[PATCH v2 2/8] KVM: x86: Get the number of Hyper-V sparse banks from the VARHEAD field

Sean Christopherson
2021-10-30T00:08:26Z

Get the number of sparse banks from the VARHEAD field, which the guest is
required to provide as "The size of a variable header, in QWORDS.", where
the variable header is:

Variable Header Bytes = {Total Header Bytes - sizeof(Fixed Header)}
rounded up to nearest multiple of 8
Variable HeaderSize = Variable Header Bytes / 8

In other words, the VARHEAD should match the number of sparse banks.
Keep the manual count as a sanity check, but otherwise rely on the field
so as to more closely align with the logic defined in the TLFS and to
allow for future cleanups.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/hyperv.c | 35 ++++++++++++++++++-------------
arch/x86/kvm/trace.h | 14 +++++++------
include/asm-generic/hyperv-tlfs.h | 1 +
3 files changed, 30 insertions(+), 20 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 814d1a1f2cb8..cf18aa1712bf 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1742,6 +1742,7 @@ struct kvm_hv_hcall {
u64 ingpa;
u64 outgpa;
u16 code;
+ u16 var_cnt;
u16 rep_cnt;
u16 rep_idx;
bool fast;
@@ -1761,7 +1762,6 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool
unsigned long *vcpu_mask;
u64 valid_bank_mask;
u64 sparse_banks[64];
- int sparse_banks_len;
bool all_cpus;

if (!ex) {
@@ -1811,24 +1811,28 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool
all_cpus = flush_ex.hv_vp_set.format !=
HV_GENERIC_SET_SPARSE_4K;

- sparse_banks_len = bitmap_weight((unsigned long *)&valid_bank_mask, 64);
+ if (hc->var_cnt != bitmap_weight((unsigned long *)&valid_bank_mask, 64))
+ return HV_STATUS_INVALID_HYPERCALL_INPUT;

- if (!sparse_banks_len && !all_cpus)
+ if (!hc->var_cnt && !all_cpus)
goto ret_success;

if (!all_cpus) {
if (hc->fast) {
- if (sparse_banks_len > HV_HYPERCALL_MAX_XMM_REGISTERS - 1)
+ if (hc->var_cnt > HV_HYPERCALL_MAX_XMM_REGISTERS - 1)
return HV_STATUS_INVALID_HYPERCALL_INPUT;
- for (i = 0; i < sparse_banks_len; i += 2) {
+ for (i = 0; i < hc->var_cnt; i += 2) {
sparse_banks[i] = sse128_lo(hc->xmm[i / 2 + 1]);
sparse_banks[i + 1] = sse128_hi(hc->xmm[i / 2 + 1]);
}
} else {
+ if (hc->var_cnt > 64)
+ return HV_STATUS_INVALID_HYPERCALL_INPUT;
+
gpa = hc->ingpa + offsetof(struct hv_tlb_flush_ex,
hv_vp_set.bank_contents);
if (unlikely(kvm_read_guest(kvm, gpa, sparse_banks,
- sparse_banks_len *
+ hc->var_cnt *
sizeof(sparse_banks[0]))))
return HV_STATUS_INVALID_HYPERCALL_INPUT;
}
@@ -1884,7 +1888,6 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool
unsigned long *vcpu_mask;
unsigned long valid_bank_mask;
u64 sparse_banks[64];
- int sparse_banks_len;
u32 vector;
bool all_cpus;

@@ -1917,22 +1920,25 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool

vector = send_ipi_ex.vector;
valid_bank_mask = send_ipi_ex.vp_set.valid_bank_mask;
- sparse_banks_len = bitmap_weight(&valid_bank_mask, 64) *
- sizeof(sparse_banks[0]);
-
all_cpus = send_ipi_ex.vp_set.format == HV_GENERIC_SET_ALL;

+ if (hc->var_cnt != bitmap_weight(&valid_bank_mask, 64))
+ return HV_STATUS_INVALID_HYPERCALL_INPUT;
+
if (all_cpus)
goto check_and_send_ipi;

