* [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not
@ 2016-06-22 2:34 KarimAllah Ahmed
2016-06-22 13:41 ` Paolo Bonzini
0 siblings, 1 reply; 7+ messages in thread
From: KarimAllah Ahmed @ 2016-06-22 2:34 UTC (permalink / raw)
To: linux-kernel, kvm, x86
Cc: KarimAllah Ahmed, Thomas Gleixner, Ingo Molnar, H . Peter Anvin,
Paolo Bonzini, Radim Krčmář,
Borislav Petkov, Denys Vlasenko, Andrew Morton, Toshi Kani,
Tony Luck
pfn_valid check is not sufficient because it only checks if a page has a struct
page or not, if for example "mem=" was passed to the kernel some valid pages
won't have a struct page. This means that if guests were assigned valid memory
that lies after the mem= boundary it will be passed uncached to the guest no
matter what the guest caching attributes are for this memory.
Use the original e820 map to check whether a certain pfn belongs to RAM or not.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-kernel@vger.kernel.org
Cc: kvm@vger.kernel.org
Cc: x86@kernel.org
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
---
arch/x86/include/asm/e820.h | 1 +
arch/x86/kernel/e820.c | 18 ++++++++++++++++++
arch/x86/kvm/mmu.c | 2 +-
3 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/e820.h b/arch/x86/include/asm/e820.h
index 3ab0537..2d4f7d8 100644
--- a/arch/x86/include/asm/e820.h
+++ b/arch/x86/include/asm/e820.h
@@ -16,6 +16,7 @@ extern struct e820map e820_saved;
extern unsigned long pci_mem_start;
extern int e820_any_mapped(u64 start, u64 end, unsigned type);
extern int e820_all_mapped(u64 start, u64 end, unsigned type);
+extern bool e820_is_ram(u64 addr);
extern void e820_add_region(u64 start, u64 size, int type);
extern void e820_print_map(char *who);
extern int
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 621b501..387cdba 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -105,6 +105,24 @@ int __init e820_all_mapped(u64 start, u64 end, unsigned type)
return 0;
}
+bool
+e820_is_ram(u64 addr)
+{
+ int i;
+
+ for (i = 0; i < e820_saved.nr_map; i++) {
+ struct e820entry *ei = &e820_saved.map[i];
+
+ if (ei->type != E820_RAM)
+ continue;
+ if ((addr >= ei->addr) && (addr < (ei->addr + ei->size)))
+ return true;
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(e820_is_ram);
+
/*
* Add a memory region to the kernel e820 map.
*/
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 24e8001..5e07bf5 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2507,7 +2507,7 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
if (pfn_valid(pfn))
return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn));
- return true;
+ return !e820_is_ram(pfn << PAGE_SHIFT);
}
static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
--
2.8.2
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not
2016-06-22 2:34 [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not KarimAllah Ahmed
@ 2016-06-22 13:41 ` Paolo Bonzini
2016-06-22 14:11 ` Raslan, KarimAllah
2016-09-15 5:54 ` Raslan, KarimAllah
0 siblings, 2 replies; 7+ messages in thread
From: Paolo Bonzini @ 2016-06-22 13:41 UTC (permalink / raw)
To: KarimAllah Ahmed, linux-kernel, kvm, x86
Cc: Thomas Gleixner, Ingo Molnar, H . Peter Anvin,
Radim Krčmář,
Borislav Petkov, Denys Vlasenko, Andrew Morton, Toshi Kani,
Tony Luck
On 22/06/2016 04:34, KarimAllah Ahmed wrote:
> pfn_valid check is not sufficient because it only checks if a page has a struct
> page or not, if for example "mem=" was passed to the kernel some valid pages
> won't have a struct page. This means that if guests were assigned valid memory
> that lies after the mem= boundary it will be passed uncached to the guest no
> matter what the guest caching attributes are for this memory.
How can you pass memory after the mem= boundary to the guest?
