KVM: PPC: Book3S HV: XIVE: fix page offset when clearing ESB pages

Under XIVE, the ESB pages of an interrupt are used for interrupt
management (EOI) and triggering. They are made available to guests
through a mapping of the XIVE KVM device.

When a device is passed-through, the passthru_irq helpers,
kvmppc_xive_set_mapped() and kvmppc_xive_clr_mapped(), clear the ESB
pages of the guest IRQ number being mapped and let the VM fault
handler repopulate with the correct page.

The ESB pages are mapped at offset 4 (KVM_XIVE_ESB_PAGE_OFFSET) in the
KVM device mapping. Unfortunately, this offset was not taken into
account when clearing the pages. This lead to issues with the
passthrough devices for which the interrupts were not functional under
some guest configuration (tg3 and single CPU) or in any configuration
(e1000e adapter).

Signed-off-by: Cédric Le Goater <clg@kaod.org>
---

 if unmap_mapping_pages() could be called from a module, we would
 simplify a bit this code.

 arch/powerpc/kvm/book3s_xive_native.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

On Tue, 28 May 2019 23:13:24 +0200
Cédric Le Goater <clg@kaod.org> wrote:

> Under XIVE, the ESB pages of an interrupt are used for interrupt
> management (EOI) and triggering. They are made available to guests
> through a mapping of the XIVE KVM device.
> 
> When a device is passed-through, the passthru_irq helpers,
> kvmppc_xive_set_mapped() and kvmppc_xive_clr_mapped(), clear the ESB
> pages of the guest IRQ number being mapped and let the VM fault
> handler repopulate with the correct page.
> 
> The ESB pages are mapped at offset 4 (KVM_XIVE_ESB_PAGE_OFFSET) in the
> KVM device mapping. Unfortunately, this offset was not taken into
> account when clearing the pages. This lead to issues with the

Good catch ! :)

Reviwed-by: Greg Kurz <groug@kaod.org>

> passthrough devices for which the interrupts were not functional under
> some guest configuration (tg3 and single CPU) or in any configuration

And this patch fixes my tg3 use case.

Tested-by: Greg Kurz <groug@kaod.org>

> (e1000e adapter).
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
> 
>  if unmap_mapping_pages() could be called from a module, we would
>  simplify a bit this code.
> 
>  arch/powerpc/kvm/book3s_xive_native.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> index 8b762e3ebbc5..5596c8ec221a 100644
> --- a/arch/powerpc/kvm/book3s_xive_native.c
> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> @@ -172,6 +172,7 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev,
>  static int kvmppc_xive_native_reset_mapped(struct kvm *kvm, unsigned long irq)
>  {
>  	struct kvmppc_xive *xive = kvm->arch.xive;
> +	pgoff_t esb_pgoff = KVM_XIVE_ESB_PAGE_OFFSET + irq * 2;
>  
>  	if (irq >= KVMPPC_XIVE_NR_IRQS)
>  		return -EINVAL;
> @@ -185,7 +186,7 @@ static int kvmppc_xive_native_reset_mapped(struct kvm *kvm, unsigned long irq)
>  	mutex_lock(&xive->mapping_lock);
>  	if (xive->mapping)
>  		unmap_mapping_range(xive->mapping,
> -				    irq * (2ull << PAGE_SHIFT),
> +				    esb_pgoff << PAGE_SHIFT,
>  				    2ull << PAGE_SHIFT, 1);
>  	mutex_unlock(&xive->mapping_lock);
>  	return 0;

On Tue, May 28, 2019 at 11:13:24PM +0200, Cédric Le Goater wrote:
> Under XIVE, the ESB pages of an interrupt are used for interrupt
> management (EOI) and triggering. They are made available to guests
> through a mapping of the XIVE KVM device.
> 
> When a device is passed-through, the passthru_irq helpers,
> kvmppc_xive_set_mapped() and kvmppc_xive_clr_mapped(), clear the ESB
> pages of the guest IRQ number being mapped and let the VM fault
> handler repopulate with the correct page.
> 
> The ESB pages are mapped at offset 4 (KVM_XIVE_ESB_PAGE_OFFSET) in the
> KVM device mapping. Unfortunately, this offset was not taken into
> account when clearing the pages. This lead to issues with the
> passthrough devices for which the interrupts were not functional under
> some guest configuration (tg3 and single CPU) or in any configuration
> (e1000e adapter).
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>

Thanks, patch applied to my kvm-ppc-fixes branch.

Paul.