| Message ID | 1466562866-31524-1-git-send-email-karahmed@amazon.de (mailing list archive) |
|---|---|
| State | New, archived |
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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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 >
> 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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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,
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(-)