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From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Ben Gardon <bgardon@google.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Junaid Shahid <junaids@google.com>
Subject: Re: [PATCH v2 1/3] KVM: x86: assign two bits to track SPTE kinds
Date: Thu, 12 Dec 2019 01:33:45 +0100	[thread overview]
Message-ID: <5c39ee9b-3b58-f1c9-889d-6e012bbbac6c@redhat.com> (raw)
In-Reply-To: <20191212002902.GM5044@linux.intel.com>

On 12/12/19 01:29, Sean Christopherson wrote:
>>   */
>> -#define MMIO_SPTE_GEN_MASK		GENMASK_ULL(18, 0)
>> +#define MMIO_SPTE_GEN_MASK		GENMASK_ULL(17, 0)
>>  
>>  #define MMIO_SPTE_GEN_LOW_START		3
>>  #define MMIO_SPTE_GEN_LOW_END		11
>>  #define MMIO_SPTE_GEN_LOW_MASK		GENMASK_ULL(MMIO_SPTE_GEN_LOW_END, \
>>  						    MMIO_SPTE_GEN_LOW_START)
>>  
>> -#define MMIO_SPTE_GEN_HIGH_START	52
>> -#define MMIO_SPTE_GEN_HIGH_END		61
>> +/* Leave room for SPTE_SPECIAL_MASK.  */
>> +#define MMIO_SPTE_GEN_HIGH_START	PT64_SECOND_AVAIL_BITS_SHIFT
> I'd rather have GEN_HIGH_START be an explicit bit number and then add
> a BUILD_BUG_ON(GEN_HIGH_START < PT64_SECOND_AVAIL_BITS_SHIFT) to ensure
> the MMIO gen doesn't overlap other stuff.  That way we get a build error
> if someone changes PT64_SECOND_AVAIL_BITS_SHIFT, otherwise the MMIO gen
> will end up who knows where and probably overwrite NX or EPT.SUPPRESS_VE.
> 

Fair enough.  While at it I'll also add MMIO_SPTE_GEN_BITS (
	MMIO_SPTE_GEN_LOW_END - MMIO_SPTE_GEN_LOW_START + 1
	+ MMIO_SPTE_GEN_HIGH_END - MMIO_SPTE_GEN_HIGH_START + 1) and use it in
MMIO_SPTE_GEN_MASK.

Paolo


  reply	other threads:[~2019-12-12  0:33 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-27 11:15 [PATCH v2 0/3] KVM: MMU: fix nested guest live migration with PML Paolo Bonzini
2019-09-27 11:15 ` [PATCH v2 1/3] KVM: x86: assign two bits to track SPTE kinds Paolo Bonzini
2019-12-11 18:39   ` Ben Gardon
2019-12-11 19:13     ` Sean Christopherson
2019-12-11 23:28       ` Paolo Bonzini
2019-12-12  0:29         ` Sean Christopherson
2019-12-12  0:33           ` Paolo Bonzini [this message]
2019-09-27 11:15 ` [PATCH v2 2/3] KVM: x86: fix nested guest live migration with PML Paolo Bonzini
2019-09-27 20:24   ` Junaid Shahid
2019-09-27 11:15 ` [PATCH v2 3/3] selftests: kvm: add test for dirty logging inside nested guests Paolo Bonzini

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