On 16.07.22 18:06, Julien Grall wrote: > Hi Oleksandr,
Hello Julien > > In the future, please provide a cover letter (even if it is short) > when you bundle multiple patches. This is useful to make generic > comments and help threading in e-mail client (each patch would be a > subthread of 0 rather than 1). Yes, will do. > > 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? > > Other than that: > > Reviewed-by: Julien Grall <[email protected]> Thank you! > > > Cheers, > -- Regards, Oleksandr Tyshchenko
