Re: [PATCH v2 5/5] iommu/riscv: Allow RISC_VIOMMU to COMPILE_TEST

From: Jason Gunthorpe <jgg@nvidia.com>
To: Andrew Jones <andrew.jones@oss.qualcomm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>,
	Albert Ou <aou@eecs.berkeley.edu>,
	iommu@lists.linux.dev, Joerg Roedel <joro@8bytes.org>,
	linux-riscv@lists.infradead.org,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <pjw@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Tomasz Jeznach <tjeznach@rivosinc.com>,
	Will Deacon <will@kernel.org>,
	lihangjing@bytedance.com, Xu Lu <luxu.kernel@bytedance.com>,
	patches@lists.linux.dev, xieyongji@bytedance.com
Subject: Re: [PATCH v2 5/5] iommu/riscv: Allow RISC_VIOMMU to COMPILE_TEST
Date: Fri, 30 Jan 2026 19:44:34 -0400	[thread overview]
Message-ID: <20260130234434.GK2223369@nvidia.com> (raw)
In-Reply-To: <dn7bsft2qvjod3sm6omneq37pwr2jtdzgobapy6obpgccg7soc@ctvs3c2w4vob>

On Fri, Jan 30, 2026 at 01:58:51PM -0600, Andrew Jones wrote:
> >  config RISCV_IOMMU
> >  	bool "RISC-V IOMMU Support"
> > -	depends on RISCV && 64BIT
> > -	default y
> > +	default RISCV
> > +	depends on (RISCV || COMPILE_TEST) && 64BIT
> > +	depends on GENERIC_MSI_IRQ
> 
> This new depends isn't called out in the commit message. Maybe it should
> even be its own patch with a fixes d5f88acdd6ff ("iommu/riscv: Add support
> for platform msi") tag, but, either way, thanks for the fix.

I think if riscv has a 32 bit configuration with iommu HW available
then you'd want a different fix to make it work.. Probably include one
of the high/low headers to get emulated writeq

This is just intended to make it work with COMPILE_TEST on eg ARM32.

> > @@ -436,7 +436,9 @@ static unsigned int riscv_iommu_queue_send(struct riscv_iommu_queue *queue,
> >  	 * 6. Make sure the doorbell write to the device has finished before updating
> >  	 *    the shadow tail index in normal memory. 'fence o, w'
> >  	 */
> > +#ifdef CONFIG_MMIOWB
> >  	mmiowb();
> > +#endif
> 
> Taking inspiration from powerpc we'd put the #ifdef CONFIG_MMIOWB in
> arch/riscv/include/asm/mmiowb.h

That won't help compile on x86 for example.

Thanks,
Jason