From: Andy Lutomirski <luto@amacapital.net>
To: Bandan Das <bsd@redhat.com>
Cc: Maxim Levitsky <mlevitsk@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wei Huang <wei.huang2@amd.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
pbonzini@redhat.com, seanjc@google.com, joro@8bytes.org,
bp@alien8.de, tglx@linutronix.de, mingo@redhat.com,
x86@kernel.org, jmattson@google.com, wanpengli@tencent.com,
dgilbert@redhat.com
Subject: Re: [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by VM instructions
Date: Tue, 12 Jan 2021 07:51:19 -0800 [thread overview]
Message-ID: <8FAC639B-5EC6-42EE-B886-33AEF3CD5E26@amacapital.net> (raw)
In-Reply-To: <jpgturmgnu6.fsf@linux.bootlegged.copy>
> On Jan 12, 2021, at 7:46 AM, Bandan Das <bsd@redhat.com> wrote:
>
> Andy Lutomirski <luto@amacapital.net> writes:
> ...
>>>>>> #endif diff --git a/arch/x86/kvm/mmu/mmu.c
>>>>>> b/arch/x86/kvm/mmu/mmu.c index 6d16481aa29d..c5c4aaf01a1a 100644
>>>>>> --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@
>>>>>> -50,6 +50,7 @@ #include <asm/io.h> #include <asm/vmx.h> #include
>>>>>> <asm/kvm_page_track.h> +#include <asm/e820/api.h> #include
>>>>>> "trace.h"
>>>>>>
>>>>>> extern bool itlb_multihit_kvm_mitigation; @@ -5675,6 +5676,12 @@
>>>>>> void kvm_mmu_slot_set_dirty(struct kvm *kvm, }
>>>>>> EXPORT_SYMBOL_GPL(kvm_mmu_slot_set_dirty);
>>>>>>
>>>>>> +bool kvm_is_host_reserved_region(u64 gpa) +{ + return
>>>>>> e820__mbapped_raw_any(gpa-1, gpa+1, E820_TYPE_RESERVED); +}
>>>>> While _e820__mapped_any()'s doc says '.. checks if any part of
>>>>> the range <start,end> is mapped ..' it seems to me that the real
>>>>> check is [start, end) so we should use 'gpa' instead of 'gpa-1',
>>>>> no?
>>>> Why do you need to check GPA at all?
>>>>
>>> To reduce the scope of the workaround.
>>>
>>> The errata only happens when you use one of SVM instructions in the
>>> guest with EAX that happens to be inside one of the host reserved
>>> memory regions (for example SMM).
>>
>> This code reduces the scope of the workaround at the cost of
>> increasing the complexity of the workaround and adding a nonsensical
>> coupling between KVM and host details and adding an export that really
>> doesn’t deserve to be exported.
>>
>> Is there an actual concrete benefit to this check?
>
> Besides reducing the scope, my intention for the check was that we should
> know if such exceptions occur for any other undiscovered reasons with other
> memory types rather than hiding them under this workaround.
Ask AMD?
I would also believe that someone somewhere has a firmware that simply omits the problematic region instead of listing it as reserved.
>
> Bandan
>
>
>
next prev parent reply other threads:[~2021-01-12 15:52 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-12 6:37 [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by VM instructions Wei Huang
2021-01-12 6:37 ` [PATCH 2/2] KVM: SVM: Add support for VMCB address check change Wei Huang
2021-01-12 19:18 ` Sean Christopherson
2021-01-14 11:39 ` Maxim Levitsky
2021-01-14 12:04 ` Maxim Levitsky
2021-01-12 11:09 ` [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by VM instructions Maxim Levitsky
2021-01-12 21:05 ` Wei Huang
2021-01-12 12:15 ` Vitaly Kuznetsov
2021-01-12 15:11 ` Andy Lutomirski
2021-01-12 15:17 ` Maxim Levitsky
2021-01-12 15:22 ` Andy Lutomirski
2021-01-12 15:46 ` Bandan Das
2021-01-12 15:51 ` Andy Lutomirski [this message]
2021-01-12 17:56 ` Sean Christopherson
2021-01-13 4:55 ` Wei Huang
2021-01-12 21:50 ` Wei Huang
2021-01-12 14:01 ` Paolo Bonzini
2021-01-12 17:42 ` Sean Christopherson
2021-01-13 12:35 ` Paolo Bonzini
2021-01-15 7:00 ` Wei Huang
2021-01-17 18:20 ` Paolo Bonzini
2021-01-12 17:36 ` Sean Christopherson
2021-01-12 17:59 ` Sean Christopherson
2021-01-12 18:58 ` Andy Lutomirski
2021-01-13 5:15 ` Wei Huang
2021-01-14 11:42 ` Maxim Levitsky
2021-01-13 5:03 ` Wei Huang
2021-01-13 12:40 ` Paolo Bonzini
2021-01-12 19:40 ` Sean Christopherson
2021-01-12 20:00 ` Bandan Das
2021-01-14 11:47 ` Maxim Levitsky
2021-01-14 17:19 ` Sean Christopherson
2021-01-14 11:55 ` Maxim Levitsky
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