On Sat, 26 Nov 2022 06:33:15 +0000, "chenxiang (M)" <chenxiang66@xxxxxxxxxxxxx> wrote: > > > 在 2022/11/23 20:08, Marc Zyngier 写道: > > On Wed, 23 Nov 2022 01:42:36 +0000, > > chenxiang <chenxiang66@xxxxxxxxxxxxx> wrote: > >> From: Xiang Chen <chenxiang66@xxxxxxxxxxxxx> > >> > >> Currently the number of MSI vectors comes from register PCI_MSI_FLAGS > >> which should be power-of-2 in qemu, in some scenaries it is not the same as > >> the number that driver requires in guest, for example, a PCI driver wants > >> to allocate 6 MSI vecotrs in guest, but as the limitation, it will allocate > >> 8 MSI vectors. So it requires 8 MSI vectors in qemu while the driver in > >> guest only wants to allocate 6 MSI vectors. > >> > >> When GICv4.1 is enabled, it iterates over all possible MSIs and enable the > >> forwarding while the guest has only created some of mappings in the virtual > >> ITS, so some calls fail. The exception print is as following: > >> vfio-pci 0000:3a:00.1: irq bypass producer (token 000000008f08224d) registration > >> fails:66311 > >> > >> To avoid the issue, verify each MSI vector, skip some operations such as > >> request_irq() and irq_bypass_register_producer() for those invalid MSI vectors. > >> > >> Signed-off-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx> > >> --- > >> I reported the issue at the link: > >> https://lkml.kernel.org/lkml/87cze9lcut.wl-maz@xxxxxxxxxx/T/ > >> > >> Change Log: > >> v1 -> v2: > >> Verify each MSI vector in kernel instead of adding systemcall according to > >> Mar's suggestion > >> --- > >> arch/arm64/kvm/vgic/vgic-irqfd.c | 13 +++++++++++++ > >> arch/arm64/kvm/vgic/vgic-its.c | 36 ++++++++++++++++++++++++++++++++++++ > >> arch/arm64/kvm/vgic/vgic.h | 1 + > >> drivers/vfio/pci/vfio_pci_intrs.c | 33 +++++++++++++++++++++++++++++++++ > >> include/linux/kvm_host.h | 2 ++ > >> 5 files changed, 85 insertions(+) > >> > >> diff --git a/arch/arm64/kvm/vgic/vgic-irqfd.c b/arch/arm64/kvm/vgic/vgic-irqfd.c > >> index 475059b..71f6af57 100644 > >> --- a/arch/arm64/kvm/vgic/vgic-irqfd.c > >> +++ b/arch/arm64/kvm/vgic/vgic-irqfd.c > >> @@ -98,6 +98,19 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e, > >> return vgic_its_inject_msi(kvm, &msi); > >> } > >> +int kvm_verify_msi(struct kvm *kvm, > >> + struct kvm_kernel_irq_routing_entry *irq_entry) > >> +{ > >> + struct kvm_msi msi; > >> + > >> + if (!vgic_has_its(kvm)) > >> + return -ENODEV; > >> + > >> + kvm_populate_msi(irq_entry, &msi); > >> + > >> + return vgic_its_verify_msi(kvm, &msi); > >> +} > >> + > >> /** > >> * kvm_arch_set_irq_inatomic: fast-path for irqfd injection > >> */ > >> diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c > >> index 94a666d..8312a4a 100644 > >> --- a/arch/arm64/kvm/vgic/vgic-its.c > >> +++ b/arch/arm64/kvm/vgic/vgic-its.c > >> @@ -767,6 +767,42 @@ int vgic_its_inject_cached_translation(struct kvm *kvm, struct kvm_msi *msi) > >> return 0; > >> } > >> +int vgic_its_verify_msi(struct kvm *kvm, struct kvm_msi *msi) > >> +{ > >> + struct vgic_its *its; > >> + struct its_ite *ite; > >> + struct kvm_vcpu *vcpu; > >> + int ret = 0; > >> + > >> + if (!irqchip_in_kernel(kvm) || (msi->flags & ~KVM_MSI_VALID_DEVID)) > >> + return -EINVAL; > >> + > >> + if (!vgic_has_its(kvm)) > >> + return -ENODEV; > >> + > >> + its = vgic_msi_to_its(kvm, msi); > >> + if (IS_ERR(its)) > >> + return PTR_ERR(its); > >> + > >> + mutex_lock(&its->its_lock); > >> + if (!its->enabled) { > >> + ret = -EBUSY; > >> + goto unlock; > >> + } > >> + ite = find_ite(its, msi->devid, msi->data); > >> + if (!ite || !its_is_collection_mapped(ite->collection)) { > >> + ret = E_ITS_INT_UNMAPPED_INTERRUPT; > >> + goto unlock; > >> + } > >> + > >> + vcpu = kvm_get_vcpu(kvm, ite->collection->target_addr); > >> + if (!vcpu) > >> + ret = E_ITS_INT_UNMAPPED_INTERRUPT; > > I'm sorry, but what does this mean to the caller? This should never > > leak outside of the ITS code. > > Actually it is already leak outside of ITS code, and please see the > exception printk (E_ITS_INT_UNMAPPED_INTERRUPT is 0x10307 which is > equal to 66311): > > vfio-pci 0000:3a:00.1: irq bypass producer (token 000000008f08224d) registration fails:66311 > But that's hardly interpreted, which is the whole point. Only zero is considered a success value. > > Honestly, the whole things seems really complicated to avoid something > > that is only a harmless warning . > > It seems also waste some interrupts. Allocating and requesting some > interrupts but not used. What makes you think they are not used? A guest can install a mapping for those at any point. They won't be directly injected, but they will be delivered to the guest via the normal SW injection mechanism. M. -- Without deviation from the norm, progress is not possible.
