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From: Thomas Tai <thomas.tai@oracle.com>
To: Marc Zyngier <maz@kernel.org>
Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] KVM: arm64: Fixes ARM VM hangs at boot
Date: Thu, 1 Oct 2020 08:59:54 -0400	[thread overview]
Message-ID: <b5d6692e-c6cd-4183-9bae-d59b8ec7392d@oracle.com> (raw)
In-Reply-To: <f906ecd23609bbdf4a1db991624943d5@kernel.org>



On 2020-10-01 4:30 a.m., Marc Zyngier wrote:
> Hi Thomas,
> 
> On 2020-09-30 23:12, Thomas Tai wrote:
>> When using the latest kernel v5.9-rc7 on an ARM server, VMs could
>> hang at boot with no output. The commit a0e50aa3f4a8 removed
>> asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)),
>> it looks like isb is still needed for non
>> ARM64_WORKAROUND_SPECULATIVE_AT host when switching to guest.
> 
> Is that on an eMAG system, by any chance?

Hi Marc,
Yes, it is indeed an eMAG system.

> 
>>
>> The code fragment for the original patch:
>> -       /* __load_guest_stage2() includes an ISB for the workaround. */
>> -       __load_guest_stage2(kvm);
>> -       asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
>> +       __load_guest_stage2(mmu);
>>
>> The code should have been:
>> -       /* __load_guest_stage2() includes an ISB for the workaround. */
>> -       __load_guest_stage2(kvm);
>> -       asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
>> +       __load_guest_stage2(mmu);
>> +       asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
>> ie, the workaround is still needed.
>>
>> Fixes: a0e50aa3f4a8 ("KVM: arm64: Factor out stage 2 page table data from
>> struct kvm")
>>
>> Signed-off-by: Thomas Tai <thomas.tai@oracle.com>
>> ---
>>  arch/arm64/kvm/hyp/nvhe/tlb.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c 
>> b/arch/arm64/kvm/hyp/nvhe/tlb.c
>> index 69eae60..536496e 100644
>> --- a/arch/arm64/kvm/hyp/nvhe/tlb.c
>> +++ b/arch/arm64/kvm/hyp/nvhe/tlb.c
>> @@ -32,6 +32,7 @@ static void __tlb_switch_to_guest(struct kvm_s2_mmu 
>> *mmu,
>>      }
>>
>>      __load_guest_stage2(mmu);
>> +    asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
>>  }
>>
>>  static void __tlb_switch_to_host(struct tlb_inv_context *cxt)
> 
> Ouch. I remember fixing this a while ago, but somehow dropped it
> after applying it and *not* merging it...
> 
> Thanks a lot for the heads up!
> 
>          M.
> 
> [1] 
> https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm64/pre-nv-5.9 

Good to know you have the fix.

Thank you,
Thomas

> 
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Thomas Tai <thomas.tai@oracle.com>
To: Marc Zyngier <maz@kernel.org>
Cc: kvmarm@lists.cs.columbia.edu, james.morse@arm.com,
	linux-arm-kernel@lists.infradead.org,
	julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com
Subject: Re: [PATCH] KVM: arm64: Fixes ARM VM hangs at boot
Date: Thu, 1 Oct 2020 08:59:54 -0400	[thread overview]
Message-ID: <b5d6692e-c6cd-4183-9bae-d59b8ec7392d@oracle.com> (raw)
In-Reply-To: <f906ecd23609bbdf4a1db991624943d5@kernel.org>



On 2020-10-01 4:30 a.m., Marc Zyngier wrote:
> Hi Thomas,
> 
> On 2020-09-30 23:12, Thomas Tai wrote:
>> When using the latest kernel v5.9-rc7 on an ARM server, VMs could
>> hang at boot with no output. The commit a0e50aa3f4a8 removed
>> asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)),
>> it looks like isb is still needed for non
>> ARM64_WORKAROUND_SPECULATIVE_AT host when switching to guest.
> 
> Is that on an eMAG system, by any chance?

Hi Marc,
Yes, it is indeed an eMAG system.

> 
>>
>> The code fragment for the original patch:
>> -       /* __load_guest_stage2() includes an ISB for the workaround. */
>> -       __load_guest_stage2(kvm);
>> -       asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
>> +       __load_guest_stage2(mmu);
>>
>> The code should have been:
>> -       /* __load_guest_stage2() includes an ISB for the workaround. */
>> -       __load_guest_stage2(kvm);
>> -       asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
>> +       __load_guest_stage2(mmu);
>> +       asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
>> ie, the workaround is still needed.
>>
>> Fixes: a0e50aa3f4a8 ("KVM: arm64: Factor out stage 2 page table data from
>> struct kvm")
>>
>> Signed-off-by: Thomas Tai <thomas.tai@oracle.com>
>> ---
>>  arch/arm64/kvm/hyp/nvhe/tlb.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c 
>> b/arch/arm64/kvm/hyp/nvhe/tlb.c
>> index 69eae60..536496e 100644
>> --- a/arch/arm64/kvm/hyp/nvhe/tlb.c
>> +++ b/arch/arm64/kvm/hyp/nvhe/tlb.c
>> @@ -32,6 +32,7 @@ static void __tlb_switch_to_guest(struct kvm_s2_mmu 
>> *mmu,
>>      }
>>
>>      __load_guest_stage2(mmu);
>> +    asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
>>  }
>>
>>  static void __tlb_switch_to_host(struct tlb_inv_context *cxt)
> 
> Ouch. I remember fixing this a while ago, but somehow dropped it
> after applying it and *not* merging it...
> 
> Thanks a lot for the heads up!
> 
>          M.
> 
> [1] 
> https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm64/pre-nv-5.9 

Good to know you have the fix.

Thank you,
Thomas

> 

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-10-01 14:38 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-30 22:12 [PATCH] KVM: arm64: Fixes ARM VM hangs at boot Thomas Tai
2020-09-30 22:12 ` Thomas Tai
2020-10-01  8:30 ` Marc Zyngier
2020-10-01  8:30   ` Marc Zyngier
2020-10-01 12:59   ` Thomas Tai [this message]
2020-10-01 12:59     ` Thomas Tai

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