Re: [Xen-devel] [RFC 07/16] xen/arm: p2m: Introduce p2m_is_valid and use it
On Tue, 30 Oct 2018, Julien Grall wrote: > Hi, > > On 30/10/2018 00:21, Stefano Stabellini wrote: > > On Mon, 8 Oct 2018, Julien Grall wrote: > > > The LPAE format allows to store information in an entry even with the > > > valid bit unset. In a follow-up patch, we will take advantage of this > > > feature to re-purpose the valid bit for generating a translation fault > > > even if an entry contains valid information. > > > > > > So we need a different way to know whether an entry contains valid > > > information. It is possible to use the information hold in the p2m_type > > > to know for that purpose. Indeed all entries containing valid > > > information will have a valid p2m type (i.e p2m_type != p2m_invalid). > > > > > > This patch introduces a new helper p2m_is_valid, which implements that > > > idea, and replace most of lpae_is_valid call with the new helper. The ones > > > remaining are for TLBs handling and entries accounting. > > > > > > With the renaming there are 2 others changes required: > > > - Generate table entry with a valid p2m type > > > - Detect new mapping for proper stats accounting > > > > > > Signed-off-by: Julien Grall > > > --- > > > xen/arch/arm/p2m.c | 34 +++--- > > > 1 file changed, 23 insertions(+), 11 deletions(-) > > > > > > diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c > > > index 6c76298ebc..2a1e7e9be2 100644 > > > --- a/xen/arch/arm/p2m.c > > > +++ b/xen/arch/arm/p2m.c > > > @@ -220,17 +220,26 @@ static p2m_access_t p2m_mem_access_radix_get(struct > > > p2m_domain *p2m, gfn_t gfn) > > > } > > > /* > > > + * In the case of the P2M, the valid bit is used for other purpose. Use > > > + * the type to check whether an entry is valid. > > > + */ > > > +static inline bool p2m_is_valid(lpae_t pte) > > > +{ > > > +return pte.p2m.type != p2m_invalid; > > > +} > > > + > > > +/* > > >* lpae_is_* helpers don't check whether the valid bit is set in the > > >* PTE. Provide our own overlay to check the valid bit. > > >*/ > > > static inline bool p2m_is_mapping(lpae_t pte, unsigned int level) > > > { > > > -return lpae_is_valid(pte) && lpae_is_mapping(pte, level); > > > +return p2m_is_valid(pte) && lpae_is_mapping(pte, level); > > > } > > > static inline bool p2m_is_superpage(lpae_t pte, unsigned int level) > > > { > > > -return lpae_is_valid(pte) && lpae_is_superpage(pte, level); > > > +return p2m_is_valid(pte) && lpae_is_superpage(pte, level); > > > } > > > #define GUEST_TABLE_MAP_FAILED 0 > > > @@ -264,7 +273,7 @@ static int p2m_next_level(struct p2m_domain *p2m, bool > > > read_only, > > > entry = *table + offset; > > > -if ( !lpae_is_valid(*entry) ) > > > +if ( !p2m_is_valid(*entry) ) > > > { > > > if ( read_only ) > > > return GUEST_TABLE_MAP_FAILED; > > > @@ -356,7 +365,7 @@ mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn, > > > entry = table[offsets[level]]; > > > -if ( lpae_is_valid(entry) ) > > > +if ( p2m_is_valid(entry) ) > > > { > > > *t = entry.p2m.type; > > > @@ -544,8 +553,11 @@ static lpae_t page_to_p2m_table(struct page_info > > > *page) > > > /* > > >* The access value does not matter because the hardware will ignore > > >* the permission fields for table entry. > > > + * > > > + * We use p2m_ram_rw so the entry has a valid type. This is important > > > + * for p2m_is_valid() to return valid on table entries. > > >*/ > > > -return mfn_to_p2m_entry(page_to_mfn(page), p2m_invalid, > > > p2m_access_rwx); > > > +return mfn_to_p2m_entry(page_to_mfn(page), p2m_ram_rw, > > > p2m_access_rwx); > > > } > > > static inline void p2m_write_pte(lpae_t *p, lpae_t pte, bool > > > clean_pte) > > > @@ -569,7 +581,7 @@ static int p2m_create_table(struct p2m_domain *p2m, > > > lpae_t *entry) > > > struct page_info *page; > > > lpae_t *p; > > > -ASSERT(!lpae_is_valid(*entry)); > > > +ASSERT(!p2m_is_valid(*entry)); > > > page = alloc_domheap_page(NULL, 0); > > > if ( page == NULL ) > > > @@ -626,7 +638,7 @@ static int p2m_mem_access_radix_set(struct p2m_domain > > > *p2m, gfn_t gfn, > > >*/ > > > static void p2m_put_l3_page(const lpae_t pte) > > > { > > > -ASSERT(lpae_is_valid(pte)); > > > +ASSERT(p2m_is_valid(pte)); > > > /* > > >* TODO: Handle other p2m types > > > @@ -654,11 +666,11 @@ static void p2m_free_entry(struct p2m_domain *p2m, > > > struct page_info *pg; > > > /* Nothing to do if the entry is invalid. */ > > > -if ( !lpae_is_valid(entry) ) > > > +if ( !p2m_is_valid(entry) ) > > > return; > > > /* Nothing to do but updating the stats if the entry is a > > > super-page. */ > > > -if ( p2m_is_superpage(entry, level) ) > > > +if ( level == 3 && entry.p2m.table ) > > > > Why? > > Because p2m_is_superpage(...)
Re: [Xen-devel] [RFC 07/16] xen/arm: p2m: Introduce p2m_is_valid and use it
Hi, On 30/10/2018 00:21, Stefano Stabellini wrote: On Mon, 8 Oct 2018, Julien Grall wrote: The LPAE format allows to store information in an entry even with the valid bit unset. In a follow-up patch, we will take advantage of this feature to re-purpose the valid bit for generating a translation fault even if an entry contains valid information. So we need a different way to know whether an entry contains valid information. It is possible to use the information hold in the p2m_type to know for that purpose. Indeed all entries containing valid information will have a valid p2m type (i.e p2m_type != p2m_invalid). This patch introduces a new helper p2m_is_valid, which implements that idea, and replace most of lpae_is_valid call with the new helper. The ones remaining are for TLBs handling and entries accounting. With the renaming there are 2 others changes required: - Generate table entry with a valid p2m type - Detect new mapping for proper stats accounting Signed-off-by: Julien Grall --- xen/arch/arm/p2m.c | 34 +++--- 1 file changed, 23 insertions(+), 11 deletions(-) diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c index 6c76298ebc..2a1e7e9be2 100644 --- a/xen/arch/arm/p2m.c +++ b/xen/arch/arm/p2m.c @@ -220,17 +220,26 @@ static p2m_access_t p2m_mem_access_radix_get(struct p2m_domain *p2m, gfn_t gfn) } /* + * In the case of the P2M, the valid bit is used for other purpose. Use + * the type to check whether an entry is valid. + */ +static inline bool p2m_is_valid(lpae_t pte) +{ +return pte.p2m.type != p2m_invalid; +} + +/* * lpae_is_* helpers don't check whether the valid bit is set in the * PTE. Provide our own overlay to check the valid bit. */ static inline bool p2m_is_mapping(lpae_t pte, unsigned int level) { -return lpae_is_valid(pte) && lpae_is_mapping(pte, level); +return p2m_is_valid(pte) && lpae_is_mapping(pte, level); } static inline bool p2m_is_superpage(lpae_t pte, unsigned int level) { -return lpae_is_valid(pte) && lpae_is_superpage(pte, level); +return p2m_is_valid(pte) && lpae_is_superpage(pte, level); } #define GUEST_TABLE_MAP_FAILED 0 @@ -264,7 +273,7 @@ static int p2m_next_level(struct p2m_domain *p2m, bool read_only, entry = *table + offset; -if ( !lpae_is_valid(*entry) ) +if ( !p2m_is_valid(*entry) ) { if ( read_only ) return GUEST_TABLE_MAP_FAILED; @@ -356,7 +365,7 @@ mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn, entry = table[offsets[level]]; -if ( lpae_is_valid(entry) ) +if ( p2m_is_valid(entry) ) { *t = entry.p2m.type; @@ -544,8 +553,11 @@ static lpae_t page_to_p2m_table(struct page_info *page) /* * The access value does not matter