Hi Oleksandr,
On 16/07/2022 16:29, Oleksandr Tyshchenko wrote:
On 16/07/2022 15:56, Oleksandr Tyshchenko wrote:
From: Oleksandr Tyshchenko <[email protected]>
Borrow the x86's check from p2m_remove_page() which was added
by the following commit: c65ea16dbcafbe4fe21693b18f8c2a3c5d14600e
"x86/p2m: don't assert that the passed in MFN matches for a remove"
and adjust it to the Arm code base.
Basically, this check will be strictly needed for the xenheap pages
after applying a subsequent commit which will introduce xenheap based
M2P approach on Arm. But, it will be a good opportunity to harden
the P2M code for *every* RAM pages since it is possible to remove
any GFN - MFN mapping currently on Arm (even with the wrong helpers).
Suggested-by: Julien Grall <[email protected]>
Signed-off-by: Oleksandr Tyshchenko <[email protected]>
---
You can find the corresponding discussion at:
https://urldefense.com/v3/__https://lore.kernel.org/xen-devel/[email protected]/__;!!GF_29dbcQIUBPA!3a2u-XL4NvAzSMfz72LARrdWVFvq2In5ZpUdxP2cSt7bM8PgV7P_ZclZG2R-rE9PcosUHyqsKRNfVG2TiM9Tlg$
[lore[.]kernel[.]org]
https://urldefense.com/v3/__https://lore.kernel.org/xen-devel/[email protected]/__;!!GF_29dbcQIUBPA!3a2u-XL4NvAzSMfz72LARrdWVFvq2In5ZpUdxP2cSt7bM8PgV7P_ZclZG2R-rE9PcosUHyqsKRNfVG0kg7IZSA$
[lore[.]kernel[.]org]
Changes V6 -> V7:
- make this commit to be the first
- update commit description and add a comment in code
---
xen/arch/arm/p2m.c | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index d00c2e462a..2a0d383df4 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -1308,11 +1308,39 @@ static inline int p2m_remove_mapping(struct
domain *d,
mfn_t mfn)
{
struct p2m_domain *p2m = p2m_get_hostp2m(d);
+ unsigned long i;
int rc;
p2m_write_lock(p2m);
+ /*
+ * Before removing the GFN - MFN mapping for any RAM pages make
sure
+ * that there is no difference between what is already mapped
and what
+ * is requested to be unmapped.
+ * If they don't match bail out early. For instance, this could
happen
+ * if two CPUs are requesting to unmap the same P2M concurrently.
Missing word: P2M *entry*
Yes. May I please ask, could this be done on the commit if this appears
to be the last version?
I have committed the series with the same typo.
Cheers,
--
Julien Grall
