| Message ID | 20210226105640.12037-3-julien@xen.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen/iommu: Collection of bug fixes for IOMMU teardown | expand |
On 26.02.2021 11:56, Julien Grall wrote: > From: Julien Grall <jgrall@amazon.com> > > The new x86 IOMMU page-tables allocator will release the pages when > relinquishing the domain resources. However, this is not sufficient > when the domain is dying because nothing prevents page-table to be > allocated. > > As the domain is dying, it is not necessary to continue to modify the > IOMMU page-tables as they are going to be destroyed soon. > > At the moment, page-table allocates will only happen when iommu_map(). > So after this change there will be no more page-table allocation > happening because we don't use superpage mappings yet when not sharing > page tables. > > In order to observe d->is_dying correctly, we need to rely on per-arch > locking, so the check to ignore IOMMU mapping is added on the per-driver > map_page() callback. > > Signed-off-by: Julien Grall <jgrall@amazon.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Does this also want a Fixes: tag (the same as patch 1)? Jan
> From: Julien Grall <julien@xen.org> > Sent: Friday, February 26, 2021 6:57 PM > > From: Julien Grall <jgrall@amazon.com> > > The new x86 IOMMU page-tables allocator will release the pages when > relinquishing the domain resources. However, this is not sufficient > when the domain is dying because nothing prevents page-table to be > allocated. > > As the domain is dying, it is not necessary to continue to modify the > IOMMU page-tables as they are going to be destroyed soon. > > At the moment, page-table allocates will only happen when iommu_map(). > So after this change there will be no more page-table allocation > happening because we don't use superpage mappings yet when not sharing > page tables. > > In order to observe d->is_dying correctly, we need to rely on per-arch > locking, so the check to ignore IOMMU mapping is added on the per-driver > map_page() callback. > > Signed-off-by: Julien Grall <jgrall@amazon.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> > > --- > > As discussed in v3, this is only covering 4.15. We can discuss > post-4.15 how to catch page-table allocations if another caller (e.g. > iommu_unmap() if we ever decide to support superpages) start to use the > page-table allocator. > > Changes in v5: > - Clarify in the commit message why fixing iommu_map() is enough > - Split "if ( !is_iommu_enabled(d) )" in a separate patch > - Update the comment on top of the spin_barrier() > > Changes in v4: > - Move the patch to the top of the queue > - Reword the commit message > > Changes in v3: > - Patch added. This is a replacement of "xen/iommu: iommu_map: Don't > crash the domain if it is dying" > --- > xen/drivers/passthrough/amd/iommu_map.c | 12 ++++++++++++ > xen/drivers/passthrough/vtd/iommu.c | 12 ++++++++++++ > xen/drivers/passthrough/x86/iommu.c | 3 +++ > 3 files changed, 27 insertions(+) > > diff --git a/xen/drivers/passthrough/amd/iommu_map.c > b/xen/drivers/passthrough/amd/iommu_map.c > index d3a8b1aec766..560af54b765b 100644 > --- a/xen/drivers/passthrough/amd/iommu_map.c > +++ b/xen/drivers/passthrough/amd/iommu_map.c > @@ -285,6 +285,18 @@ int amd_iommu_map_page(struct domain *d, dfn_t > dfn, mfn_t mfn, > > spin_lock(&hd->arch.mapping_lock); > > + /* > + * IOMMU mapping request can be safely ignored when the domain is > dying. > + * > + * hd->arch.mapping_lock guarantees that d->is_dying will be observed > + * before any page tables are freed (see iommu_free_pgtables()). > + */ > + if ( d->is_dying ) > + { > + spin_unlock(&hd->arch.mapping_lock); > + return 0; > + } > + > rc = amd_iommu_alloc_root(d); > if ( rc ) > { > diff --git a/xen/drivers/passthrough/vtd/iommu.c > b/xen/drivers/passthrough/vtd/iommu.c > index d136fe36883b..b549a71530d5 100644 > --- a/xen/drivers/passthrough/vtd/iommu.c > +++ b/xen/drivers/passthrough/vtd/iommu.c > @@ -1762,6 +1762,18 @@ static int __must_check > intel_iommu_map_page(struct