This is a note to let you know that I've just added the patch titled
KVM: x86: fix backward migration with async_PF
to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-fix-backward-migration-with-async_pf.patch
and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From fe2a3027e74e40a3ece3a4c1e4e51403090a907a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@xxxxxxxxxx>
Date: Thu, 1 Feb 2018 22:16:21 +0100
Subject: KVM: x86: fix backward migration with async_PF
MIME-Version: 1.0
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From: Radim Krčmář <rkrcmar@xxxxxxxxxx>
commit fe2a3027e74e40a3ece3a4c1e4e51403090a907a upstream.
Guests on new hypersiors might set KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT
bit when enabling async_PF, but this bit is reserved on old hypervisors,
which results in a failure upon migration.
To avoid breaking different cases, we are checking for CPUID feature bit
before enabling the feature and nothing else.
Fixes: 52a5c155cf79 ("KVM: async_pf: Let guest support delivery of async_pf from guest mode")
Cc: <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
[jwang: port to 4.14]
Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/virtual/kvm/cpuid.txt | 4 ++++
Documentation/virtual/kvm/msr.txt | 3 ++-
arch/x86/include/uapi/asm/kvm_para.h | 1 +
arch/x86/kernel/kvm.c | 8 ++++----
arch/x86/kvm/cpuid.c | 3 ++-
5 files changed, 13 insertions(+), 6 deletions(-)
--- a/Documentation/virtual/kvm/cpuid.txt
+++ b/Documentation/virtual/kvm/cpuid.txt
@@ -54,6 +54,10 @@ KVM_FEATURE_PV_UNHALT ||
|| || before enabling paravirtualized
|| || spinlock support.
------------------------------------------------------------------------------
+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_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side
|| || per-cpu warps are expected in
|| || kvmclock.
--- a/Documentation/virtual/kvm/msr.txt
+++ b/Documentation/virtual/kvm/msr.txt
@@ -170,7 +170,8 @@ MSR_KVM_ASYNC_PF_EN: 0x4b564d02
when asynchronous page faults are enabled on the vcpu 0 when
disabled. Bit 1 is 1 if asynchronous page faults can be injected
when vcpu is in cpl == 0. Bit 2 is 1 if asynchronous page faults
- are delivered to L1 as #PF vmexits.
+ are delivered to L1 as #PF vmexits. Bit 2 can be set only if
+ KVM_FEATURE_ASYNC_PF_VMEXIT is present in CPUID.
First 4 byte of 64 byte memory location will be written to by
the hypervisor at the time of asynchronous page fault (APF)
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -25,6 +25,7 @@
#define KVM_FEATURE_STEAL_TIME 5
#define KVM_FEATURE_PV_EOI 6
#define KVM_FEATURE_PV_UNHALT 7
+#define KVM_FEATURE_ASYNC_PF_VMEXIT 10
/* The last 8 bits are used to indicate how to interpret the flags field
* in pvclock structure. If no bits are set, all flags are ignored.
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -341,10 +341,10 @@ static void kvm_guest_cpu_init(void)
#endif
pa |= KVM_ASYNC_PF_ENABLED;
- /* Async page fault support for L1 hypervisor is optional */
- if (wrmsr_safe(MSR_KVM_ASYNC_PF_EN,
- (pa | KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT) & 0xffffffff, pa >> 32) < 0)
- wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
+ if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT))
+ pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
+
+ wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
__this_cpu_write(apf_reason.enabled, 1);
printk(KERN_INFO"KVM setup async PF for cpu %d\n",
smp_processor_id());
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -597,7 +597,8 @@ static inline int __do_cpuid_ent(struct
(1 << KVM_FEATURE_ASYNC_PF) |
(1 << KVM_FEATURE_PV_EOI) |
(1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
- (1 << KVM_FEATURE_PV_UNHALT);
+ (1 << KVM_FEATURE_PV_UNHALT) |
+ (1 << KVM_FEATURE_ASYNC_PF_VMEXIT);
if (sched_info_on())
entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
Patches currently in stable-queue which might be from rkrcmar@xxxxxxxxxx are
queue-4.15/kvm-x86-fix-backward-migration-with-async_pf.patch