[PATCH v2 0/4] Restrict PV features to only enabled guests

[PATCH v2 0/4] Restrict PV features to only enabled guests

[Oliver Upton]

To date, KVM has allowed guests to use paravirtual interfaces regardless
of the configured CPUID. While almost any guest will consult the
KVM_CPUID_FEATURES leaf _before_ using PV features, it is still
undesirable to have such interfaces silently present.

This series aims to address the issue by adding explicit checks against
the guest's CPUID when servicing any paravirtual feature. Since this
effectively changes the guest/hypervisor ABI, a KVM_CAP is warranted to
guard the new behavior.

Patches 1-2 refactor some of the PV code in anticipation of the change.
Patch 3 introduces the checks + KVM_CAP. Finally, patch 4 fixes some doc
typos that were noticed when working on this series.

v1 => v2:
 - Strip Change-Id footers (checkpatch is your friend!)

Parent commit: f3633c268354 ("Merge tag 'kvm-s390-next-5.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into kvm-next-5.6")

Oliver Upton (4):
  kvm: x86: encapsulate wrmsr(MSR_KVM_SYSTEM_TIME) emulation in helper
    fn
  kvm: x86: set wall_clock in kvm_write_wall_clock()
  kvm: x86: only provide PV features if enabled in guest's CPUID
  Documentation: kvm: fix some typos in cpuid.rst

 Documentation/virt/kvm/api.rst   |  11 +++
 Documentation/virt/kvm/cpuid.rst |  88 +++++++++++-----------
 arch/x86/include/asm/kvm_host.h  |   6 ++
 arch/x86/kvm/cpuid.h             |  16 ++++
 arch/x86/kvm/x86.c               | 122 +++++++++++++++++++++++--------
 include/uapi/linux/kvm.h         |   1 +
 6 files changed, 171 insertions(+), 73 deletions(-)

-- 
2.28.0.236.gb10cc79966-goog

[PATCH v2 1/4] kvm: x86: encapsulate wrmsr(MSR_KVM_SYSTEM_TIME) emulation in helper fn

[Oliver Upton]

No functional change intended.

Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
---
 arch/x86/kvm/x86.c | 58 +++++++++++++++++++++++++---------------------
 1 file changed, 32 insertions(+), 26 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dc4370394ab8..d18582aefa9f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1822,6 +1822,34 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
 	kvm_write_guest(kvm, wall_clock, &version, sizeof(version));
 }
 
+void kvm_write_system_time(struct kvm_vcpu *vcpu, gpa_t system_time,
+			   bool old_msr, bool host_initiated)
+{
+	struct kvm_arch *ka = &vcpu->kvm->arch;
+
+	if (vcpu->vcpu_id == 0 && !host_initiated) {
+		if (ka->boot_vcpu_runs_old_kvmclock && old_msr)
+			kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
+
+		ka->boot_vcpu_runs_old_kvmclock = old_msr;
+	}
+
+	vcpu->arch.time = system_time;
+	kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu);
+
+	/* we verify if the enable bit is set... */
+	vcpu->arch.pv_time_enabled = false;
+	if (!(system_time & 1))
+		return;
+
+	if (!kvm_gfn_to_hva_cache_init(vcpu->kvm,
+				       &vcpu->arch.pv_time, system_time & ~1ULL,
+				       sizeof(struct pvclock_vcpu_time_info)))
+		vcpu->arch.pv_time_enabled = true;
+
+	return;
+}
+
 static uint32_t div_frac(uint32_t dividend, uint32_t divisor)
 {
 	do_shl32_div32(dividend, divisor);
@@ -2973,33 +3001,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		kvm_write_wall_clock(vcpu->kvm, data);
 		break;
 	case MSR_KVM_SYSTEM_TIME_NEW:
-	case MSR_KVM_SYSTEM_TIME: {
-		struct kvm_arch *ka = &vcpu->kvm->arch;
-
-		if (vcpu->vcpu_id == 0 && !msr_info->host_initiated) {
-			bool tmp = (msr == MSR_KVM_SYSTEM_TIME);
-
-			if (ka->boot_vcpu_runs_old_kvmclock != tmp)
-				kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
-
-			ka->boot_vcpu_runs_old_kvmclock = tmp;
-		}
-
-		vcpu->arch.time = data;
-		kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu);
-
-		/* we verify if the enable bit is set... */
-		vcpu->arch.pv_time_enabled = false;
-		if (!(data & 1))
-			break;
-
-		if (!kvm_gfn_to_hva_cache_init(vcpu->kvm,
-		     &vcpu->arch.pv_time, data & ~1ULL,
-		     sizeof(struct pvclock_vcpu_time_info)))
-			vcpu->arch.pv_time_enabled = true;
-
+		kvm_write_system_time(vcpu, data, false, msr_info->host_initiated);
+		break;
+	case MSR_KVM_SYSTEM_TIME:
+		kvm_write_system_time(vcpu, data, true, msr_info->host_initiated);
 		break;
-	}
 	case MSR_KVM_ASYNC_PF_EN:
 		if (kvm_pv_enable_async_pf(vcpu, data))
 			return 1;
-- 
2.28.0.236.gb10cc79966-goog

