On Thu, 31 Jul 2025, dm...@proton.me wrote:
> From: Denis Mukhin <dmuk...@ford.com>
>
> Enable virtual NS16550 for PVH domains in xl.
>
> {map,unmap}_domain_emuirq_pirq() infrastructure is modified by adding new
> type of interrupt resources 'IRQ_EMU' which means 'emulated device IRQ'
> (similarly to IRQ_MSI_EMU).
>
> This is necessary to for IOAPIC emulation code to skip IRQ->PIRQ mapping
> (vioapic_hwdom_map_gsi()) when guest OS unmasks vIOAPIC pin corresponding to
> virtual device's IRQ.
>
> Also, hvm_gsi_eoi() is modified to trigger assertion in hvm_gsi_deassert()
> path for ISA IRQs.
>
> Signed-off-by: Denis Mukhin <dmuk...@ford.com>
> ---
> Changes since v3:
> - new patch
> ---
> tools/libs/light/libxl_x86.c | 2 +-
> xen/arch/x86/domain.c | 2 ++
> xen/arch/x86/hvm/vioapic.c | 10 ++++++++++
> xen/arch/x86/include/asm/irq.h | 1 +
> xen/common/emul/vuart/vuart-ns16550.c | 27 +++++++++++++++++++++++++--
> xen/drivers/passthrough/x86/hvm.c | 9 ++++-----
> 6 files changed, 43 insertions(+), 8 deletions(-)
>
> diff --git a/tools/libs/light/libxl_x86.c b/tools/libs/light/libxl_x86.c
> index 0f039ca65a88..a40647c06cb9 100644
> --- a/tools/libs/light/libxl_x86.c
> +++ b/tools/libs/light/libxl_x86.c
> @@ -54,7 +54,7 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
> break;
> case LIBXL_DOMAIN_TYPE_PVH:
> config->arch.emulation_flags = XEN_X86_EMU_LAPIC;
> - libxl__arch_domain_vuart_unsupported(gc, d_config, config);
> + libxl__arch_domain_vuart_enable(gc, d_config, config);
> break;
> case LIBXL_DOMAIN_TYPE_PV:
> config->arch.emulation_flags = 0;
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index 6a010a509a60..39b0c0b199b9 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -769,12 +769,14 @@ static bool emulation_flags_ok(const struct domain *d,
> uint32_t emflags)
> {
> .caps = CAP_HVM | CAP_HWDOM,
> .min = X86_EMU_LAPIC | X86_EMU_IOAPIC | X86_EMU_VPCI,
> + .opt = X86_EMU_NS16550,
> },
>
> /* PVH domU */
> {
> .caps = CAP_HVM | CAP_DOMU,
> .min = X86_EMU_LAPIC,
> + .opt = X86_EMU_NS16550,
> },
>
> /* HVM domU */
> diff --git a/xen/arch/x86/hvm/vioapic.c b/xen/arch/x86/hvm/vioapic.c
> index 7c725f9e471f..86fe3aa4a201 100644
> --- a/xen/arch/x86/hvm/vioapic.c
> +++ b/xen/arch/x86/hvm/vioapic.c
> @@ -177,6 +177,16 @@ static int vioapic_hwdom_map_gsi(unsigned int gsi,
> unsigned int trig,
>
> ASSERT(is_hardware_domain(currd));
>
> + /*
> + * Interrupt is claimed by one of the platform virtual devices (e.g.
> + * NS16550); do nothing.
