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Re: [Xen-devel] [RFC 14/16] xen/arm: p2m: Extend p2m_get_entry to return the value of bit[0] (valid bit)
Hi Stefano,
On 05/11/2018 17:31, Stefano Stabellini wrote:
On Mon, 5 Nov 2018, Julien Grall wrote:
Hi Stefano,
On 02/11/2018 23:44, Stefano Stabellini wrote:
On Mon, 8 Oct 2018, Julien Grall wrote:
With the recent changes, a P2M entry may be populated but may as not
valid. In some situation, it would be useful to know whether the entry
has been marked available to guest in order to perform a specific
action. So extend p2m_get_entry to return the value of bit[0] (valid bit).
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
xen/arch/arm/mem_access.c | 6 +++---
xen/arch/arm/p2m.c | 20 ++++++++++++++++----
xen/include/asm-arm/p2m.h | 3 ++-
3 files changed, 21 insertions(+), 8 deletions(-)
diff --git a/xen/arch/arm/mem_access.c b/xen/arch/arm/mem_access.c
index 9239bdf323..f434510b2a 100644
--- a/xen/arch/arm/mem_access.c
+++ b/xen/arch/arm/mem_access.c
@@ -70,7 +70,7 @@ static int __p2m_get_mem_access(struct domain *d, gfn_t
gfn,
* No setting was found in the Radix tree. Check if the
* entry exists in the page-tables.
*/
- mfn_t mfn = p2m_get_entry(p2m, gfn, NULL, NULL, NULL);
+ mfn_t mfn = p2m_get_entry(p2m, gfn, NULL, NULL, NULL, NULL);
if ( mfn_eq(mfn, INVALID_MFN) )
return -ESRCH;
@@ -199,7 +199,7 @@ p2m_mem_access_check_and_get_page(vaddr_t gva,
unsigned long flag,
* We had a mem_access permission limiting the access, but the page
type
* could also be limiting, so we need to check that as well.
*/
- mfn = p2m_get_entry(p2m, gfn, &t, NULL, NULL);
+ mfn = p2m_get_entry(p2m, gfn, &t, NULL, NULL, NULL);
if ( mfn_eq(mfn, INVALID_MFN) )
goto err;
@@ -405,7 +405,7 @@ long p2m_set_mem_access(struct domain *d, gfn_t gfn,
uint32_t nr,
gfn = gfn_next_boundary(gfn, order) )
{
p2m_type_t t;
- mfn_t mfn = p2m_get_entry(p2m, gfn, &t, NULL, &order);
+ mfn_t mfn = p2m_get_entry(p2m, gfn, &t, NULL, &order, NULL);
if ( !mfn_eq(mfn, INVALID_MFN) )
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 12b459924b..df6b48d73b 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -306,10 +306,14 @@ static int p2m_next_level(struct p2m_domain *p2m,
bool read_only,
*
* If the entry is not present, INVALID_MFN will be returned and the
* page_order will be set according to the order of the invalid range.
+ *
+ * valid will contain the value of bit[0] (e.g valid bit) of the
+ * entry.
*/
mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn,
p2m_type_t *t, p2m_access_t *a,
- unsigned int *page_order)
+ unsigned int *page_order,
+ bool *valid)
{
paddr_t addr = gfn_to_gaddr(gfn);
unsigned int level = 0;
@@ -317,6 +321,7 @@ mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn,
int rc;
mfn_t mfn = INVALID_MFN;
p2m_type_t _t;
+ bool _valid;
/* Convenience aliases */
const unsigned int offsets[4] = {
@@ -334,6 +339,10 @@ mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t
gfn,
*t = p2m_invalid;
+ /* Allow valid to be NULL */
+ valid = valid?: &_valid;
+ *valid = false;
Why not a simple:
if ( valid )
*valid = false;
especially given that you do the same if ( valid ) check below.
In fact, it doesn' look like we need _valid?
I thought I dropped the if ( valid ) below. I would actually prefer to keep
_valid and avoid using if ( ... ) everywhere.
This makes the code slightly easier to follow.
_valid is a good trick, but I don't think is worth doing it in this
change: it is easy to follow anyway. Up to you, I am fine either way.
I will use if ( valid ) in the next version.
Cheers,
--
Julien Grall
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