RE: [PATCH v2 08/10] remove remaining uses of iommu_legacy_map/unmap

From: "Durrant, Paul" <pdurrant@amazon.co.uk>
To: Paul Durrant <paul@xen.org>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "Kevin Tian" <kevin.tian@intel.com>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	"Julien Grall" <julien@xen.org>,
	"Jun Nakajima" <jun.nakajima@intel.com>, "Wei Liu" <wl@xen.org>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Ian Jackson" <ian.jackson@eu.citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Jan Beulich" <jbeulich@suse.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: RE: [PATCH v2 08/10] remove remaining uses of iommu_legacy_map/unmap
Date: Fri, 31 Jul 2020 09:21:58 +0000	[thread overview]
Message-ID: <ccd1e0d3ba334dc5b1ba37734f581b3b@EX13D32EUC003.ant.amazon.com> (raw)
In-Reply-To: <20200730142926.6051-9-paul@xen.org>

> -----Original Message-----
> From: Paul Durrant <paul@xen.org>
> Sent: 30 July 2020 15:29
> To: xen-devel@lists.xenproject.org
> Cc: Durrant, Paul <pdurrant@amazon.co.uk>; Jan Beulich <jbeulich@suse.com>; Andrew Cooper
> <andrew.cooper3@citrix.com>; Wei Liu <wl@xen.org>; Roger Pau Monné <roger.pau@citrix.com>; George
> Dunlap <george.dunlap@citrix.com>; Ian Jackson <ian.jackson@eu.citrix.com>; Julien Grall
> <julien@xen.org>; Stefano Stabellini <sstabellini@kernel.org>; Jun Nakajima <jun.nakajima@intel.com>;
> Kevin Tian <kevin.tian@intel.com>
> Subject: [EXTERNAL] [PATCH v2 08/10] remove remaining uses of iommu_legacy_map/unmap
> 
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> 
> 
> From: Paul Durrant <pdurrant@amazon.com>
> 
> The 'legacy' functions do implicit flushing so amend the callers to do the
> appropriate flushing.
> 
> Unfortunately, because of the structure of the P2M code, we cannot remove
> the per-CPU 'iommu_dont_flush_iotlb' global and the optimization it
> facilitates. It is now checked directly iommu_iotlb_flush(). Also, it is
> now declared as bool (rather than bool_t) and setting/clearing it are no
> longer pointlessly gated on is_iommu_enabled() returning true. (Arguably
> it is also pointless to gate the call to iommu_iotlb_flush() on that
> condition - since it is a no-op in that case - but the if clause allows
> the scope of a stack variable to be restricted).
> 
> NOTE: The code in memory_add() now fails if the number of pages passed to
>       a single call overflows an unsigned int. I don't believe this will
>       ever happen in practice.
> 
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>

I realise now that I completely forgot to address Jan's comments on grant table locking and flush batching, so there will be a v3 of at least this patch.

  Paul