Re: [Xen-devel] [PATCH] arm/dom0: Add check for maximum number of supported vGIC IRQs

[Lukas Jünger <lukas.juenger@xxxxxxxxxxxxxxxxxx>]

On 4/1/19 1:24 PM, Julien Grall wrote:
> Hi Lukas,
Hi,
> You sent this patch twice. Is there any difference between the two?
No, they are the same. I accidentally send it twice.
> On 3/27/19 7:19 AM, Lukas Juenger wrote:
> > Xen's vGIC implementation supports a maximum number of 992 IRQ lines.
> NIT:  The correct term is Interrupt Lines.
>
> > GICv2 specification allows for 1020 IRQ lines.
> This is common code, so we should also take into account the other GIC 
> versions we support.
>
>
> > This commit adds a check for this discrepancy.
> Your commit message should explain why reducing to 992 Interrupts lines 
> is fine. How about the following commit title and message?
> "xen/arm: Cap the number interrupts of lines for dom0
>
> Dom0 vGIC will use the same number interrupt lines as the hardware GIC. 
> While the hardware GIC can support up to 1019 interrupt lines, the vGIC 
> is only supporting up to 992 interrupt lines.
> This means Xen will not be able to boot on platform where the hardware 
> GIC supports more the 992 interrupt lines.
> While it would make sense to increase the limits in the vGICs, this is 
> not trivial because of the design choices.
> At the moment, only models seem to report the maximum of interrupt 
> lines. They also don't have any interrupt wired above the 992 limits.
> So this would be fine to cap the interrupt for Dom0 to 992 lines.
> "
>
> > Signed-off-by: Lukas Juenger (juenger@xxxxxxxxxxxxxxxxxx)
> We tend to encapsulate the e-mail between <...> and not (...).
I adapted the patch according to your suggestions above.
> > ---
> >   xen/arch/arm/setup.c | 8 +++++++-
> >   1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> > index 444857a967..37b3648a18 100644
> > --- a/xen/arch/arm/setup.c
> > +++ b/xen/arch/arm/setup.c
> > @@ -888,7 +888,13 @@ void __init start_xen(unsigned long 
> > boot_phys_offset,
> >       /* Create initial domain 0. */
> >       /* The vGIC for DOM0 is exactly emulating the hardware GIC */
> >       dom0_cfg.arch.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE;
> > -    dom0_cfg.arch.nr_spis = gic_number_lines() - 32;
> > +    /*
> > +     * Xen vGIC supports a maximum of 992 IRQ lines.
> > +     * 32 are substracted to cover local IRQs.
> > +     */
> > +    dom0_cfg.arch.nr_spis = min(gic_number_lines(), (unsigned int) 
> > 992) - 32;
> > +    if ( gic_number_lines() > 992 )
> > +        printk(XENLOG_WARNING "Maximum number of vGIC IRQs 
> > exceeded.\n");
> >       dom0_cfg.max_vcpus = dom0_max_vcpus();
> >       dom0 = domain_create(0, &dom0_cfg, true);
> Cheers,
Thanks for you input,
Lukas

Attachment: smime.p7s
Description: S/MIME Cryptographic Signature

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel