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From: Sean Christopherson <seanjc@google.com>
To: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Cc: kvm@vger.kernel.org, pbonzini@redhat.com, jmattson@google.com
Subject: Re: [PATCH 3/7 v7] KVM: nSVM: No need to set bits 11:0 in MSRPM and IOPM bitmaps
Date: Tue, 20 Apr 2021 20:00:51 +0000	[thread overview]
Message-ID: <YH8y86iPBdTwMT18@google.com> (raw)
In-Reply-To: <20210412215611.110095-4-krish.sadhukhan@oracle.com>

On Mon, Apr 12, 2021, Krish Sadhukhan wrote:
> According to APM vol 2, hardware ignores the low 12 bits in MSRPM and IOPM
> bitmaps. Therefore setting/unssetting these bits has no effect as far as
> VMRUN is concerned. Also, setting/unsetting these bits prevents tests from
> verifying hardware behavior.
> 
> Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> ---
>  arch/x86/kvm/svm/nested.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index ae53ae46ebca..fd42c8b7f99a 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -287,8 +287,6 @@ static void nested_load_control_from_vmcb12(struct vcpu_svm *svm,
>  
>  	/* Copy it here because nested_svm_check_controls will check it.  */
>  	svm->nested.ctl.asid           = control->asid;
> -	svm->nested.ctl.msrpm_base_pa &= ~0x0fffULL;
> -	svm->nested.ctl.iopm_base_pa  &= ~0x0fffULL;

This will break nested_svm_vmrun_msrpm() if L1 passes an unaligned address.
The shortlog is also wrong, KVM isn't setting bits, it's clearing bits.

I also don't think svm->nested.ctl.msrpm_base_pa makes its way to hardware; IIUC,
it's a copy of vmcs12->control.msrpm_base_pa.  The bitmap that gets loaded into
the "real" VMCB is vmcb02->control.msrpm_base_pa.

>  }
>  
>  /*
> -- 
> 2.27.0
> 

  parent reply	other threads:[~2021-04-20 20:00 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-12 21:56 [PATCH 0/7 v7] KVM: nSVM: Check addresses of MSR bitmap and IO bitmap tables on vmrun of nested guests Krish Sadhukhan
2021-04-12 21:56 ` [PATCH 1/7 v7] KVM: SVM: Define actual size of IOPM and MSRPM tables Krish Sadhukhan
2021-04-12 21:56 ` [PATCH 2/7 v7] KVM: nSVM: Define an exit code to reflect consistency check failure Krish Sadhukhan
2021-04-17 14:17   ` Paolo Bonzini
2021-04-19 17:57     ` Krish Sadhukhan
2021-04-19 18:28       ` Paolo Bonzini
2021-04-19 18:36         ` Jim Mattson
2021-04-12 21:56 ` [PATCH 3/7 v7] KVM: nSVM: No need to set bits 11:0 in MSRPM and IOPM bitmaps Krish Sadhukhan
2021-04-17 14:18   ` Paolo Bonzini
2021-04-20 20:00   ` Sean Christopherson [this message]
2021-04-22 17:50     ` Krish Sadhukhan
2021-04-22 17:52       ` Krish Sadhukhan
2021-04-22 17:56       ` Krish Sadhukhan
2021-04-22 18:01         ` Sean Christopherson
2021-04-23  1:12           ` Krish Sadhukhan
2021-04-23 15:56             ` Sean Christopherson
2021-04-23 20:31               ` Paolo Bonzini
2021-04-26 21:59                 ` Krish Sadhukhan
2021-04-26 22:07                   ` Sean Christopherson
2021-04-12 21:56 ` [PATCH 4/7 v7] nSVM: Check addresses of MSR and IO permission maps Krish Sadhukhan
2021-04-12 21:56 ` [PATCH 5/7 v7] SVM: Use ALIGN macro when aligning 'io_bitmap_area' Krish Sadhukhan
2021-04-12 21:56 ` [PATCH 6/7 v7] nSVM: Define an exit code to reflect consistency check failure Krish Sadhukhan
2021-04-12 21:56 ` [PATCH 7/7 v7] nSVM: Test addresses of MSR and IO permissions maps Krish Sadhukhan
2021-04-17 14:35 ` [PATCH 0/7 v7] KVM: nSVM: Check addresses of MSR bitmap and IO bitmap tables on vmrun of nested guests Paolo Bonzini

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