RE: [PATCH 2/8] iommu/arm-smmu-v3: Use S2FWB when available

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

> -----Original Message-----
> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Friday, August 9, 2024 4:12 PM
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
> Cc: acpica-devel@lists.linux.dev; Alex Williamson
> <alex.williamson@redhat.com>; Guohanjun (Hanjun Guo)
> <guohanjun@huawei.com>; iommu@lists.linux.dev; Joerg Roedel
> <joro@8bytes.org>; Kevin Tian <kevin.tian@intel.com>; kvm@vger.kernel.org;
> Len Brown <lenb@kernel.org>; linux-acpi@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; Lorenzo Pieralisi <lpieralisi@kernel.org>; Rafael J.
> Wysocki <rafael@kernel.org>; Robert Moore <robert.moore@intel.com>; Robin
> Murphy <robin.murphy@arm.com>; Sudeep Holla <sudeep.holla@arm.com>;
> Will Deacon <will@kernel.org>; Eric Auger <eric.auger@redhat.com>; Jean-
> Philippe Brucker <jean-philippe@linaro.org>; Moritz Fischer <mdf@kernel.org>;
> Michael Shavit <mshavit@google.com>; Nicolin Chen <nicolinc@nvidia.com>;
> patches@lists.linux.dev
> Subject: Re: [PATCH 2/8] iommu/arm-smmu-v3: Use S2FWB when available
> 
> On Fri, Aug 09, 2024 at 02:26:13PM +0000, Shameerali Kolothum Thodi wrote:
> > > +		if (smmu->features & ARM_SMMU_FEAT_S2FWB)
> > > +			pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_ARM_S2FWB;
> >
> > This probably requires an update in arm_64_lpae_alloc_pgtable_s2() quirks
> check.
> 
> Yep, fixed I was hoping you had HW to test this..

Let me see if I can get hold of a test setup that supports S2FWB.

I do have another concern with respect to the hardware we have which doesn't
support S2FWB, but those can claim CANWBS. The problem is, BIOS update is not
a very liked/feasible solution to already deployed ones. But we can probably add 
an option/quirk in SMMUv3 driver for those platforms(based on 
ACPI_IORT_SMMU_V3_HISILICON_HI161X).  I hope this is fine.

Thanks,
Shameer