Re: [Xen-devel] [RFC v1 07/15] vt-d: Add API to update IRTE when VT-d PI is used

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 25/03/15 12:31, Feng Wu wrote:
> This patch adds an API which is used to update the IRTE
> for posted-interrupt when guest changes MSI/MSI-X information.
>
> Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> ---
>   xen/drivers/passthrough/vtd/intremap.c | 83 ++++++++++++++++++++++++++++++++++
>   xen/drivers/passthrough/vtd/iommu.h    |  3 ++
>   xen/include/asm-x86/iommu.h            |  2 +
>   3 files changed, 88 insertions(+)
>
> diff --git a/xen/drivers/passthrough/vtd/intremap.c 
> b/xen/drivers/passthrough/vtd/intremap.c
> index 0333686..f44e74d 100644
> --- a/xen/drivers/passthrough/vtd/intremap.c
> +++ b/xen/drivers/passthrough/vtd/intremap.c
> @@ -898,3 +898,86 @@ void iommu_disable_x2apic_IR(void)
>       for_each_drhd_unit ( drhd )
>           disable_qinval(drhd->iommu);
>   }
> +
> +/*
> + * This function is used to update the IRTE for posted-interrupt
> + * when guest changes MSI/MSI-X information
> + */
> +int pi_update_irte(struct vcpu *v, struct pirq *pirq, uint32_t gvec )
Stray space after gvec.

I presume gvec means "guest vector", in which case it should be a uint8_t.

> +{
> +    struct irq_desc *desc;
> +    struct msi_desc *msi_desc;
> +    int remap_index, rc = -1;
> +    struct pci_dev *pci_dev;
> +    struct acpi_drhd_unit *drhd;
> +    struct iommu *iommu;
> +    struct ir_ctrl *ir_ctrl;
> +    struct iremap_entry *iremap_entries = NULL, *p = NULL;
> +    struct iremap_entry new_ire;
> +    struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
> +    unsigned long flags;
> +
> +    desc = pirq_spin_lock_irq_desc(pirq, NULL);
> +    if ( !desc )
> +        return -1;
> +
> +    msi_desc = desc->msi_desc;
> +    if ( !msi_desc )
> +        goto unlock_out;
> +
> +    remap_index = msi_desc->remap_index;
> +    pci_dev = msi_desc->dev;
> +    if ( !pci_dev )
> +        goto unlock_out;
> +
> +    drhd = acpi_find_matched_drhd_unit(pci_dev);
This does an O(n^2) walk over the dhrd_units list and the unit 
device_cnt.  As the layout will be completely static, might it be better 
to stash drhd information in struct pci_dev during boot?
> +    if (!drhd)
Spaces inside brackets.

> +    {
> +        dprintk(XENLOG_INFO VTDPREFIX, "failed to get drhd!\n");
This is a useless error message, providing no useful information to 
identify the issue.
At the very least it should identify the domain and vcpu (%pv of v), the 
guest vector and pci device.  Also, drop the exclamation mark - it is 
not useful in the log.
> +        goto unlock_out;
> +    }
> +
> +    iommu = drhd->iommu;
> +    ir_ctrl = iommu_ir_ctrl(iommu);
> +    if ( !ir_ctrl )
> +    {
> +        dprintk(XENLOG_INFO VTDPREFIX, "failed to get ir_ctrl!\n");
Needs simiarly extending with some information.

> +        goto unlock_out;
> +    }
> +
> +    spin_lock_irqsave(&ir_ctrl->iremap_lock, flags);
> +
> +    GET_IREMAP_ENTRY(ir_ctrl->iremap_maddr, remap_index, iremap_entries, p);
> +
> +    memcpy(&new_ire, p, sizeof(struct iremap_entry));
sizeof(new_ire) please

> +
> +    /* Setup/Update interrupt remapping table entry */
> +    new_ire.lo_intpost.urg = 0;
> +    new_ire.lo_intpost.vector = gvec;
> +    new_ire.lo_intpost.pda_l = (((u64)virt_to_maddr(pi_desc)) >>
> +                                (32 - PDA_LOW_BIT)) & ~(-1UL << PDA_LOW_BIT);
> +    new_ire.hi_intpost.pda_h = (((u64)virt_to_maddr(pi_desc)) >>  32) &
> +                                ~(-1UL << PDA_HIGH_BIT);
Is it possible to hide this bit manipulation in side a static inline 
function which takes an ire and pi_desc pointer rather than open coding it?
> +
> +    new_ire.lo_intpost.res_1 = 0;
> +    new_ire.lo_intpost.res_2 = 0;
> +    new_ire.lo_intpost.res_3 = 0;
> +    new_ire.hi_intpost.res_1 = 0;
> +
> +    new_ire.lo_intpost.im = 1;
> +
> +    memcpy(p, &new_ire, sizeof(struct iremap_entry));
> +    iommu_flush_cache_entry(p, sizeof(struct iremap_entry));
Same here regarding sizeof.

Furthermore, is the memcpy() safe to update the live descriptor?

If it is, why do you not update the descriptor in place using p-> rather 
than copying it to the stack and back?
~Andrew

> +    iommu_flush_iec_index(iommu, 0, remap_index);
> +
> +    if ( iremap_entries )
> +        unmap_vtd_domain_page(iremap_entries);
> +
> +    spin_unlock_irqrestore(&ir_ctrl->iremap_lock, flags);
> +
> +    rc = 0;
> + unlock_out:
> +    spin_unlock_irq(&desc->lock);
> +
> +    return rc;
> +}
> diff --git a/xen/drivers/passthrough/vtd/iommu.h 
> b/xen/drivers/passthrough/vtd/iommu.h
> index cd61e12..ffa72c8 100644
> --- a/xen/drivers/passthrough/vtd/iommu.h
> +++ b/xen/drivers/passthrough/vtd/iommu.h
> @@ -334,6 +334,9 @@ struct iremap_entry {
>     };
>   };
>   
> +#define PDA_LOW_BIT    26
> +#define PDA_HIGH_BIT   32
> +
>   /* Max intr remapping table page order is 8, as max number of IRTEs is 64K */
>   #define IREMAP_PAGE_ORDER  8
>   
> diff --git a/xen/include/asm-x86/iommu.h b/xen/include/asm-x86/iommu.h
> index e7a65da..d233621 100644
> --- a/xen/include/asm-x86/iommu.h
> +++ b/xen/include/asm-x86/iommu.h
> @@ -32,6 +32,8 @@ int iommu_supports_eim(void);
>   int iommu_enable_x2apic_IR(void);
>   void iommu_disable_x2apic_IR(void);
>   
> +int pi_update_irte(struct vcpu *v, struct pirq *pirq, uint32_t gvec);
> +
>   #endif /* !__ARCH_X86_IOMMU_H__ */
>   /*
>    * Local variables:

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