because the hardware will ignore * the permission fields for table entry. + * + * We use p2m_ram_rw so the entry has a valid type. This is important + * for p2m_is_valid() to return valid on table entries. */ -return mfn_to_p2m_entry(page_to_mfn(page), p2m_invalid, p2m_access_rwx); +return mfn_to_p2m_entry(page_to_mfn(page), p2m_ram_rw, p2m_access_rwx); } static inline void p2m_write_pte(lpae_t *p, lpae_t pte, bool clean_pte) @@ -569,7 +581,7 @@ static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry) struct page_info *page; lpae_t *p; -ASSERT(!lpae_is_valid(*entry)); +ASSERT(!p2m_is_valid(*entry)); page = alloc_domheap_page(NULL, 0); if ( page == NULL ) @@ -626,7 +638,7 @@ static int p2m_mem_access_radix_set(struct p2m_domain *p2m, gfn_t gfn, */ static void p2m_put_l3_page(const lpae_t pte) { -ASSERT(lpae_is_valid(pte)); +ASSERT(p2m_is_valid(pte)); /* * TODO: Handle other p2m types @@ -654,11 +666,11 @@ static void p2m_free_entry(struct p2m_domain *p2m, struct page_info *pg; /* Nothing to do if the entry is invalid. */ -if ( !lpae_is_valid(entry) ) +if ( !p2m_is_valid(entry) ) return; /* Nothing to do but updating the stats if the entry is a super-page. */ -if ( p2m_is_superpage(entry, level) ) +if ( level == 3 && entry.p2m.table ) Why? Because p2m_is_superpage(...) contains p2m_is_valid(). So we would test twice the validity of the p2m. But I guess this is not a big deal, so I can remove it. { p2m->stats.mappings[level]--; return; @@ -951,7 +963,7 @@ static int __p2m_set_entry(struct p2m_domain *p2m, else p2m->need_flush = true; } -else /* new mapping */ +else if ( !p2m_is_valid(orig_pte) ) /* new mapping */ There are a couple of lpae_is_valid checks just above this line that you missed, why haven't you changed them? If you have a good reason, please explain in a comment and/or commit message. This is already explained in the commit message: "This patch
Re: [Xen-devel] [RFC 07/16] xen/arm: p2m: Introduce p2m_is_valid and use it
On Mon, 8 Oct 2018, Julien Grall wrote: > The LPAE format allows to store information in an entry even with the > valid bit unset. In a follow-up patch, we will take advantage of this > feature to re-purpose the valid bit for generating a translation fault > even if an entry contains valid information. > > So we need a different way to know whether an entry contains valid > information. It is possible to use the information hold in the p2m_type > to know for that purpose. Indeed all entries containing valid > information will have a valid p2m type (i.e p2m_type != p2m_invalid). > > This patch introduces a new helper p2m_is_valid, which implements that > idea, and replace most of lpae_is_valid call with the new helper. The ones > remaining are for TLBs handling and entries accounting. > > With the renaming there are 2 others changes required: > - Generate table entry with a valid p2m type > - Detect new mapping for proper stats accounting > > Signed-off-by: Julien Grall > --- > xen/arch/arm/p2m.c | 34 +++--- > 1 file changed, 23 insertions(+), 11 deletions(-) > > diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c > index 6c76298ebc..2a1e7e9be2 100644 > --- a/xen/arch/arm/p2m.c > +++ b/xen/arch/arm/p2m.c > @@ -220,17 +220,26 @@ static p2m_access_t p2m_mem_access_radix_get(struct > p2m_domain *p2m, gfn_t gfn) > } > > /* > + * In the case of the P2M, the valid bit is used for other purpose. Use > + * the type to check whether an entry is valid. > + */ > +static inline bool p2m_is_valid(lpae_t pte) > +{ > +return pte.p2m.type != p2m_invalid; > +} > + > +/* > * lpae_is_* helpers don't check whether the valid bit is set in the > * PTE. Provide our own overlay to check the valid bit. > */ > static