On 08.11.23 13:11, Vitaly Kuznetsov wrote:
Alexander Graf <graf@xxxxxxxxxx> writes:
On 08.11.23 12:17, Nicolas Saenz Julienne wrote:
Prepare infrastructure to be able to return data through the XMM
registers when Hyper-V hypercalls are issues in fast mode. The XMM
registers are exposed to user-space through KVM_EXIT_HYPERV_HCALL and
restored on successful hypercall completion.
Signed-off-by: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx>
---
arch/x86/include/asm/hyperv-tlfs.h | 2 +-
arch/x86/kvm/hyperv.c | 33 +++++++++++++++++++++++++++++-
include/uapi/linux/kvm.h | 6 ++++++
3 files changed, 39 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 2ff26f53cd62..af594aa65307 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -49,7 +49,7 @@
/* Support for physical CPU dynamic partitioning events is available*/
#define HV_X64_CPU_DYNAMIC_PARTITIONING_AVAILABLE BIT(3)
/*
- * Support for passing hypercall input parameter block via XMM
+ * Support for passing hypercall input and output parameter block via XMM
* registers is available
*/
#define HV_X64_HYPERCALL_XMM_INPUT_AVAILABLE BIT(4)
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 238afd7335e4..e1bc861ab3b0 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1815,6 +1815,7 @@ struct kvm_hv_hcall {
u16 rep_idx;
bool fast;
bool rep;
+ bool xmm_dirty;
sse128_t xmm[HV_HYPERCALL_MAX_XMM_REGISTERS];
/*
@@ -2346,9 +2347,33 @@ static int kvm_hv_hypercall_complete(struct kvm_vcpu *vcpu, u64 result)
return ret;
}
+static void kvm_hv_write_xmm(struct kvm_hyperv_xmm_reg *xmm)
+{
+ int reg;
+
+ kvm_fpu_get();
+ for (reg = 0; reg < HV_HYPERCALL_MAX_XMM_REGISTERS; reg++) {
+ const sse128_t data = sse128(xmm[reg].low, xmm[reg].high);
+ _kvm_write_sse_reg(reg, &data);
+ }
+ kvm_fpu_put();
+}
+
+static bool kvm_hv_is_xmm_output_hcall(u16 code)
+{
+ return false;
+}
+
static int kvm_hv_hypercall_complete_userspace(struct kvm_vcpu *vcpu)
{
- return kvm_hv_hypercall_complete(vcpu, vcpu->run->hyperv.u.hcall.result);
+ bool fast = !!(vcpu->run->hyperv.u.hcall.input & HV_HYPERCALL_FAST_BIT);
+ u16 code = vcpu->run->hyperv.u.hcall.input & 0xffff;
+ u64 result = vcpu->run->hyperv.u.hcall.result;
+
+ if (kvm_hv_is_xmm_output_hcall(code) && hv_result_success(result) && fast)
+ kvm_hv_write_xmm(vcpu->run->hyperv.u.hcall.xmm);
+
+ return kvm_hv_hypercall_complete(vcpu, result);
}
static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
@@ -2623,6 +2648,9 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
break;
}
+ if ((ret & HV_HYPERCALL_RESULT_MASK) == HV_STATUS_SUCCESS && hc.xmm_dirty)
+ kvm_hv_write_xmm((struct kvm_hyperv_xmm_reg*)hc.xmm);
+
hypercall_complete:
return kvm_hv_hypercall_complete(vcpu, ret);
@@ -2632,6 +2660,8 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
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;
+ if (hc.fast)
+ memcpy(vcpu->run->hyperv.u.hcall.xmm, hc.xmm, sizeof(hc.xmm));
vcpu->arch.complete_userspace_io = kvm_hv_hypercall_complete_userspace;
return 0;
}
@@ -2780,6 +2810,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
ent->ebx |= HV_ENABLE_EXTENDED_HYPERCALLS;
ent->edx |= HV_X64_HYPERCALL_XMM_INPUT_AVAILABLE;
+ ent->edx |= HV_X64_HYPERCALL_XMM_OUTPUT_AVAILABLE;
Shouldn't this be guarded by an ENABLE_CAP to make sure old user space
that doesn't know about xmm outputs is still able to run with newer kernels?
No, we don't do CAPs for new Hyper-V features anymore since we have
KVM_GET_SUPPORTED_HV_CPUID. Userspace is not supposed to simply copy
its output into guest visible CPUIDs, it must only enable features it
knows. Even 'hv_passthrough' option in QEMU doesn't pass unknown
features through.
Ah, nice :). That simplifies things.
Alex
Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879
