Once we enable ARCH_SUPPORTS_MEMORY_FAILURE on arm64, notifications for broken memory can call memory_failure() in mm/memory-failure.c to offline pages of memory, possibly signalling user space processes and notifying all the in-kernel users. memory_failure() has two modes, early and late. Early is used by machine-managers like Qemu to receive a notification when a memory error is notified to the host. These can then be relayed to the guest before the affected page is accessed. To enable this, the process must set PR_MCE_KILL_EARLY in PR_MCE_KILL_SET using the prctl() syscall. Once the early notification has been handled, nothing stops the machine-manager or guest from accessing the affected page. If the machine-manager does this the page will fail to be mapped and SIGBUS will be sent. This patch adds the equivalent path for when the guest accesses the page, sending SIGBUS to the machine-manager. These two signals can be distinguished by the machine-manager using their si_code: BUS_MCEERR_AO for 'action optional' early notifications, and BUS_MCEERR_AR for 'action required' synchronous/late notifications. Do as x86 does, and deliver the SIGBUS when we discover pfn == KVM_PFN_ERR_HWPOISON. Use the hugepage size as si_addr_lsb if this vma was allocated as a hugepage. Transparent hugepages will be split by memory_failure() before we see them here. Cc: Punit Agrawal <punit.agrawal@xxxxxxx> Signed-off-by: James Morse <james.morse@xxxxxxx> --- arm64 has ARCH_SUPPORTS_MEMORY_FAILURE in linux-next, so can enable MEMORY_FAILURE. This patch will build without those changes as KVM_PFN_ERR_HWPOISON is always defined. Changes since v2: * Just the commit message. 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 ... [0] https://www.spinics.net/lists/arm-kernel/msg581657.html 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