[PATCH v2 2/4] kvm: x86: set wall_clock in kvm_write_wall_clock()

[Oliver Upton]

Small change to avoid meaningless duplication in the subsequent patch.
No functional change intended.

Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
---
 arch/x86/kvm/x86.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d18582aefa9f..53d3a5ffde9c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1790,6 +1790,8 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
 	struct pvclock_wall_clock wc;
 	u64 wall_nsec;
 
+	kvm->arch.wall_clock = wall_clock;
+
 	if (!wall_clock)
 		return;
 
@@ -2997,7 +2999,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		break;
 	case MSR_KVM_WALL_CLOCK_NEW:
 	case MSR_KVM_WALL_CLOCK:
-		vcpu->kvm->arch.wall_clock = data;
 		kvm_write_wall_clock(vcpu->kvm, data);
 		break;
 	case MSR_KVM_SYSTEM_TIME_NEW:
-- 
2.28.0.236.gb10cc79966-goog

[PATCH v2 3/4] kvm: x86: only provide PV features if enabled in guest's CPUID

[Oliver Upton]

KVM unconditionally provides PV features to the guest, regardless of the
configured CPUID. An unwitting guest that doesn't check
KVM_CPUID_FEATURES before use could access paravirt features that
userspace did not intend to provide. Fix this by checking the guest's
CPUID before performing any paravirtual operations.

Introduce a capability, KVM_CAP_ENFORCE_PV_FEATURE_CPUID, to gate the
aforementioned enforcement. Migrating a VM from a host w/o this patch to
a host with this patch could silently change the ABI exposed to the
guest, warranting that we default to the old behavior and opt-in for
the new one.

Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
---
 Documentation/virt/kvm/api.rst  | 11 ++++++
 arch/x86/include/asm/kvm_host.h |  6 +++
 arch/x86/kvm/cpuid.h            | 16 ++++++++
 arch/x86/kvm/x86.c              | 67 ++++++++++++++++++++++++++++++---
 include/uapi/linux/kvm.h        |  1 +
 5 files changed, 96 insertions(+), 5 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 644e5326aa50..e8fc6e34f344 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6155,3 +6155,14 @@ KVM can therefore start protected VMs.
 This capability governs the KVM_S390_PV_COMMAND ioctl and the
 KVM_MP_STATE_LOAD MP_STATE. KVM_SET_MP_STATE can fail for protected
 guests when the state change is invalid.
+
+
+8.24 KVM_CAP_ENFORCE_PV_CPUID
+-----------------------------
+
+Architectures: x86
+
+When enabled, KVM will disable paravirtual features provided to the
+guest according to the bits in the KVM_CPUID_FEATURES CPUID leaf
+(0x40000001). Otherwise, a guest may use the paravirtual features
+regardless of what has actually been exposed through the CPUID leaf.
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5ab3af7275d8..a641c3840a1e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -788,6 +788,12 @@ struct kvm_vcpu_arch {
 
 	/* AMD MSRC001_0015 Hardware Configuration */
 	u64 msr_hwcr;
+
+	/*
+	 * Indicates whether PV emulation should be disabled if not present in
+	 * the guest's cpuid.
+	 */
+	bool enforce_pv_feature_cpuid;
 };
 
 struct kvm_lpage_info {
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index 3a923ae15f2f..c364c2877583 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -5,6 +5,7 @@
 #include "x86.h"
 #include <asm/cpu.h>
 #include <asm/processor.h>
+#include <uapi/asm/kvm_para.h>
 
 extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
 void kvm_set_cpu_caps(void);
@@ -308,4 +309,19 @@ static inline bool page_address_valid(struct kvm_vcpu *vcpu, gpa_t gpa)
 	return PAGE_ALIGNED(gpa) && !(gpa >> cpuid_maxphyaddr(vcpu));
 }
 
