| Message ID | 20190614175144.20046-7-julien.grall@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | xen/arm: Provide a generic function to update Xen PT | expand |
On Fri, 14 Jun 2019, Julien Grall wrote: > Currently, the virtual address of the 3rd level page-tables is obtained > using mfn_to_virt(). > > On Arm32, mfn_to_virt can only work on xenheap page. While in theory > all the page-tables updated will reside in xenheap, in practice the > page-tables covering Xen memory (e.g xen_mapping) is part of Xen binary. > > Furthermore, a follow-up change will update xen_pt_update_entry() to > walk all the levels and therefore be more generic. Some of the > page-tables will also part of Xen memory and therefore will not be > reachable using mfn_to_virt(). > > The easiest way to reach those pages is to use {, un}map_domain_page(). > While on arm32 this means an extra mapping in the normal cases, this is not > very important as xen page-tables are not updated often. > > In order to allow future change in the way Xen page-tables are mapped, > two new helpers are introduced to map/unmap the page-tables. > > Signed-off-by: Julien Grall <julien.grall@arm.com> > Reviewed-by: Andrii Anisov <andrii_anisov@epam.com> > > --- > Changes in v3: > - Fix typo in the commit message > - Add Stefano's acked-by It didn't stick, so: Acked-by: Stefano Stabellini <sstabellini@kernel.org> :-) > > Changes in v2: > - Add Andrii's reviewed-by > --- > xen/arch/arm/mm.c | 26 ++++++++++++++++++++++---- > 1 file changed, 22 insertions(+), 4 deletions(-) > > diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c > index 3f6d0e29d5..c3dd2c08ba 100644 > --- a/xen/arch/arm/mm.c > +++ b/xen/arch/arm/mm.c > @@ -947,6 +947,16 @@ static int create_xen_table(lpae_t *entry) > return 0; > } > > +static lpae_t *xen_map_table(mfn_t mfn) > +{ > + return map_domain_page(mfn); > +} > + > +static void xen_unmap_table(const lpae_t *table) > +{ > + unmap_domain_page(table); > +} > + > /* Sanity check of the entry */ > static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int flags) > { > @@ -1016,6 +1026,7 @@ static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int flags) > static int xen_pt_update_entry(unsigned long addr, mfn_t mfn, > unsigned int flags) > { > + int rc; > lpae_t pte, *entry; > lpae_t *third = NULL; > > @@ -1034,15 +1045,17 @@ static int xen_pt_update_entry(unsigned long addr, mfn_t mfn, > > BUG_ON(!lpae_is_valid(*entry)); > > - third = mfn_to_virt(lpae_get_mfn(*entry)); > + third = xen_map_table(lpae_get_mfn(*entry)); > entry = &third[third_table_offset(addr)]; > > + rc = -EINVAL; > if ( !xen_pt_check_entry(*entry, mfn, flags) ) > - return -EINVAL; > + goto out; > > /* If we are only populating page-table, then we are done. */ > + rc = 0; > if ( flags & _PAGE_POPULATE ) > - return 0; > + goto out; > > /* We are removing the page */ > if ( !(flags & _PAGE_PRESENT) ) > @@ -1067,7 +1080,12 @@ static int xen_pt_update_entry(unsigned long addr, mfn_t mfn, > > write_pte(entry, pte); > > - return 0; > + rc = 0; > + > +out: > + xen_unmap_table(third); > + > + return rc; > } > > static DEFINE_SPINLOCK(xen_pt_lock); > -- > 2.11.0 >
