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Message-ID: <2a3976ac-242b-260a-ce7b-2080d8e9d0f8@redhat.com>
Date: Thu, 25 Jun 2020 14:27:46 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
Sean Christopherson <sean.j.christopherson@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
the arch/x86 maintainers <x86@...nel.org>,
Tony W Wang-oc <TonyWWang-oc@...oxin.com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Pavel Machek <pavel@....cz>, "H. Peter Anvin" <hpa@...or.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux PM <linux-pm@...r.kernel.org>,
Brad Campbell <lists2009@...rfbargle.com>,
Liam Merwick <liam.merwick@...cle.com>,
Maxim Levitsky <mlevitsk@...hat.com>,
kvm-devel <kvm@...r.kernel.org>
Subject: Re: [PATCH v2] x86/cpu: Reinitialize IA32_FEAT_CTL MSR on BSP during
wakeup
On 25/06/20 14:06, Rafael J. Wysocki wrote:
> On Mon, Jun 8, 2020 at 7:49 PM Sean Christopherson
> <sean.j.christopherson@...el.com> wrote:
>>
>> Reinitialize IA32_FEAT_CTL on the BSP during wakeup to handle the case
>> where firmware doesn't initialize or save/restore across S3. This fixes
>> a bug where IA32_FEAT_CTL is left uninitialized and results in VMXON
>> taking a #GP due to VMX not being fully enabled, i.e. breaks KVM.
>>
>> Use init_ia32_feat_ctl() to "restore" IA32_FEAT_CTL as it already deals
>> with the case where the MSR is locked, and because APs already redo
>> init_ia32_feat_ctl() during suspend by virtue of the SMP boot flow being
>> used to reinitialize APs upon wakeup. Do the call in the early wakeup
>> flow to avoid dependencies in the syscore_ops chain, e.g. simply adding
>> a resume hook is not guaranteed to work, as KVM does VMXON in its own
>> resume hook, kvm_resume(), when KVM has active guests.
>>
>> Reported-by: Brad Campbell <lists2009@...rfbargle.com>
>> Tested-by: Brad Campbell <lists2009@...rfbargle.com>
>> Reviewed-by: Liam Merwick <liam.merwick@...cle.com>
>> Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
>> Cc: Paolo Bonzini <pbonzini@...hat.com>
>> Cc: kvm@...r.kernel.org
>> Cc: stable@...r.kernel.org # v5.6
>> Fixes: 21bd3467a58e ("KVM: VMX: Drop initialization of IA32_FEAT_CTL MSR")
>> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
>
> Given the regression fix nature of this patch, is it being taken care
> of by anyone (tip in particular) already?
I was waiting for tip to pick it up, but I can as well with an Acked-by
(KVM is broken by the patch but there's nothing KVM specific in it).
Paolo
>> ---
>>
>> v2:
>> - Collect Reviewed/Tested tags. [Brad, Liam, Maxim].
>> - Include asm/cpu.h to fix Zhaoxin and Centaur builds. [Brad, LKP]
>> - Add Cc to stable. [Liam]
>>
>> arch/x86/include/asm/cpu.h | 5 +++++
>> arch/x86/kernel/cpu/centaur.c | 1 +
>> arch/x86/kernel/cpu/cpu.h | 4 ----
>> arch/x86/kernel/cpu/zhaoxin.c | 1 +
>> arch/x86/power/cpu.c | 6 ++++++
>> 5 files changed, 13 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
>> index dd17c2da1af5..da78ccbd493b 100644
>> --- a/arch/x86/include/asm/cpu.h
>> +++ b/arch/x86/include/asm/cpu.h
>> @@ -58,4 +58,9 @@ static inline bool handle_guest_split_lock(unsigned long ip)
>> return false;
>> }
>> #endif
>> +#ifdef CONFIG_IA32_FEAT_CTL
>> +void init_ia32_feat_ctl(struct cpuinfo_x86 *c);
>> +#else
>> +static inline void init_ia32_feat_ctl(struct cpuinfo_x86 *c) {}
>> +#endif
>> #endif /* _ASM_X86_CPU_H */
>> diff --git a/arch/x86/kernel/cpu/centaur.c b/arch/x86/kernel/cpu/centaur.c
>> index 426792565d86..c5cf336e5077 100644
>> --- a/arch/x86/kernel/cpu/centaur.c
>> +++ b/arch/x86/kernel/cpu/centaur.c
>> @@ -3,6 +3,7 @@
>> #include <linux/sched.h>
>> #include <linux/sched/clock.h>
>>
>> +#include <asm/cpu.h>
>> #include <asm/cpufeature.h>
>> #include <asm/e820/api.h>
>> #include <asm/mtrr.h>
>> diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h
>> index 37fdefd14f28..38ab6e115eac 100644
>> --- a/arch/x86/kernel/cpu/cpu.h
>> +++ b/arch/x86/kernel/cpu/cpu.h
>> @@ -80,8 +80,4 @@ extern void x86_spec_ctrl_setup_ap(void);
>>
>> extern u64 x86_read_arch_cap_msr(void);
>>
>> -#ifdef CONFIG_IA32_FEAT_CTL
>> -void init_ia32_feat_ctl(struct cpuinfo_x86 *c);
>> -#endif
>> -
>> #endif /* ARCH_X86_CPU_H */
>> diff --git a/arch/x86/kernel/cpu/zhaoxin.c b/arch/x86/kernel/cpu/zhaoxin.c
>> index df1358ba622b..05fa4ef63490 100644
>> --- a/arch/x86/kernel/cpu/zhaoxin.c
>> +++ b/arch/x86/kernel/cpu/zhaoxin.c
>> @@ -2,6 +2,7 @@
>> #include <linux/sched.h>
>> #include <linux/sched/clock.h>
>>
>> +#include <asm/cpu.h>
>> #include <asm/cpufeature.h>
>>
>> #include "cpu.h"
>> diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
>> index aaff9ed7ff45..b0d3c5ca6d80 100644
>> --- a/arch/x86/power/cpu.c
>> +++ b/arch/x86/power/cpu.c
>> @@ -193,6 +193,8 @@ static void fix_processor_context(void)
>> */
>> static void notrace __restore_processor_state(struct saved_context *ctxt)
>> {
>> + struct cpuinfo_x86 *c;
>> +
>> if (ctxt->misc_enable_saved)
>> wrmsrl(MSR_IA32_MISC_ENABLE, ctxt->misc_enable);
>> /*
>> @@ -263,6 +265,10 @@ static void notrace __restore_processor_state(struct saved_context *ctxt)
>> mtrr_bp_restore();
>> perf_restore_debug_store();
>> msr_restore_context(ctxt);
>> +
>> + c = &cpu_data(smp_processor_id());
>> + if (cpu_has(c, X86_FEATURE_MSR_IA32_FEAT_CTL))
>> + init_ia32_feat_ctl(c);
>> }
>>
>> /* Needed by apm.c */
>> --
>> 2.26.0
>>
>
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