+static __always_inline bool guest_pv_has(struct kvm_vcpu *vcpu,
+					   unsigned int kvm_feature)
+{
+	struct kvm_cpuid_entry2 *cpuid;
+
+	if (!vcpu->arch.enforce_pv_feature_cpuid)
+		return true;
+
+	cpuid = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
+	if (!cpuid)
+		return false;
+
+	return cpuid->eax & (1u << kvm_feature);
+}
+
 #endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 53d3a5ffde9c..51a9e8e394a5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2763,6 +2763,14 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
 	if (data & 0x30)
 		return 1;
 
+	if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_VMEXIT) &&
+	    (data & KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT))
+		return 1;
+
+	if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT) &&
+	    (data & KVM_ASYNC_PF_DELIVERY_AS_INT))
+		return 1;
+
 	if (!lapic_in_kernel(vcpu))
 		return 1;
 
@@ -2840,10 +2848,12 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 	 * Doing a TLB flush here, on the guest's behalf, can avoid
 	 * expensive IPIs.
 	 */
-	trace_kvm_pv_tlb_flush(vcpu->vcpu_id,
-		st->preempted & KVM_VCPU_FLUSH_TLB);
-	if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB)
-		kvm_vcpu_flush_tlb_guest(vcpu);
+	if (guest_pv_has(vcpu, KVM_FEATURE_PV_TLB_FLUSH)) {
+		trace_kvm_pv_tlb_flush(vcpu->vcpu_id,
+				       st->preempted & KVM_VCPU_FLUSH_TLB);
+		if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB)
+			kvm_vcpu_flush_tlb_guest(vcpu);
+	}
 
 	vcpu->arch.st.preempted = 0;
 
@@ -2998,30 +3008,54 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vcpu->arch.smi_count = data;
 		break;
 	case MSR_KVM_WALL_CLOCK_NEW:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2))
+			return 1;
+
+		kvm_write_wall_clock(vcpu->kvm, data);
+		break;
 	case MSR_KVM_WALL_CLOCK:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE))
+			return 1;
+
 		kvm_write_wall_clock(vcpu->kvm, data);
 		break;
 	case MSR_KVM_SYSTEM_TIME_NEW:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2))
+			return 1;
+
 		kvm_write_system_time(vcpu, data, false, msr_info->host_initiated);
 		break;
 	case MSR_KVM_SYSTEM_TIME:
-		kvm_write_system_time(vcpu, data, true, msr_info->host_initiated);
+		if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE))
+			return 1;
+
+		kvm_write_system_time(vcpu, data, true,  msr_info->host_initiated);
 		break;
 	case MSR_KVM_ASYNC_PF_EN:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
+			return 1;
+
 		if (kvm_pv_enable_async_pf(vcpu, data))
 			return 1;
 		break;
 	case MSR_KVM_ASYNC_PF_INT:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
+			return 1;
+
 		if (kvm_pv_enable_async_pf_int(vcpu, data))
 			return 1;
 		break;
 	case MSR_KVM_ASYNC_PF_ACK:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
+			return 1;
 		if (data & 0x1) {
 			vcpu->arch.apf.pageready_pending = false;
 			kvm_check_async_pf_completion(vcpu);
 		}
 		break;
 	case MSR_KVM_STEAL_TIME:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_STEAL_TIME))
+			return 1;
 
 		if (unlikely(!sched_info_on()))
 			return 1;
@@ -3038,11 +3072,17 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 
 		break;
 	case MSR_KVM_PV_EOI_EN:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_PV_EOI))
+			return 1;
+
 		if (kvm_lapic_enable_pv_eoi(vcpu, data, sizeof(u8)))
 			return 1;
 		break;
 
 	case MSR_KVM_POLL_CONTROL:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_POLL_CONTROL))
+			return 1;
+
 		/* only enable bit supported */
 		if (data & (-1ULL << 1))
 			return 1;
@@ -3522,6 +3562,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_EXCEPTION_PAYLOAD:
 	case KVM_CAP_SET_GUEST_DEBUG:
 	case KVM_CAP_LAST_CPU:
+	case KVM_CAP_ENFORCE_PV_FEATURE_CPUID:
 		r = 1;
 		break;
 	case KVM_CAP_SYNC_REGS:
@@ -4389,6 +4430,11 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 
 		return kvm_x86_ops.enable_direct_tlbflush(vcpu);
 
