On Wed, Jul 22, 2009 at 05:41:22PM +0300, Michael S. Tsirkin wrote:
> Kernels up to 2.6.31 have a bug: MSI entries where looked at when irq
> is acked, address_lo was interpreted as irqchip, and
> address_hi as pin. If that matches a real interrupt this prevents
> ack notifier from being processed.
>
> Since these kernels ignore the value for address_hi when delivering
> MSI, work around this by setting a value that never matches an
> interrupt pin number.
>
> Pointers to relevant kernel code, for reference: in kernel v2.6.31-rc3:
> kvm_notify_acked_irq - fails to check irq type,
> kvm_set_msi - ignored address_hi in message
Ugh, its still broken AFAICS? If so, what is the plan to fix it?
Also, you'd never want to use address_hi for something, in the
future?
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> qemu-kvm.c | 32 ++++++++++++++++++++++++++++++--
> 1 files changed, 30 insertions(+), 2 deletions(-)
>
> diff --git a/qemu-kvm.c b/qemu-kvm.c
> index cebaa65..ec6d583 100644
> --- a/qemu-kvm.c
> +++ b/qemu-kvm.c
> @@ -38,6 +38,32 @@
> #error libkvm: userspace and kernel version mismatch
> #endif
>
> +#ifdef KVM_CAP_IRQ_ROUTING
> +/* Broken MSI routing work-around:
> + * Kernels up to 2.6.31 have a bug: MSI entries where looked at when irq
> + * is acked, address_lo was interpreted as irqchip, and
> + * address_hi as pin. If that matches a real interrupt this prevents
> + * ack notifier from being processed.
> + *
> + * Since these kernels ignore the value for address_hi when delivering
> + * MSI, work around this by setting a value that never matches an
> + * interrupt pin number.
> + */
> +#define KVM_BROKEN_MSI_ROUTING 1
> +static inline
> +void kvm_broken_msi_fix(struct kvm_irq_routing_entry *entry)
> +{
> + if (entry->type == KVM_IRQ_ROUTING_MSI) {
> + entry->u.msi.address_hi = 0xffffffff;
> + }
> +}
> +static inline
> +unsigned kvm_broken_msi_address_hi(struct kvm_irq_routing_entry *entry)
> +{
> + return 0xffffffff;
> +}
> +#endif
> +
> int kvm_allowed = 1;
> int kvm_irqchip = 1;
> int kvm_pit = 1;
> @@ -1433,6 +1459,7 @@ int kvm_add_routing_entry(kvm_context_t kvm,
> new->type = entry->type;
> new->flags = entry->flags;
> new->u = entry->u;
> + kvm_broken_msi_fix(new);
>
> set_gsi(kvm, entry->gsi);
>
> @@ -1489,7 +1516,7 @@ int kvm_del_routing_entry(kvm_context_t kvm,
> if (e->u.msi.address_lo ==
> entry->u.msi.address_lo
> && e->u.msi.address_hi ==
> - entry->u.msi.address_hi
> + kvm_broken_msi_address_hi(entry)
> && e->u.msi.data == entry->u.msi.data) {
> p = &kvm->irq_routes->
> entries[--kvm->irq_routes->nr];
> @@ -1550,9 +1577,10 @@ int kvm_update_routing_entry(kvm_context_t kvm,
> break;
> case KVM_IRQ_ROUTING_MSI:
> if (e->u.msi.address_lo == entry->u.msi.address_lo &&
> - e->u.msi.address_hi == entry->u.msi.address_hi &&
> + e->u.msi.address_hi == kvm_broken_msi_address_hi(entry) &&
> e->u.msi.data == entry->u.msi.data) {
> memcpy(&e->u.msi, &newentry->u.msi, sizeof e->u.msi);
> + kvm_broken_msi_fix(e);
> return 0;
> }
> break;
> --
> 1.6.2.5
> --
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