From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:42606 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751106AbeCIOoA (ORCPT ); Fri, 9 Mar 2018 09:44:00 -0500 Subject: Re: [stable-4.14/4.15] KVM: x86: fix backward migration with async_PF To: Jack Wang , stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <1520601621-8728-1-git-send-email-jinpu.wangl@profitbricks.com> From: Paolo Bonzini Message-ID: <2ad7637d-cbcd-657e-6d6a-833d29797f37@redhat.com> Date: Fri, 9 Mar 2018 15:43:58 +0100 MIME-Version: 1.0 In-Reply-To: <1520601621-8728-1-git-send-email-jinpu.wangl@profitbricks.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: On 09/03/2018 14:20, Jack Wang wrote: > From: Radim Krčmář > > 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: > Reviewed-by: Wanpeng Li > Reviewed-by: David Hildenbrand > Signed-off-by: Radim Krčmář > Signed-off-by: Paolo Bonzini > [jwang: port to 4.14] > Signed-off-by: Jack Wang > --- > 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(-) > > diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt > index 3c65feb..a81c97a 100644 > --- a/Documentation/virtual/kvm/cpuid.txt > +++ b/Documentation/virtual/kvm/cpuid.txt > @@ -54,6 +54,10 @@ KVM_FEATURE_PV_UNHALT || 7 || guest checks this feature bit > || || 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. > diff --git a/Documentation/virtual/kvm/msr.txt b/Documentation/virtual/kvm/msr.txt > index 1ebecc1..f3f0d57 100644 > --- 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) > diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h > index 09cc064..989db88 100644 > --- 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. > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index b40ffbf..0a93e83b 100644 > --- 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()); > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 13f5d42..4f544f2 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -597,7 +597,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > (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); > Acked-by: Paolo Bonzini Thanks Jack! Paolo