+	case KVM_CAP_ENFORCE_PV_FEATURE_CPUID:
+		vcpu->arch.enforce_pv_feature_cpuid = cap->args[0];
+
+		return 0;
+
 	default:
 		return -EINVAL;
 	}
@@ -7723,11 +7769,16 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 		goto out;
 	}
 
+	ret = -KVM_ENOSYS;
+
 	switch (nr) {
 	case KVM_HC_VAPIC_POLL_IRQ:
 		ret = 0;
 		break;
 	case KVM_HC_KICK_CPU:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_PV_UNHALT))
+			break;
+
 		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
 		kvm_sched_yield(vcpu->kvm, a1);
 		ret = 0;
@@ -7738,9 +7789,15 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 		break;
 #endif
 	case KVM_HC_SEND_IPI:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_PV_SEND_IPI))
+			break;
+
 		ret = kvm_pv_send_ipi(vcpu->kvm, a0, a1, a2, a3, op_64_bit);
 		break;
 	case KVM_HC_SCHED_YIELD:
+		if (!guest_pv_has(vcpu, KVM_FEATURE_PV_SCHED_YIELD))
+			break;
+
 		kvm_sched_yield(vcpu->kvm, a0);
 		ret = 0;
 		break;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index f6d86033c4fa..48c2d5c10b1e 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1035,6 +1035,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_LAST_CPU 184
 #define KVM_CAP_SMALLER_MAXPHYADDR 185
 #define KVM_CAP_S390_DIAG318 186
+#define KVM_CAP_ENFORCE_PV_FEATURE_CPUID 187
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.28.0.236.gb10cc79966-goog

[PATCH v2 4/4] Documentation: kvm: fix some typos in cpuid.rst

[Oliver Upton]

Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
---
 Documentation/virt/kvm/cpuid.rst | 88 ++++++++++++++++----------------
 1 file changed, 44 insertions(+), 44 deletions(-)

diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
index a7dff9186bed..f1583e682cc8 100644
--- a/Documentation/virt/kvm/cpuid.rst
+++ b/Documentation/virt/kvm/cpuid.rst
@@ -38,64 +38,64 @@ returns::
 
 where ``flag`` is defined as below:
 
-================================= =========== ================================
-flag                              value       meaning
-================================= =========== ================================
-KVM_FEATURE_CLOCKSOURCE           0           kvmclock available at msrs
-                                              0x11 and 0x12
+================================== =========== ================================
+flag                               value       meaning
+================================== =========== ================================
+KVM_FEATURE_CLOCKSOURCE            0           kvmclock available at msrs
+                                               0x11 and 0x12
 
-KVM_FEATURE_NOP_IO_DELAY          1           not necessary to perform delays
-                                              on PIO operations
+KVM_FEATURE_NOP_IO_DELAY           1           not necessary to perform delays
+                                               on PIO operations
 
-KVM_FEATURE_MMU_OP                2           deprecated
+KVM_FEATURE_MMU_OP                 2           deprecated
 
-KVM_FEATURE_CLOCKSOURCE2          3           kvmclock available at msrs
-                                              0x4b564d00 and 0x4b564d01
+KVM_FEATURE_CLOCKSOURCE2           3           kvmclock available at msrs
+                                               0x4b564d00 and 0x4b564d01
 
-KVM_FEATURE_ASYNC_PF              4           async pf can be enabled by
-                                              writing to msr 0x4b564d02
+KVM_FEATURE_ASYNC_PF               4           async pf can be enabled by
+                                               writing to msr 0x4b564d02
 
-KVM_FEATURE_STEAL_TIME            5           steal time can be enabled by
-                                              writing to msr 0x4b564d03
+KVM_FEATURE_STEAL_TIME             5           steal time can be enabled by
+                                               writing to msr 0x4b564d03
 
-KVM_FEATURE_PV_EOI                6           paravirtualized end of interrupt
-                                              handler can be enabled by
-                                              writing to msr 0x4b564d04
+KVM_FEATURE_PV_EOI                 6           paravirtualized end of interrupt
+                                               handler can be enabled by
+                                               writing to msr 0x4b564d04
 
-KVM_FEATURE_PV_UNHAULT            7           guest checks this feature bit
-                                              before enabling paravirtualized
-                                              spinlock support
+KVM_FEATURE_PV_UNHALT              7           guest checks this feature bit
+                                               before enabling paravirtualized
+                                               spinlock support
 
-KVM_FEATURE_PV_TLB_FLUSH          9           guest checks this feature bit
-                                              before enabling paravirtualized
-                                              tlb flush
+KVM_FEATURE_PV_TLB_FLUSH           9           guest checks this feature bit
+                                               before enabling paravirtualized
+                                               tlb flush
 
