[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen stable-4.7] x86/mm: Always set _PAGE_ACCESSED on L4e updates
commit 9b76908e6e074d7efbeafe6bad066ecc5f3c3c43 Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> AuthorDate: Wed Jan 17 17:23:37 2018 +0100 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Wed Jan 17 17:23:37 2018 +0100 x86/mm: Always set _PAGE_ACCESSED on L4e updates Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> master commit: bd61fe94bee0556bc2f64999a4a8315b93f90f21 master date: 2018-01-15 13:53:16 +0000 --- xen/arch/x86/mm.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index ada12c0..50f500c 100644 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -1296,11 +1296,23 @@ get_page_from_l4e( _PAGE_USER|_PAGE_RW); \ } while ( 0 ) +/* + * When shadowing an L4 behind the guests back (e.g. for per-pcpu + * purposes), we cannot efficiently sync access bit updates from hardware + * (on the shadow tables) back into the guest view. + * + * We therefore unconditionally set _PAGE_ACCESSED even in the guests + * view. This will appear to the guest as a CPU which proactively pulls + * all valid L4e's into its TLB, which is compatible with the x86 ABI. + * + * At the time of writing, all PV guests set the access bit anyway, so + * this is no actual change in their behaviour. + */ #define adjust_guest_l4e(pl4e, d) \ do { \ if ( likely(l4e_get_flags((pl4e)) & _PAGE_PRESENT) && \ likely(!is_pv_32bit_domain(d)) ) \ - l4e_add_flags((pl4e), _PAGE_USER); \ + l4e_add_flags((pl4e), _PAGE_USER | _PAGE_ACCESSED); \ } while ( 0 ) #define unadjust_guest_l3e(pl3e, d) \ -- generated by git-patchbot for /home/xen/git/xen.git#stable-4.7 _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/xen-changelog
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