Hi James, One comment at the end.
James Morse <[email protected]> writes: > Once we enable ARCH_SUPPORTS_MEMORY_FAILURE on arm64[0], 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. > > When this happens 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 > as this matches the user space mapping size. > > Signed-off-by: James Morse <[email protected]> > CC: gengdongjiu <[email protected]> > --- > Without this patch both kvmtool and Qemu exit as the KVM_RUN ioctl() returns > EFAULT. > QEMU: error: kvm run failed Bad address > LVKM: KVM_RUN failed: Bad address > > With this patch both kvmtool and Qemu receive SIGBUS ... and then exit. > In the future Qemu can use this signal to notify the guest, for more details > see hwpoison[1]. > > [0] https://www.spinics.net/lists/arm-kernel/msg560009.html > [1] > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/vm/hwpoison.txt > > > arch/arm/kvm/mmu.c | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c > index 962616fd4ddd..9d1aa294e88f 100644 > --- a/arch/arm/kvm/mmu.c > +++ b/arch/arm/kvm/mmu.c > @@ -20,8 +20,10 @@ > #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/siginfo.h> > #include <asm/cacheflush.h> > #include <asm/kvm_arm.h> > #include <asm/kvm_mmu.h> > @@ -1237,6 +1239,23 @@ 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, bool hugetlb) > +{ > + siginfo_t info; > + > + info.si_signo = SIGBUS; > + info.si_errno = 0; > + info.si_code = BUS_MCEERR_AR; > + info.si_addr = (void __user *)address; > + > + if (hugetlb) > + info.si_addr_lsb = PMD_SHIFT; > + 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) > @@ -1306,6 +1325,10 @@ 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, hugetlb); > + return 0; > + } > if (is_error_noslot_pfn(pfn)) > return -EFAULT; The changes look good to me. Though in essence as mentioned in the commit log we are not doing anything different to x86 here. Worth moving kvm_send_hwpoison_signal to an architecture agostic location and using it from there? In any case, FWIW, Reviewed-by: Punit Agrawal <[email protected]> Thanks. _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
