| Message ID | 20180716172712.20294-5-julien.grall@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | xen/arm: Bunch of clean-up/improvement | expand |
On Mon, 16 Jul 2018, Julien Grall wrote: > The p2m lock is only necessary to prevent gvirt_to_maddr failing when > break-before-make sequence is used in the P2M update concurrently on > another pCPU. So reduce the locking section. > > Signed-off-by: Julien Grall <julien.grall@arm.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> > --- > > Note a newline has been dropped to keep the block together. > --- > xen/arch/arm/p2m.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c > index 14791388ad..5ca7ffe41b 100644 > --- a/xen/arch/arm/p2m.c > +++ b/xen/arch/arm/p2m.c > @@ -1415,9 +1415,13 @@ struct page_info *get_page_from_gva(struct vcpu *v, vaddr_t va, > if ( v != current ) > return NULL; > > + /* > + * The lock is here to protect us against the break-before-make > + * sequence used when updating the entry. > + */ > p2m_read_lock(p2m); > - > par = gvirt_to_maddr(va, &maddr, flags); > + p2m_read_unlock(p2m); > > if ( par ) > { > @@ -1445,8 +1449,6 @@ struct page_info *get_page_from_gva(struct vcpu *v, vaddr_t va, > } > > err: > - p2m_read_unlock(p2m); > - > if ( !page && p2m->mem_access_enabled ) > page = p2m_mem_access_check_and_get_page(va, flags, v); > > -- > 2.11.0 >
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c index 14791388ad..5ca7ffe41b 100644 --- a/xen/arch/arm/p2m.c +++ b/xen/arch/arm/p2m.c @@ -1415,9 +1415,13 @@ struct page_info *get_page_from_gva(struct vcpu *v, vaddr_t va, if ( v != current ) return NULL; + /* + * The lock is here to protect us against the break-before-make + * sequence used when updating the entry. + */ p2m_read_lock(p2m); - par = gvirt_to_maddr(va, &maddr, flags); + p2m_read_unlock(p2m); if ( par ) { @@ -1445,8 +1449,6 @@ struct page_info *get_page_from_gva(struct vcpu *v, vaddr_t va, } err: - p2m_read_unlock(p2m); - if ( !page && p2m->mem_access_enabled ) page = p2m_mem_access_check_and_get_page(va, flags, v);
The p2m lock is only necessary to prevent gvirt_to_maddr failing when break-before-make sequence is used in the P2M update concurrently on another pCPU. So reduce the locking section. Signed-off-by: Julien Grall <julien.grall@arm.com> --- Note a newline has been dropped to keep the block together. --- xen/arch/arm/p2m.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)