> + */
> + read_lock(&currd->event_lock);
> + ret = domain_pirq_to_emuirq(currd, gsi);
> + read_unlock(&currd->event_lock);
> + if ( ret != IRQ_UNBOUND )
> + return 0;
> +
> /* Interrupt has been unmasked, bind it now. */
> ret = mp_register_gsi(gsi, trig, pol);
> if ( ret == -EEXIST )
> diff --git a/xen/arch/x86/include/asm/irq.h b/xen/arch/x86/include/asm/irq.h
> index 8c81f66434a8..731d2bbbb1b4 100644
> --- a/xen/arch/x86/include/asm/irq.h
> +++ b/xen/arch/x86/include/asm/irq.h
> @@ -221,6 +221,7 @@ void cleanup_domain_irq_mapping(struct domain *d);
> #define IRQ_UNBOUND (-1)
> #define IRQ_PT (-2)
> #define IRQ_MSI_EMU (-3)
> +#define IRQ_EMU (-4)
>
> bool cpu_has_pending_apic_eoi(void);
>
> diff --git a/xen/common/emul/vuart/vuart-ns16550.c
> b/xen/common/emul/vuart/vuart-ns16550.c
> index 48bbf58264fe..9ec9aed2c594 100644
> --- a/xen/common/emul/vuart/vuart-ns16550.c
> +++ b/xen/common/emul/vuart/vuart-ns16550.c
> @@ -355,7 +355,9 @@ static void ns16550_irq_assert(const struct vuart_ns16550
> *vdev)
> struct domain *d = vdev->owner;
> int vector;
>
> - if ( has_vpic(d) ) /* HVM */
> + if ( has_vioapic(d) && !has_vpic(d) ) /* PVH */
> + vector = hvm_ioapic_assert(d, vdev->irq, false);
> + else if ( has_vpic(d) ) /* HVM */
> vector = hvm_isa_irq_assert(d, vdev->irq, vioapic_get_vector);
> else
> ASSERT_UNREACHABLE();
> @@ -367,7 +369,9 @@ static void ns16550_irq_deassert(const struct
> vuart_ns16550 *vdev)
> {
> struct domain *d = vdev->owner;
>
> - if ( has_vpic(d) ) /* HVM */
> + if ( has_vioapic(d) && !has_vpic(d) ) /* PVH */
> + hvm_ioapic_deassert(d, vdev->irq);
> + else if ( has_vpic(d) ) /* HVM */
> hvm_isa_irq_deassert(d, vdev->irq);
> else
> ASSERT_UNREACHABLE();
> @@ -889,6 +893,17 @@ static int cf_check ns16550_init(struct domain *d,
> return rc;
> }
>
> + /* Claim virtual IRQ */
> + write_lock(&d->event_lock);
> + rc = map_domain_emuirq_pirq(d, r->addr, IRQ_EMU);
> + write_unlock(&d->event_lock);
> + if ( rc )
> + {
> + pr_err("%s: virtual IRQ#%"PRIu64": cannot claim: %d\n",
> + desc->name, r->addr, rc);
> + return rc;
> + }
> +
> vdev->irq = r->addr;
> }
> else
> @@ -919,12 +934,20 @@ static int cf_check ns16550_init(struct domain *d,
> static void cf_check ns16550_deinit(struct domain *d)
> {
> struct vuart_ns16550 *vdev = d->arch.hvm.vuart;
> + int rc;
>
> if ( !vdev )
> return;
>
> spin_lock(&vdev->lock);
>
> + rc = unmap_domain_pirq_emuirq(vdev->owner, vdev->irq);
> + if ( rc )
> + {
> + pr_err("%s: virtual IRQ#%d: cannot unclaim: %d\n",
> + vdev->name, vdev->irq, rc);
> + }
write_lock(&d->event_lock); ?
> ns16550_fifo_tx_flush(vdev);
>
> spin_unlock(&vdev->lock);
> diff --git a/xen/drivers/passthrough/x86/hvm.c
> b/xen/drivers/passthrough/x86/hvm.c
> index a2ca7e0e570c..22905cd86f95 100644
> --- a/xen/drivers/passthrough/x86/hvm.c
> +++ b/xen/drivers/passthrough/x86/hvm.c
> @@ -924,12 +924,11 @@ static void hvm_gsi_eoi(struct domain *d, unsigned int
> gsi)
> {
> struct pirq *pirq = pirq_info(d, gsi);
>
> - /* Check if GSI is actually mapped. */
> - if ( !pirq_dpci(pirq) )
> - return;
> -
> hvm_gsi_deassert(d, gsi);
> - hvm_pirq_eoi(pirq);
> +
> + /* Check if GSI is actually mapped. */
> + if ( pirq_dpci(pirq) )
> + hvm_pirq_eoi(pirq);
> }
>
> static int cf_check _hvm_dpci_isairq_eoi(
> --
> 2.34.1
>
>