inline bool p2m_is_mapping(lpae_t pte, unsigned int level) > { > -return lpae_is_valid(pte) && lpae_is_mapping(pte, level); > +return p2m_is_valid(pte) && lpae_is_mapping(pte, level); > } > > static inline bool p2m_is_superpage(lpae_t pte, unsigned int level) > { > -return lpae_is_valid(pte) && lpae_is_superpage(pte, level); > +return p2m_is_valid(pte) && lpae_is_superpage(pte, level); > } > > #define GUEST_TABLE_MAP_FAILED 0 > @@ -264,7 +273,7 @@ static int p2m_next_level(struct p2m_domain *p2m, bool > read_only, > > entry = *table + offset; > > -if ( !lpae_is_valid(*entry) ) > +if ( !p2m_is_valid(*entry) ) > { > if ( read_only ) > return GUEST_TABLE_MAP_FAILED; > @@ -356,7 +365,7 @@ mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn, > > entry = table[offsets[level]]; > > -if ( lpae_is_valid(entry) ) > +if ( p2m_is_valid(entry) ) > { > *t = entry.p2m.type; > > @@ -544,8 +553,11 @@ static lpae_t page_to_p2m_table(struct page_info *page) > /* > * The access value does not matter because the hardware will ignore > * the permission fields for table entry. > + * > + * We use p2m_ram_rw so the entry has a valid type. This is important > + * for p2m_is_valid() to return valid on table entries. > */ > -return mfn_to_p2m_entry(page_to_mfn(page), p2m_invalid, p2m_access_rwx); > +return mfn_to_p2m_entry(page_to_mfn(page), p2m_ram_rw, p2m_access_rwx); > } > > static inline void p2m_write_pte(lpae_t *p, lpae_t pte, bool clean_pte) > @@ -569,7 +581,7 @@ static int p2m_create_table(struct p2m_domain *p2m, > lpae_t *entry) > struct page_info *page; > lpae_t *p; > > -ASSERT(!lpae_is_valid(*entry)); > +ASSERT(!p2m_is_valid(*entry)); > > page = alloc_domheap_page(NULL, 0); > if ( page == NULL ) > @@ -626,7 +638,7 @@ static int p2m_mem_access_radix_set(struct p2m_domain > *p2m, gfn_t gfn, > */ > static void p2m_put_l3_page(const lpae_t pte) > { > -ASSERT(lpae_is_valid(pte)); > +ASSERT(p2m_is_valid(pte)); > > /* > * TODO: Handle other p2m types > @@ -654,11 +666,11 @@ static void p2m_free_entry(struct p2m_domain *p2m, > struct page_info *pg; > > /* Nothing to do if the entry is invalid. */ > -if ( !lpae_is_valid(entry) ) > +if ( !p2m_is_valid(entry) ) > return; > > /* Nothing to do but updating the stats if the entry is a super-page. */ > -if ( p2m_is_superpage(entry, level) ) > +if ( level == 3 && entry.p2m.table ) Why? > { > p2m->stats.mappings[level]--; > return; > @@ -951,7 +963,7 @@ static int __p2m_set_entry(struct p2m_domain *p2m, > else > p2m->need_flush = true; > } > -else /* new mapping */ > +else if ( !p2m_is_valid(orig_pte) ) /* new mapping */ There are a couple of lpae_is_valid checks just above this line that you missed, why haven't you changed them? If you have a good reason, please explain in a comment and/or commit message. > p2m->stats.mappings[level]++; > > p2m_write_pte(entry, pte, p2m->clean_pte); >
[Xen-devel] [RFC 07/16] xen/arm: p2m: Introduce p2m_is_valid and use it
The LPAE format allows to store information in an entry even with the valid bit unset. In a follow-up patch, we will take advantage of this feature to re-purpose the valid bit for generating a translation fault even if an entry contains valid information. So we need a different way to know whether an entry contains valid information. It is possible to use the information hold in the p2m_type to know for that purpose. Indeed all entries containing valid information will have a valid p2m type (i.e p2m_type != p2m_invalid). This patch introduces a new helper p2m_is_valid, which implements that idea, and replace most of lpae_is_valid call with the new helper. The ones remaining are for TLBs handling and entries accounting. With the renaming there are 2 others changes