Hi Stefano, On 6/14/19 10:00 PM, Stefano Stabellini wrote: > On Fri, 14 Jun 2019, Julien Grall wrote: >> Currently, the virtual address of the 3rd level page-tables is obtained >> using mfn_to_virt(). >> >> On Arm32, mfn_to_virt can only work on xenheap page. While in theory >> all the page-tables updated will reside in xenheap, in practice the >> page-tables covering Xen memory (e.g xen_mapping) is part of Xen binary. >> >> Furthermore, a follow-up change will update xen_pt_update_entry() to >> walk all the levels and therefore be more generic. Some of the >> page-tables will also part of Xen memory and therefore will not be >> reachable using mfn_to_virt(). >> >> The easiest way to reach those pages is to use {, un}map_domain_page(). >> While on arm32 this means an extra mapping in the normal cases, this is not >> very important as xen page-tables are not updated often. >> >> In order to allow future change in the way Xen page-tables are mapped, >> two new helpers are introduced to map/unmap the page-tables. >> >> Signed-off-by: Julien Grall <julien.grall@arm.com> >> Reviewed-by: Andrii Anisov <andrii_anisov@epam.com> >> >> --- >> Changes in v3: >> - Fix typo in the commit message >> - Add Stefano's acked-by > > It didn't stick, so: > > Acked-by: Stefano Stabellini <sstabellini@kernel.org> > > :-) Whoops yes. Thankfully I didn't add an ack by mistake this time :). Cheers,
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c index 3f6d0e29d5..c3dd2c08ba 100644 --- a/xen/arch/arm/mm.c +++ b/xen/arch/arm/mm.c @@ -947,6 +947,16 @@ static int create_xen_table(lpae_t *entry) return 0; } +static lpae_t *xen_map_table(mfn_t mfn) +{ + return map_domain_page(mfn); +} + +static void xen_unmap_table(const lpae_t *table) +{ + unmap_domain_page(table); +} + /* Sanity check of the entry */ static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int flags) { @@ -1016,6 +1026,7 @@ static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int flags) static int xen_pt_update_entry(unsigned long addr, mfn_t mfn, unsigned int flags) { + int rc; lpae_t pte, *entry; lpae_t *third = NULL; @@ -1034,15 +1045,17 @@ static int xen_pt_update_entry(unsigned long addr, mfn_t mfn, BUG_ON(!lpae_is_valid(*entry)); - third = mfn_to_virt(lpae_get_mfn(*entry)); + third = xen_map_table(lpae_get_mfn(*entry)); entry = &third[third_table_offset(addr)]; + rc = -EINVAL; if ( !xen_pt_check_entry(*entry, mfn, flags) ) - return -EINVAL; + goto out; /* If we are only populating page-table, then we are done. */ + rc = 0; if ( flags & _PAGE_POPULATE ) - return 0; + goto out; /* We are removing the page */ if ( !(flags & _PAGE_PRESENT) ) @@ -1067,7 +1080,12 @@ static int xen_pt_update_entry(unsigned long addr, mfn_t mfn, write_pte(entry, pte); - return 0; + rc = 0; + +out: + xen_unmap_table(third); + + return rc; } static DEFINE_SPINLOCK(xen_pt_lock);
Currently, the virtual address of the 3rd level page-tables is obtained using mfn_to_virt(). On Arm32, mfn_to_virt can only work on xenheap page. While in theory all the page-tables updated will reside in xenheap, in practice the page-tables covering Xen memory (e.g xen_mapping) is part of Xen binary. Furthermore, a follow-up change will update xen_pt_update_entry() to walk all the levels and therefore be more generic. Some of the page-tables will also part of Xen memory and therefore will not be reachable using mfn_to_virt(). The easiest way to reach those pages is to use {, un}map_domain_page(). While on arm32 this means an extra mapping in the normal cases, this is not very important as xen page-tables are not updated often. In order to allow future change in the way Xen page-tables are mapped, two new helpers are introduced to map/unmap the page-tables. Signed-off-by: Julien Grall <julien.grall@arm.com> Reviewed-by: Andrii Anisov <andrii_anisov@epam.com> --- Changes in v3: - Fix typo in the commit message - Add Stefano's acked-by Changes in v2: - Add Andrii's reviewed-by --- xen/arch/arm/mm.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-)