Paolo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not
2016-06-22 13:41 ` Paolo Bonzini
@ 2016-06-22 14:11 ` Raslan, KarimAllah
2016-09-15 5:54 ` Raslan, KarimAllah
1 sibling, 0 replies; 7+ messages in thread
From: Raslan, KarimAllah @ 2016-06-22 14:11 UTC (permalink / raw)
To: Paolo Bonzini, linux-kernel, kvm, x86
Cc: Thomas Gleixner, Ingo Molnar, H . Peter Anvin,
Radim Krčmář,
Borislav Petkov, Denys Vlasenko, Andrew Morton, Toshi Kani,
Tony Luck
On 6/22/16, 3:41 PM, "Paolo Bonzini" <pbonzini@redhat.com> wrote:
>
>
>On 22/06/2016 04:34, KarimAllah Ahmed wrote:
>> pfn_valid check is not sufficient because it only checks if a page has a struct
>> page or not, if for example "mem=" was passed to the kernel some valid pages
>> won't have a struct page. This means that if guests were assigned valid memory
>> that lies after the mem= boundary it will be passed uncached to the guest no
>> matter what the guest caching attributes are for this memory.
>
>How can you pass memory after the mem= boundary to the guest?
Memory regions can be assigned to the guest as long as you've a valid host
virtual address. You can always get a host virtual address for any RAM that
lives after 'mem=' for example by simply mmaping /dev/mem or even using some
special kernel module to mmap these regions from user space.
>
>Paolo
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not
2016-06-22 13:41 ` Paolo Bonzini
2016-06-22 14:11 ` Raslan, KarimAllah
@ 2016-09-15 5:54 ` Raslan, KarimAllah
2016-09-15 6:22 ` Paolo Bonzini
1 sibling, 1 reply; 7+ messages in thread
From: Raslan, KarimAllah @ 2016-09-15 5:54 UTC (permalink / raw)
To: Paolo Bonzini
Cc: linux-kernel, kvm, x86, Thomas Gleixner, Ingo Molnar,
H . Peter Anvin, Radim Krčmář,
Borislav Petkov, Denys Vlasenko, Andrew Morton, Toshi Kani,
Tony Luck
> On Jun 22, 2016, at 3:41 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
>
>
> On 22/06/2016 04:34, KarimAllah Ahmed wrote:
>> pfn_valid check is not sufficient because it only checks if a page has a struct
>> page or not, if for example "mem=" was passed to the kernel some valid pages
>> won't have a struct page. This means that if guests were assigned valid memory
>> that lies after the mem= boundary it will be passed uncached to the guest no
>> matter what the guest caching attributes are for this memory.
>
> How can you pass memory after the mem= boundary to the guest?
Does my previous reply answer your question?
>
> Paolo
>
Amazon Development Center Germany GmbH
Berlin - Dresden - Aachen
main office: Krausenstr. 38, 10117 Berlin
Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger
Ust-ID: DE289237879
Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not
2016-09-15 5:54 ` Raslan, KarimAllah
@ 2016-09-15 6:22 ` Paolo Bonzini
2016-09-15 16:04 ` Kani, Toshimitsu
0 siblings, 1 reply; 7+ messages in thread
From: Paolo Bonzini @ 2016-09-15 6:22 UTC (permalink / raw)
To: Raslan, KarimAllah
Cc: linux-kernel, kvm, x86, Thomas Gleixner, Ingo Molnar,
H . Peter Anvin, Radim Krčmář,
Borislav Petkov, Denys Vlasenko, Andrew Morton, Toshi Kani,
Tony Luck
On 15/09/2016 07:54, Raslan, KarimAllah wrote:
>
>> On Jun 22, 2016, at 3:41 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>
>>
>>
>> On 22/06/2016 04:34, KarimAllah Ahmed wrote:
>>> pfn_valid check is not sufficient because it only checks if a page has a struct
>>> page or not, if for example "mem=" was passed to the kernel some valid pages
>>> won't have a struct page. This means that if guests were assigned valid memory
>>> that lies after the mem= boundary it will be passed uncached to the guest no
>>> matter what the guest caching attributes are for this memory.
>>
>> How can you pass memory after the mem= boundary to the guest?
>
> Does my previous reply answer your question?
