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From: Paolo Bonzini <pbonzini@redhat.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	KarimAllah Ahmed <karahmed@amazon.de>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, rkrcmar@redhat.com
Subject: Re: [PATCH v5 04/13] KVM: Introduce a new guest mapping API
Date: Wed, 30 Jan 2019 18:08:56 +0100	[thread overview]
Message-ID: <6e3f4c34-72c0-2abe-91b9-6c06ea86785d@redhat.com> (raw)
In-Reply-To: <20190123175014.GK19289@Konrads-MacBook-Pro.local>

On 23/01/19 18:50, Konrad Rzeszutek Wilk wrote:
>> +	if (dirty)
>> +		kvm_release_pfn_dirty(map->pfn);
>> +	else
>> +		kvm_release_pfn_clean(map->pfn);
>> +	map->hva = NULL;
> I keep on having this gnawing feeling that we MUST set map->page to
> NULL.
> 
> That is I can see how it is not needed if you are using 'map' and
> 'unmap' together - for that we are good. But what I am worried is that
> some one unmaps it .. and instead of checking map->hva they end up
> checking map->page and think the page is mapped.

I think that would break anyway the memremap case.

So I think we should indeed reset map->page, but we should set it to a
poison value:

#define KVM_UNMAPPED_PAGE    ((void *) 0x500 + POISON_POINTER_DELTA)

mem->page = KVM_UNMAPPED_PAGE;

This should make it clear to everyone that checking map->page is _not_
the right thing to do in any case.

Paolo

> Would you be OK adding that extra statement just as a fail-safe
> mechanism in case someones misues the APIs?


  parent reply	other threads:[~2019-01-30 17:09 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09  9:42 [PATCH v5 00/13] KVM/X86: Introduce a new guest mapping interface KarimAllah Ahmed
2019-01-09  9:42 ` [PATCH v5 01/13] X86/nVMX: handle_vmon: Read 4 bytes from guest memory KarimAllah Ahmed
2019-01-23 16:59   ` Konrad Rzeszutek Wilk
2019-01-09  9:42 ` [PATCH v5 02/13] X86/nVMX: Update the PML table without mapping and unmapping the page KarimAllah Ahmed
2019-01-23 17:17   ` Konrad Rzeszutek Wilk
2019-01-09  9:42 ` [PATCH v5 03/13] X86/KVM: Handle PFNs outside of kernel reach when touching GPTEs KarimAllah Ahmed
2019-01-23 17:31   ` Konrad Rzeszutek Wilk
2019-01-09  9:42 ` [PATCH v5 04/13] KVM: Introduce a new guest mapping API KarimAllah Ahmed
2019-01-10 13:07   ` David Hildenbrand
2019-01-25 18:01     ` Raslan, KarimAllah
2019-01-23 17:41   ` Konrad Rzeszutek Wilk
2019-01-23 17:50   ` Konrad Rzeszutek Wilk
2019-01-25 18:09     ` Raslan, KarimAllah
2019-01-30 17:08     ` Paolo Bonzini [this message]
2019-01-09  9:42 ` [PATCH v5 05/13] X86/nVMX: handle_vmptrld: Use kvm_vcpu_map when copying VMCS12 from guest memory KarimAllah Ahmed
2019-01-23 17:44   ` Konrad Rzeszutek Wilk
2019-01-09  9:42 ` [PATCH v5 06/13] KVM/nVMX: Use kvm_vcpu_map when mapping the L1 MSR bitmap KarimAllah Ahmed
2019-01-09  9:42 ` [PATCH v5 07/13] KVM/nVMX: Use kvm_vcpu_map when mapping the virtual APIC page KarimAllah Ahmed
2019-01-23 17:57   ` Konrad Rzeszutek Wilk
2019-01-25 18:14     ` Raslan, KarimAllah
2019-01-09  9:42 ` [PATCH v5 08/13] KVM/nVMX: Use kvm_vcpu_map when mapping the posted interrupt descriptor table KarimAllah Ahmed
2019-01-23 18:03   ` Konrad Rzeszutek Wilk
2019-01-25 18:15     ` Raslan, KarimAllah
2019-01-09  9:42 ` [PATCH v5 09/13] KVM/X86: Use kvm_vcpu_map in emulator_cmpxchg_emulated KarimAllah Ahmed
2019-01-23 18:04   ` Konrad Rzeszutek Wilk
2019-01-09  9:42 ` [PATCH v5 10/13] KVM/nSVM: Use the new mapping API for mapping guest memory KarimAllah Ahmed
2019-01-23 18:08   ` Konrad Rzeszutek Wilk
2019-01-09  9:42 ` [PATCH v5 11/13] KVM/nVMX: Use kvm_vcpu_map for accessing the shadow VMCS KarimAllah Ahmed
2019-01-23 18:10   ` Konrad Rzeszutek Wilk
2019-01-09  9:42 ` [PATCH v5 12/13] KVM/nVMX: Use kvm_vcpu_map for accessing the enlightened VMCS KarimAllah Ahmed
2019-01-23 18:11   ` Konrad Rzeszutek Wilk
2019-01-09  9:42 ` [PATCH v5 13/13] KVM/nVMX: Use page_address_valid in a few more locations KarimAllah Ahmed
2019-01-23 18:18   ` Konrad Rzeszutek Wilk
2019-01-25 18:17     ` Raslan, KarimAllah
2019-01-23 18:16 ` [PATCH v5 00/13] KVM/X86: Introduce a new guest mapping interface Konrad Rzeszutek Wilk
2019-01-25 18:28   ` Raslan, KarimAllah
2019-01-30 17:14     ` Paolo Bonzini
2019-01-31 13:03       ` Raslan, KarimAllah
2019-01-31 13:10         ` Paolo Bonzini

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