required: - Generate table entry with a valid p2m type - Detect new mapping for proper stats accounting Signed-off-by: Julien Grall --- xen/arch/arm/p2m.c | 34 +++--- 1 file changed, 23 insertions(+), 11 deletions(-) diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c index 6c76298ebc..2a1e7e9be2 100644 --- a/xen/arch/arm/p2m.c +++ b/xen/arch/arm/p2m.c @@ -220,17 +220,26 @@ static p2m_access_t p2m_mem_access_radix_get(struct p2m_domain *p2m, gfn_t gfn) } /* + * In the case of the P2M, the valid bit is used for other purpose. Use + * the type to check whether an entry is valid. + */ +static inline bool p2m_is_valid(lpae_t pte) +{ +return pte.p2m.type != p2m_invalid; +} + +/* * lpae_is_* helpers don't check whether the valid bit is set in the * PTE. Provide our own overlay to check the valid bit. */ static inline bool p2m_is_mapping(lpae_t pte, unsigned int level) { -return lpae_is_valid(pte) && lpae_is_mapping(pte, level); +return p2m_is_valid(pte) && lpae_is_mapping(pte, level); } static inline bool p2m_is_superpage(lpae_t pte, unsigned int level) { -return lpae_is_valid(pte) && lpae_is_superpage(pte, level); +return p2m_is_valid(pte) && lpae_is_superpage(pte, level); } #define GUEST_TABLE_MAP_FAILED 0 @@ -264,7 +273,7 @@ static int p2m_next_level(struct p2m_domain *p2m, bool read_only, entry = *table + offset; -if ( !lpae_is_valid(*entry) ) +if ( !p2m_is_valid(*entry) ) { if ( read_only ) return GUEST_TABLE_MAP_FAILED; @@ -356,7 +365,7 @@ mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn, entry = table[offsets[level]]; -if ( lpae_is_valid(entry) ) +if ( p2m_is_valid(entry) ) { *t = entry.p2m.type; @@ -544,8 +553,11 @@ static lpae_t page_to_p2m_table(struct page_info *page) /* * The access value does not matter because the hardware will ignore * the permission fields for table entry. + * + * We use p2m_ram_rw so the entry has a valid type. This is important + * for p2m_is_valid() to return valid on table entries. */ -return mfn_to_p2m_entry(page_to_mfn(page), p2m_invalid, p2m_access_rwx); +return mfn_to_p2m_entry(page_to_mfn(page), p2m_ram_rw, p2m_access_rwx); } static inline void p2m_write_pte(lpae_t *p, lpae_t pte, bool clean_pte) @@ -569,7 +581,7 @@ static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry) struct page_info *page; lpae_t *p; -ASSERT(!lpae_is_valid(*entry)); +ASSERT(!p2m_is_valid(*entry)); page = alloc_domheap_page(NULL, 0); if ( page == NULL ) @@ -626,7 +638,7 @@ static int p2m_mem_access_radix_set(struct p2m_domain *p2m, gfn_t gfn, */ static void p2m_put_l3_page(const lpae_t pte) { -ASSERT(lpae_is_valid(pte)); +ASSERT(p2m_is_valid(pte)); /* * TODO: Handle other p2m types @@ -654,11 +666,11 @@ static void p2m_free_entry(struct p2m_domain *p2m, struct page_info *pg; /* Nothing to do if the entry is invalid. */ -if ( !lpae_is_valid(entry) ) +if ( !p2m_is_valid(entry) ) return; /* Nothing to do but updating the stats if the entry is a super-page. */ -if ( p2m_is_superpage(entry, level) ) +if ( level == 3 && entry.p2m.table ) { p2m->stats.mappings[level]--; return; @@ -951,7 +963,7 @@ static int __p2m_set_entry(struct p2m_domain *p2m, else p2m->need_flush = true; } -else /* new mapping */ +else if ( !p2m_is_valid(orig_pte) ) /* new mapping */ p2m->stats.mappings[level]++; p2m_write_pte(entry, pte, p2m->clean_pte); @@ -965,7 +977,7 @@ static int __p2m_set_entry(struct p2m_domain *p2m, * Free the entry only if the original pte was valid and the base * is different (to avoid freeing when permission is changed). */ -if ( lpae_is_valid(orig_pte) && +if ( p2m_is_valid(orig_pte) && !mfn_eq(lpae_get_mfn(*entry), lpae_get_mfn(orig_pte)) ) p2m_free_entry(p2m, orig_pte, level); -- 2.11.0 ___ Xen-devel mailing list