On Wed, May 24, 2017 at 05:32:50PM +0100, James Morse wrote: > Once we enable ARCH_SUPPORTS_MEMORY_FAILURE on arm64, notifications for > broken memory can call memory_failure() in mm/memory-failure.c to deliver > SIGBUS to any user space process using the page, and notify all the > in-kernel users. > > If the page corresponded with guest memory, KVM will unmap this page > from its stage2 page tables. The user space process that allocated > this memory may have never touched this page in which case it may not > be mapped meaning SIGBUS won't be delivered. Sorry, I don't remember, what is the scenario where KVM can have a mapping in stage 2 without there being a corresponding mapping for user space? > > This works well until a guest accesses that page, and KVM discovers > pfn == KVM_PFN_ERR_HWPOISON when it comes to process the stage2 fault. > > Do as x86 does, and deliver the SIGBUS when we discover > KVM_PFN_ERR_HWPOISON. Use the stage2 mapping size as the si_addr_lsb But this part about the stage 2 mapping size is not what the code does. It uses the granularity of the mmap region, if I'm not mistaken. I lost track of what the right thing was, can you remind me? Thanks, -Christoffer > as this matches the user space mapping size. > > Cc: Punit Agrawal <punit.agrawal@xxxxxxx> > Signed-off-by: James Morse <james.morse@xxxxxxx> > > --- > This will be needed once we enable ARCH_SUPPORTS_MEMORY_FAILURE for > arm64[0]. It is harmless until then as KVM_PFN_ERR_HWPOISON will > never be seen. > > Changes since v1: > * Pass the vma to kvm_send_hwpoison_signal(), used Punit's huge_page_shift() > calculation to find the block size. > * ... tested against hugepage not transparent huge page ... > > Today we will inherit some existing breakage between KVM, hugepages > and hwpoison. Patch at [1]. > > > [0] https://www.spinics.net/lists/arm-kernel/msg581657.html > [1] https://marc.info/?l=linux-mm&m=149564219918427&w=2 > > virt/kvm/arm/mmu.c | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c > index 313ee646480f..eaa29aeb7c5b 100644 > --- a/virt/kvm/arm/mmu.c > +++ b/virt/kvm/arm/mmu.c > @@ -20,6 +20,7 @@ > #include <linux/kvm_host.h> > #include <linux/io.h> > #include <linux/hugetlb.h> > +#include <linux/sched/signal.h> > #include <trace/events/kvm.h> > #include <asm/pgalloc.h> > #include <asm/cacheflush.h> > @@ -1249,6 +1250,24 @@ static void coherent_cache_guest_page(struct kvm_vcpu *vcpu, kvm_pfn_t pfn, > __coherent_cache_guest_page(vcpu, pfn, size); > } > > +static void kvm_send_hwpoison_signal(unsigned long address, > + struct vm_area_struct *vma) > +{ > + siginfo_t info; > + > + info.si_signo = SIGBUS; > + info.si_errno = 0; > + info.si_code = BUS_MCEERR_AR; > + info.si_addr = (void __user *)address; > + > + if (is_vm_hugetlb_page(vma)) > + info.si_addr_lsb = huge_page_shift(hstate_vma(vma)); > + else > + info.si_addr_lsb = PAGE_SHIFT; > + > + send_sig_info(SIGBUS, &info, current); > +} > + > static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > struct kvm_memory_slot *memslot, unsigned long hva, > unsigned long fault_status) > @@ -1318,6 +1337,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > smp_rmb(); > > pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writable); > + if (pfn == KVM_PFN_ERR_HWPOISON) { > + kvm_send_hwpoison_signal(hva, vma); > + return 0; > + } > if (is_error_noslot_pfn(pfn)) > return -EFAULT; > > -- > 2.11.0 > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
