| Message ID | 20191024120938.11237-3-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: Don't mark hotplugged pages PG_reserved (including ZONE_DEVICE) | expand |
On Thu, Oct 24, 2019 at 5:10 AM David Hildenbrand <david@redhat.com> wrote: > > Right now, ZONE_DEVICE memory is always set PG_reserved. We want to > change that. > > KVM has this weird use case that you can map anything from /dev/mem > into the guest. pfn_valid() is not a reliable check whether the memmap > was initialized and can be touched. pfn_to_online_page() makes sure > that we have an initialized memmap (and don't have ZONE_DEVICE memory). > > Rewrite kvm_is_mmio_pfn() to make sure the function produces the > same result once we stop setting ZONE_DEVICE pages PG_reserved. > > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: "Radim Krčmář" <rkrcmar@redhat.com> > Cc: Sean Christopherson <sean.j.christopherson@intel.com> > Cc: Vitaly Kuznetsov <vkuznets@redhat.com> > Cc: Wanpeng Li <wanpengli@tencent.com> > Cc: Jim Mattson <jmattson@google.com> > Cc: Joerg Roedel <joro@8bytes.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Borislav Petkov <bp@alien8.de> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: KarimAllah Ahmed <karahmed@amazon.de> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > arch/x86/kvm/mmu.c | 29 +++++++++++++++++------------ > 1 file changed, 17 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 24c23c66b226..f03089a336de 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -2962,20 +2962,25 @@ static bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, > > static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) > { > + struct page *page = pfn_to_online_page(pfn); > + > + /* > + * ZONE_DEVICE pages are never online. Online pages that are reserved > + * either indicate the zero page or MMIO pages. > + */ > + if (page) > + return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)); > + > + /* > + * Anything with a valid (but not online) memmap could be ZONE_DEVICE. > + * Treat only UC/UC-/WC pages as MMIO. You might clarify that ZONE_DEVICE pages that belong to WB cacheable pmem have the correct memtype established by devm_memremap_pages(). Other than that, feel free to add: Reviewed-by: Dan Williams <dan.j.williams@intel.com>
On 05.11.19 02:37, Dan Williams wrote: > On Thu, Oct 24, 2019 at 5:10 AM David Hildenbrand <david@redhat.com> wrote: >> >> Right now, ZONE_DEVICE memory is always set PG_reserved. We want to >> change that. >> >> KVM has this weird use case that you can map anything from /dev/mem >> into the guest. pfn_valid() is not a reliable check whether the memmap >> was initialized and can be touched. pfn_to_online_page() makes sure >> that we have an initialized memmap (and don't have ZONE_DEVICE memory). >> >> Rewrite kvm_is_mmio_pfn() to make sure the function produces the >> same result once we stop setting ZONE_DEVICE pages PG_reserved. >> >> Cc: Paolo Bonzini <pbonzini@redhat.com> >> Cc: "Radim Krčmář" <rkrcmar@redhat.com> >> Cc: Sean Christopherson <sean.j.christopherson@intel.com> >> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> >> Cc: Wanpeng Li <wanpengli@tencent.com> >> Cc: Jim Mattson <jmattson@google.com> >> Cc: Joerg Roedel <joro@8bytes.org> >> Cc: Thomas Gleixner <tglx@linutronix.de> >> Cc: Ingo Molnar <mingo@redhat.com> >> Cc: Borislav Petkov <bp@alien8.de> >> Cc: "H. Peter Anvin" <hpa@zytor.com> >> Cc: KarimAllah Ahmed <karahmed@amazon.de> >> Cc: Michal Hocko <mhocko@kernel.org> >> Cc: Dan Williams <dan.j.williams@intel.com> >> Signed-off-by: David Hildenbrand <david@redhat.com> >> --- >> arch/x86/kvm/mmu.c | 29 +++++++++++++++++------------ >> 1 file changed, 17 insertions(+), 12 deletions(-) >> >> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c >> index 24c23c66b226..f03089a336de 100644 >> --- a/arch/x86/kvm/mmu.c >> +++ b/arch/x86/kvm/mmu.c >> @@ -2962,20 +2962,25 @@ static bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, >> >> static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) >> { >> + struct page *page = pfn_to_online_page(pfn); >> + >> + /* >> + * ZONE_DEVICE pages are never online. Online pages that are reserved >> + * either indicate the zero page or MMIO pages. >> + */ >> + if (page) >> + return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)); >> + >> + /* >> + * Anything with a valid (but not online) memmap could be ZONE_DEVICE. >> + * Treat only UC/UC-/WC pages as MMIO. > > You might clarify that ZONE_DEVICE pages that belong to WB cacheable > pmem have the correct memtype established by devm_memremap_pages(). /* * Anything with a valid (but not online) memmap could be ZONE_DEVICE. * Treat only UC/UC-/WC pages as MMIO. devm_memremap_pages() established * the correct memtype for WB cacheable ZONE_DEVICE pages. */ Thanks! > > Other than that, feel free to add: > > Reviewed-by: Dan Williams <dan.j.williams@intel.com> >
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 24c23c66b226..f03089a336de 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2962,20 +2962,25 @@ static bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) { + struct page *page = pfn_to_online_page(pfn); + + /* + * ZONE_DEVICE pages are never online. Online pages that are reserved + * either indicate the zero page or MMIO pages. + */ + if (page) + return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)); + + /* + * Anything with a valid (but not online) memmap could be ZONE_DEVICE. + * Treat only UC/UC-/WC pages as MMIO. + */ if (pfn_valid(pfn)) - return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)) && - /* - * Some reserved pages, such as those from NVDIMM - * DAX devices, are not for MMIO, and can be mapped - * with cached memory type for better performance. - * However, the above check misconceives those pages - * as MMIO, and results in KVM mapping them with UC - * memory type, which would hurt the performance. - * Therefore, we check the host memory type in addition - * and only treat UC/UC-/WC pages as MMIO. - */ - (!pat_enabled() || pat_pfn_immune_to_uc_mtrr(pfn)); + return !pat_enabled() || pat_pfn_immune_to_uc_mtrr(pfn); + /* + * Any RAM that has no memmap (e.g., mapped via /dev/mem) is not MMIO. + */ return !e820__mapped_raw_any(pfn_to_hpa(pfn), pfn_to_hpa(pfn + 1) - 1, E820_TYPE_RAM);
Right now, ZONE_DEVICE memory is always set PG_reserved. We want to change that. KVM has this weird use case that you can map anything from /dev/mem into the guest. pfn_valid() is not a reliable check whether the memmap was initialized and can be touched. pfn_to_online_page() makes sure that we have an initialized memmap (and don't have ZONE_DEVICE memory). Rewrite kvm_is_mmio_pfn() to make sure the function produces the same result once we stop setting ZONE_DEVICE pages PG_reserved. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "Radim Krčmář" <rkrcmar@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Wanpeng Li <wanpengli@tencent.com> Cc: Jim Mattson <jmattson@google.com> Cc: Joerg Roedel <joro@8bytes.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: KarimAllah Ahmed <karahmed@amazon.de> Cc: Michal Hocko <mhocko@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- arch/x86/kvm/mmu.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-)