[PATCH 04/18] KVM: x86: hyper-v: Introduce VTL awareness to Hyper-V's PV-IPIs

Nicolas Saenz Julienne
2024-06-09T15:52:44Z

HvCallSendSyntheticClusterIpi and HvCallSendSyntheticClusterIpiEx allow
sending VTL-aware IPIs. Honour the hcall by exiting to user-space upon
receiving a request with a valid VTL target. This behaviour is only
available if the VSM CPUID flag is available and exposed to the guest.
It doesn't introduce a behaviour change otherwise.

User-space is accountable for the correct processing of the PV-IPI
before resuming execution.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
---
arch/x86/kvm/hyperv.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 42f44546fe79c..d00baf3ffb165 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2217,16 +2217,20 @@ static void kvm_hv_send_ipi_to_many(struct kvm *kvm, u32 vector,

static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
{
+ bool vsm_enabled = kvm_hv_cpuid_vsm_enabled(vcpu);
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
u64 *sparse_banks = hv_vcpu->sparse_banks;
struct kvm *kvm = vcpu->kvm;
struct hv_send_ipi_ex send_ipi_ex;
struct hv_send_ipi send_ipi;
+ union hv_input_vtl *in_vtl;
u64 valid_bank_mask;
+ int rsvd_shift;
u32 vector;
bool all_cpus;

if (hc->code == HVCALL_SEND_IPI) {
+ in_vtl = &send_ipi.in_vtl;
if (!hc->fast) {
if (unlikely(kvm_read_guest(kvm, hc->ingpa, &send_ipi,
sizeof(send_ipi))))
@@ -2235,16 +2239,22 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
vector = send_ipi.vector;
} else {
/* 'reserved' part of hv_send_ipi should be 0 */
- if (unlikely(hc->ingpa >> 32 != 0))
+ rsvd_shift = vsm_enabled ? 40 : 32;
+ if (unlikely(hc->ingpa >> rsvd_shift != 0))
return HV_STATUS_INVALID_HYPERCALL_INPUT;
+ in_vtl->as_uint8 = (u8)(hc->ingpa >> 32);
sparse_banks[0] = hc->outgpa;
vector = (u32)hc->ingpa;
}
all_cpus = false;
valid_bank_mask = BIT_ULL(0);

+ if (in_vtl->use_target_vtl)
+ return -ENODEV;
+
trace_kvm_hv_send_ipi(vector, sparse_banks[0]);
} else {
+ in_vtl = &send_ipi_ex.in_vtl;
if (!hc->fast) {
if (unlikely(kvm_read_guest(kvm, hc->ingpa, &send_ipi_ex,
sizeof(send_ipi_ex))))
@@ -2253,8 +2263,12 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
send_ipi_ex.vector = (u32)hc->ingpa;
send_ipi_ex.vp_set.format = hc->outgpa;
send_ipi_ex.vp_set.valid_bank_mask = sse128_lo(hc->xmm[0]);
+ in_vtl->as_uint8 = (u8)(hc->ingpa >> 32);
}

+ if (vsm_enabled && in_vtl->use_target_vtl)
+ return -ENODEV;
+
trace_kvm_hv_send_ipi_ex(send_ipi_ex.vector,
send_ipi_ex.vp_set.format,
send_ipi_ex.vp_set.valid_bank_mask);
@@ -2682,6 +2696,9 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
break;
}
ret = kvm_hv_send_ipi(vcpu, &hc);
+ /* VTL-enabled ipi, let user-space handle it */
+ if (ret == -ENODEV)
+ goto hypercall_userspace_exit;
break;
case HVCALL_POST_DEBUG_DATA:
case HVCALL_RETRIEVE_DEBUG_DATA:
--
2.40.1