bother userspace if it has no way to handle it */
> - if (unlikely(rep || !to_hv_synic(vcpu)->active)) {
> + if (unlikely(hc.rep || !to_hv_synic(vcpu)->active)) {
> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
> break;
> }
> vcpu->run->exit_reason = KVM_EXIT_HYPERV;
> vcpu->run->hyperv.type = KVM_EXIT_HYPERV_HCALL;
> - vcpu->run->hyperv.u.hcall.input = param;
> - vcpu->run->hyperv.u.hcall.params[0] = ingpa;
> - vcpu->run->hyperv.u.hcall.params[1] = outgpa;
> + vcpu->run->hyperv.u.hcall.input = hc.param;
> + vcpu->run->hyperv.u.hcall.params[0] = hc.ingpa;
> + vcpu->run->hyperv.u.hcall.params[1] = hc.outgpa;
> vcpu->arch.complete_userspace_io =
> kvm_hv_hypercall_complete_userspace;
> return 0;
> case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST:
> - if (unlikely(fast || !rep_cnt || rep_idx)) {
> + if (unlikely(hc.fast || !hc.rep_cnt || hc.rep_idx)) {
> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
> break;
> }
> - ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, false);
> + ret = kvm_hv_flush_tlb(vcpu, &hc, false);
> break;
> case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE:
> - if (unlikely(fast || rep)) {
> + if (unlikely(hc.fast || hc.rep)) {
> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
> break;
> }
> - ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, false);
> + ret = kvm_hv_flush_tlb(vcpu, &hc, false);
> break;
> case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX:
> - if (unlikely(fast || !rep_cnt || rep_idx)) {
> + if (unlikely(hc.fast || !hc.rep_cnt || hc.rep_idx)) {
> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
> break;
> }
> - ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, true);
> + ret = kvm_hv_flush_tlb(vcpu, &hc, true);
> break;
> case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX:
> - if (unlikely(fast || rep)) {
> + if (unlikely(hc.fast || hc.rep)) {
> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
> break;
> }
> - ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, true);
> + ret = kvm_hv_flush_tlb(vcpu, &hc, true);
> break;
> case HVCALL_SEND_IPI:
> - if (unlikely(rep)) {
> + if (unlikely(hc.rep)) {
> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
> break;
> }
> - ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, false, fast);
> + ret = kvm_hv_send_ipi(vcpu, &hc, false);
> break;
> case HVCALL_SEND_IPI_EX:
> - if (unlikely(fast || rep)) {
> + if (unlikely(hc.fast || hc.rep)) {
> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
> break;
> }
> - ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, true, false);
> + ret = kvm_hv_send_ipi(vcpu, &hc, true);
> break;
> case HVCALL_POST_DEBUG_DATA:
> case HVCALL_RETRIEVE_DEBUG_DATA:
> - if (unlikely(fast)) {
> + if (unlikely(hc.fast)) {
> ret = HV_STATUS_INVALID_PARAMETER;
> break;
> }
> @@ -2012,9 +2023,9 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
> }
> vcpu->run->exit_reason = KVM_EXIT_HYPERV;
> vcpu->run->hyperv.type = KVM_EXIT_HYPERV_HCALL;
> - vcpu->run->hyperv.u.hcall.input = param;
> - vcpu->run->hyperv.u.hcall.params[0] = ingpa;
> - vcpu->run->hyperv.u.hcall.params[1] = outgpa;
> + vcpu->run->hyperv.u.hcall.input = hc.param;
> + vcpu->run->hyperv.u.hcall.params[0] = hc.ingpa;
> + vcpu->run->hyperv.u.hcall.params[1] = hc.outgpa;
> vcpu->arch.complete_userspace_io =
> kvm_hv_hypercall_complete_userspace;
> return 0;

With or without the nitpicks from above addressed,

Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

--
Vitaly

Next message: Marco Elver: "Re: [PATCH v4 2/3] mm/slub, kunit: add a KUnit test for SLUB debugging functionality"
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In reply to: Siddharth Chandrasekaran: "[PATCH v2 2/4] KVM: hyper-v: Collect hypercall params into struct"
Next in thread: Siddharth Chandrasekaran: "Re: [PATCH v2 2/4] KVM: hyper-v: Collect hypercall params into struct"
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