- if (!sparse_banks_len)
+ if (!hc->var_cnt)
goto ret_success;

+ if (hc->var_cnt > 64)
+ return HV_STATUS_INVALID_HYPERCALL_INPUT;
+
if (kvm_read_guest(kvm,
hc->ingpa + offsetof(struct hv_send_ipi_ex,
vp_set.bank_contents),
sparse_banks,
- sparse_banks_len))
+ hc->var_cnt * sizeof(sparse_banks[0])))
return HV_STATUS_INVALID_HYPERCALL_INPUT;
}

@@ -2190,13 +2196,14 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
}

hc.code = hc.param & 0xffff;
+ hc.var_cnt = (hc.param & HV_HYPERCALL_VARHEAD_MASK) >> HV_HYPERCALL_VARHEAD_OFFSET;
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(hc.code, hc.fast, hc.rep_cnt, hc.rep_idx,
- hc.ingpa, hc.outgpa);
+ trace_kvm_hv_hypercall(hc.code, hc.fast, hc.var_cnt, hc.rep_cnt,
+ hc.rep_idx, hc.ingpa, hc.outgpa);

if (unlikely(!hv_check_hypercall_access(hv_vcpu, hc.code))) {
ret = HV_STATUS_ACCESS_DENIED;
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 953b0fcb21ee..f6625cfb686c 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -64,9 +64,9 @@ TRACE_EVENT(kvm_hypercall,
* Tracepoint for hypercall.
*/
TRACE_EVENT(kvm_hv_hypercall,
- TP_PROTO(__u16 code, bool fast, __u16 rep_cnt, __u16 rep_idx,
- __u64 ingpa, __u64 outgpa),
- TP_ARGS(code, fast, rep_cnt, rep_idx, ingpa, outgpa),
+ TP_PROTO(__u16 code, bool fast, __u16 var_cnt, __u16 rep_cnt,
+ __u16 rep_idx, __u64 ingpa, __u64 outgpa),
+ TP_ARGS(code, fast, var_cnt, rep_cnt, rep_idx, ingpa, outgpa),

TP_STRUCT__entry(
__field( __u16, rep_cnt )
@@ -74,6 +74,7 @@ TRACE_EVENT(kvm_hv_hypercall,
__field( __u64, ingpa )
__field( __u64, outgpa )
__field( __u16, code )
+ __field( __u16, var_cnt )
__field( bool, fast )
),

@@ -83,13 +84,14 @@ TRACE_EVENT(kvm_hv_hypercall,
__entry->ingpa = ingpa;
__entry->outgpa = outgpa;
__entry->code = code;
+ __entry->var_cnt = var_cnt;
__entry->fast = fast;
),

- TP_printk("code 0x%x %s cnt 0x%x idx 0x%x in 0x%llx out 0x%llx",
+ TP_printk("code 0x%x %s var_cnt 0x%x cnt 0x%x idx 0x%x in 0x%llx out 0x%llx",
__entry->code, __entry->fast ? "fast" : "slow",
- __entry->rep_cnt, __entry->rep_idx, __entry->ingpa,
- __entry->outgpa)
+ __entry->var_cnt, __entry->rep_cnt, __entry->rep_idx,
+ __entry->ingpa, __entry->outgpa)
);

TRACE_EVENT(kvm_hv_hypercall_done,
diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index 56348a541c50..1ba8e6da4427 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -182,6 +182,7 @@ enum HV_GENERIC_SET_FORMAT {
#define HV_HYPERCALL_RESULT_MASK GENMASK_ULL(15, 0)
#define HV_HYPERCALL_FAST_BIT BIT(16)
#define HV_HYPERCALL_VARHEAD_OFFSET 17
+#define HV_HYPERCALL_VARHEAD_MASK GENMASK_ULL(26, 17)
#define HV_HYPERCALL_REP_COMP_OFFSET 32
#define HV_HYPERCALL_REP_COMP_1 BIT_ULL(32)
#define HV_HYPERCALL_REP_COMP_MASK GENMASK_ULL(43, 32)
--
2.33.1.1089.g2158813163f-goog