Yes, but I'm not sure it's the right way to do it. Looking at the e820
memory map seems pretty hacky.
Paolo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not
2016-09-15 6:22 ` Paolo Bonzini
@ 2016-09-15 16:04 ` Kani, Toshimitsu
2016-09-15 16:22 ` Paolo Bonzini
0 siblings, 1 reply; 7+ messages in thread
From: Kani, Toshimitsu @ 2016-09-15 16:04 UTC (permalink / raw)
To: pbonzini, karahmed
Cc: kvm, linux-kernel, bp, tglx, x86, akpm, hpa, mingo, tony.luck,
dvlasenk, rkrcmar
On Thu, 2016-09-15 at 08:22 +0200, Paolo Bonzini wrote:
>
> On 15/09/2016 07:54, Raslan, KarimAllah wrote:
> >
> >
> > >
> > > On Jun 22, 2016, at 3:41 PM, Paolo Bonzini <pbonzini@redhat.com>
> > > wrote:
> > >
> > >
> > >
> > > On 22/06/2016 04:34, KarimAllah Ahmed wrote:
> > > >
> > > > pfn_valid check is not sufficient because it only checks if a
> > > > page has a struct page or not, if for example "mem=" was passed
> > > > to the kernel some valid pages won't have a struct page. This
> > > > means that if guests were assigned valid memory that lies after
> > > > the mem= boundary it will be passed uncached to the guest no
> > > > matter what the guest caching attributes are for this memory.
> > >
> > > How can you pass memory after the mem= boundary to the guest?
> >
> > Does my previous reply answer your question?
>
> Yes, but I'm not sure it's the right way to do it. Looking at the
> e820 memory map seems pretty hacky.
Can you use region_intersects() for this check? See memremap() as an
example using this interface.
-Toshi
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not
2016-09-15 16:04 ` Kani, Toshimitsu
@ 2016-09-15 16:22 ` Paolo Bonzini
0 siblings, 0 replies; 7+ messages in thread
From: Paolo Bonzini @ 2016-09-15 16:22 UTC (permalink / raw)
To: Kani, Toshimitsu, karahmed
Cc: kvm, linux-kernel, bp, tglx, x86, akpm, hpa, mingo, tony.luck,
dvlasenk, rkrcmar
On 15/09/2016 18:04, Kani, Toshimitsu wrote:
> On Thu, 2016-09-15 at 08:22 +0200, Paolo Bonzini wrote:
>>
>> On 15/09/2016 07:54, Raslan, KarimAllah wrote:
>>>
>>>
>>>>
>>>> On Jun 22, 2016, at 3:41 PM, Paolo Bonzini <pbonzini@redhat.com>
>>>> wrote:
>>>>
>>>>
>>>>
>>>> On 22/06/2016 04:34, KarimAllah Ahmed wrote:
>>>>>
>>>>> pfn_valid check is not sufficient because it only checks if a
>>>>> page has a struct page or not, if for example "mem=" was passed
>>>>> to the kernel some valid pages won't have a struct page. This
>>>>> means that if guests were assigned valid memory that lies after
>>>>> the mem= boundary it will be passed uncached to the guest no
>>>>> matter what the guest caching attributes are for this memory.
>>>>
>>>> How can you pass memory after the mem= boundary to the guest?
>>>
>>> Does my previous reply answer your question?
>>
>> Yes, but I'm not sure it's the right way to do it. Looking at the
>> e820 memory map seems pretty hacky.
>
> Can you use region_intersects() for this check? See memremap() as an
> example using this interface.
This one seems more generic but very slow.
Paolo
^ permalink raw reply [flat|nested] 7+ messages in thread
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2016-06-22 2:34 [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not KarimAllah Ahmed
2016-06-22 13:41 ` Paolo Bonzini
2016-06-22 14:11 ` Raslan, KarimAllah
2016-09-15 5:54 ` Raslan, KarimAllah
2016-09-15 6:22 ` Paolo Bonzini
2016-09-15 16:04 ` Kani, Toshimitsu
2016-09-15 16:22 ` Paolo Bonzini
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