-KVM_FEATURE_ASYNC_PF_VMEXIT       10          paravirtualized async PF VM EXIT
-                                              can be enabled by setting bit 2
-                                              when writing to msr 0x4b564d02
+KVM_FEATURE_ASYNC_PF_VMEXIT        10          paravirtualized async PF VM EXIT
+                                               can be enabled by setting bit 2
+                                               when writing to msr 0x4b564d02
 
-KVM_FEATURE_PV_SEND_IPI           11          guest checks this feature bit
-                                              before enabling paravirtualized
-                                              sebd IPIs
+KVM_FEATURE_PV_SEND_IPI            11          guest checks this feature bit
+                                               before enabling paravirtualized
+                                               send IPIs
 
-KVM_FEATURE_PV_POLL_CONTROL       12          host-side polling on HLT can
-                                              be disabled by writing
-                                              to msr 0x4b564d05.
+KVM_FEATURE_PV_POLL_CONTROL        12          host-side polling on HLT can
+                                               be disabled by writing
+                                               to msr 0x4b564d05.
 
-KVM_FEATURE_PV_SCHED_YIELD        13          guest checks this feature bit
-                                              before using paravirtualized
-                                              sched yield.
+KVM_FEATURE_PV_SCHED_YIELD         13          guest checks this feature bit
+                                               before using paravirtualized
+                                               sched yield.
 
-KVM_FEATURE_ASYNC_PF_INT          14          guest checks this feature bit
-                                              before using the second async
-                                              pf control msr 0x4b564d06 and
-                                              async pf acknowledgment msr
-                                              0x4b564d07.
+KVM_FEATURE_ASYNC_PF_INT           14          guest checks this feature bit
+                                               before using the second async
+                                               pf control msr 0x4b564d06 and
+                                               async pf acknowledgment msr
+                                               0x4b564d07.
 
-KVM_FEATURE_CLOCSOURCE_STABLE_BIT 24          host will warn if no guest-side
-                                              per-cpu warps are expeced in
-                                              kvmclock
-================================= =========== ================================
+KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24          host will warn if no guest-side
+                                               per-cpu warps are expected in
+                                               kvmclock
+================================== =========== ================================
 
 ::
 
-- 
2.28.0.236.gb10cc79966-goog

Re: [PATCH v2 1/4] kvm: x86: encapsulate wrmsr(MSR_KVM_SYSTEM_TIME) emulation in helper fn

[kernel test robot]

[-- Attachment #1: Type: text/plain, Size: 2338 bytes --]

Hi Oliver,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on kvm/linux-next]
[also build test WARNING on vhost/linux-next v5.8 next-20200805]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Oliver-Upton/Restrict-PV-features-to-only-enabled-guests/20200806-052304
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next
config: x86_64-allyesconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce (this is a W=1 build):
        # save the attached .config to linux build tree
        make W=1 ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> arch/x86/kvm/x86.c:1825:6: warning: no previous prototype for 'kvm_write_system_time' [-Wmissing-prototypes]
    1825 | void kvm_write_system_time(struct kvm_vcpu *vcpu, gpa_t system_time,
         |      ^~~~~~~~~~~~~~~~~~~~~

vim +/kvm_write_system_time +1825 arch/x86/kvm/x86.c

  1824	
> 1825	void kvm_write_system_time(struct kvm_vcpu *vcpu, gpa_t system_time,
  1826				   bool old_msr, bool host_initiated)
  1827	{
  1828		struct kvm_arch *ka = &vcpu->kvm->arch;
  1829	
  1830		if (vcpu->vcpu_id == 0 && !host_initiated) {
  1831			if (ka->boot_vcpu_runs_old_kvmclock && old_msr)
  1832				kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
  1833	
  1834			ka->boot_vcpu_runs_old_kvmclock = old_msr;
  1835		}
  1836	
  1837		vcpu->arch.time = system_time;
  1838		kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu);
  1839	
  1840		/* we verify if the enable bit is set... */
  1841		vcpu->arch.pv_time_enabled = false;
  1842		if (!(system_time & 1))
  1843			return;
  1844	
  1845		if (!kvm_gfn_to_hva_cache_init(vcpu->kvm,
  1846					       &vcpu->arch.pv_time, system_time & ~1ULL,
  1847					       sizeof(struct pvclock_vcpu_time_info)))
  1848			vcpu->arch.pv_time_enabled = true;
  1849	
  1850		return;
  1851	}
  1852	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

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