domain *d, dfn_t dfn, > > spin_lock(&hd->arch.mapping_lock); > > + /* > + * IOMMU mapping request can be safely ignored when the domain is > dying. > + * > + * hd->arch.mapping_lock guarantees that d->is_dying will be observed > + * before any page tables are freed (see iommu_free_pgtables()) > + */ > + if ( d->is_dying ) > + { > + spin_unlock(&hd->arch.mapping_lock); > + return 0; > + } > + > pg_maddr = addr_to_dma_page_maddr(d, dfn_to_daddr(dfn), 1); > if ( !pg_maddr ) > { > diff --git a/xen/drivers/passthrough/x86/iommu.c > b/xen/drivers/passthrough/x86/iommu.c > index 58a330e82247..ad19b7dd461c 100644 > --- a/xen/drivers/passthrough/x86/iommu.c > +++ b/xen/drivers/passthrough/x86/iommu.c > @@ -270,6 +270,9 @@ int iommu_free_pgtables(struct domain *d) > if ( !is_iommu_enabled(d) ) > return 0; > > + /* After this barrier, no new IOMMU mappings can be inserted. */ > + spin_barrier(&hd->arch.mapping_lock); > + > while ( (pg = page_list_remove_head(&hd->arch.pgtables.list)) ) > { > free_domheap_page(pg); > -- > 2.17.1
Hi Jan, On 26/02/2021 13:30, Jan Beulich wrote: > On 26.02.2021 11:56, Julien Grall wrote: >> From: Julien Grall <jgrall@amazon.com> >> >> The new x86 IOMMU page-tables allocator will release the pages when >> relinquishing the domain resources. However, this is not sufficient >> when the domain is dying because nothing prevents page-table to be >> allocated. >> >> As the domain is dying, it is not necessary to continue to modify the >> IOMMU page-tables as they are going to be destroyed soon. >> >> At the moment, page-table allocates will only happen when iommu_map(). >> So after this change there will be no more page-table allocation >> happening because we don't use superpage mappings yet when not sharing >> page tables. >> >> In order to observe d->is_dying correctly, we need to rely on per-arch >> locking, so the check to ignore IOMMU mapping is added on the per-driver >> map_page() callback. >> >> Signed-off-by: Julien Grall <jgrall@amazon.com> > > Reviewed-by: Jan Beulich <jbeulich@suse.com> Thanks! > > Does this also want a Fixes: tag (the same as patch 1)? I think so. I will add it when committing the series. Cheers,
diff --git a/xen/drivers/passthrough/amd/iommu_map.c b/xen/drivers/passthrough/amd/iommu_map.c index d3a8b1aec766..560af54b765b 100644 --- a/xen/drivers/passthrough/amd/iommu_map.c +++ b/xen/drivers/passthrough/amd/iommu_map.c @@ -285,6 +285,18 @@ int amd_iommu_map_page(struct domain *d, dfn_t dfn, mfn_t mfn, spin_lock(&hd->arch.mapping_lock); + /* + * IOMMU mapping request can be safely ignored when the domain is dying. + * + * hd->arch.mapping_lock guarantees that d->is_dying will be observed + * before any page tables are freed (see iommu_free_pgtables()). + */ + if ( d->is_dying ) + { + spin_unlock(&hd->arch.mapping_lock); + return 0; + } + rc = amd_iommu_alloc_root(d); if ( rc ) { diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c index d136fe36883b..b549a71530d5 100644 --- a/xen/drivers/passthrough/vtd/iommu.c +++ b/xen/drivers/passthrough/vtd/iommu.c @@ -1762,6 +1762,18 @@ static int __must_check intel_iommu_map_page(struct domain *d, dfn_t dfn, spin_lock(&hd->arch.mapping_lock); + /* + * IOMMU mapping request can be safely ignored when the domain is dying. + * + * hd->arch.mapping_lock guarantees that d->is_dying will be observed + * before any page tables are freed (see iommu_free_pgtables()) + */ + if ( d->is_dying ) + { + spin_unlock(&hd->arch.mapping_lock); + return 0; + } + pg_maddr = addr_to_dma_page_maddr(d, dfn_to_daddr(dfn), 1); if ( !pg_maddr ) { diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c index 58a330e82247..ad19b7dd461c 100644 --- a/xen/drivers/passthrough/x86/iommu.c +++ b/xen/drivers/passthrough/x86/iommu.c @@ -270,6 +270,9 @@ int iommu_free_pgtables(struct domain *d) if ( !is_iommu_enabled(d) ) return 0; + /* After this barrier, no new IOMMU mappings can be inserted. */ + spin_barrier(&hd->arch.mapping_lock); + while ( (pg = page_list_remove_head(&hd->arch.pgtables.list)) ) { free_domheap_page(pg);