[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v12 5/6] x86/ioreq server: Asynchronously reset outstanding p2m_ioreq_server entries.
On 4/7/2017 5:40 PM, Jan Beulich wrote: On 06.04.17 at 17:53, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:--- a/xen/arch/x86/mm/p2m-ept.c +++ b/xen/arch/x86/mm/p2m-ept.c @@ -544,6 +544,12 @@ static int resolve_misconfig(struct p2m_domain *p2m, unsigned long gfn) e.ipat = ipat; if ( e.recalc && p2m_is_changeable(e.sa_p2mt) ) { + if ( e.sa_p2mt == p2m_ioreq_server ) + { + ASSERT(p2m->ioreq.entry_count > 0); + p2m->ioreq.entry_count--; + } + e.sa_p2mt = p2m_is_logdirty_range(p2m, gfn + i, gfn + i) ? p2m_ram_logdirty : p2m_ram_rw;I don't think this can be right: Why would it be valid to change the type from p2m_ioreq_server to p2m_ram_rw (or p2m_ram_logdirty) here, without taking into account further information? This code can run at any time, not just when you want to reset things. So at the very least there is a check missing whether a suitable ioreq server still exists (and only if it doesn't you want to do the type reset). Sorry, Jan. I think we have discussed this quite long ago.Indeed, there's information lacked here, and that's why global_logdirty is disallowed when there's remaining p2m_ioreq_server entries. :-) @@ -816,6 +822,22 @@ ept_set_entry(struct p2m_domain *p2m, unsigned long gfn, mfn_t mfn, new_entry.suppress_ve = is_epte_valid(&old_entry) ? old_entry.suppress_ve : 1;+ /*+ * p2m_ioreq_server is only used for 4K pages, so the + * count shall only happen on ept page table entries. + */ + if ( p2mt == p2m_ioreq_server ) + { + ASSERT(i == 0); + p2m->ioreq.entry_count++; + } + + if ( ept_entry->sa_p2mt == p2m_ioreq_server ) + { + ASSERT(p2m->ioreq.entry_count > 0 && i == 0);I think this would better be two ASSERT()s, so if one triggers it's clear what problem it was right away. The two conditions aren't really related to one another.@@ -965,7 +987,7 @@ static mfn_t ept_get_entry(struct p2m_domain *p2m, if ( is_epte_valid(ept_entry) ) { if ( (recalc || ept_entry->recalc) && - p2m_is_changeable(ept_entry->sa_p2mt) ) + p2m_check_changeable(ept_entry->sa_p2mt) )I think the distinction between these two is rather arbitrary, and I also think this is part of the problem above: Distinguishing log-dirty from ram-rw requires auxiliary data to be consulted. The same ought to apply to ioreq-server, and then there wouldn't be a need to have two p2m_*_changeable() flavors. Well, I think we have also discussed this quite long ago, here is the link. https://lists.xen.org/archives/html/xen-devel/2016-09/msg01017.html Of course the subsequent use p2m_is_logdirty_range() may then need amending. In the end it looks like you have the inverse problem here compared to above: You should return ram-rw when the reset was already initiated. At least that's how I would see the logic to match up with the log-dirty handling (where the _effective_ rather than the last stored type is being returned).@@ -606,6 +615,8 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long gfn, mfn_t mfn,if ( page_order == PAGE_ORDER_4K ){ + p2m_type_t p2mt_old; + rc = p2m_next_level(p2m, &table, &gfn_remainder, gfn, L2_PAGETABLE_SHIFT - PAGE_SHIFT, L2_PAGETABLE_ENTRIES, PGT_l1_page_table, 1); @@ -629,6 +640,21 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long gfn, mfn_t mfn, if ( entry_content.l1 != 0 ) p2m_add_iommu_flags(&entry_content, 0, iommu_pte_flags);+ p2mt_old = p2m_flags_to_type(l1e_get_flags(*p2m_entry));+ + /* + * p2m_ioreq_server is only used for 4K pages, so + * the count shall only be performed for level 1 entries. + */ + if ( p2mt == p2m_ioreq_server ) + p2m->ioreq.entry_count++; + + if ( p2mt_old == p2m_ioreq_server ) + { + ASSERT(p2m->ioreq.entry_count > 0); + p2m->ioreq.entry_count--; + } + /* level 1 entry */ p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 1);I think to match up with EPT you also want to add ASSERT(p2mt_old != p2m_ioreq_server); to the 2M and 1G paths. Is this really necessary? 2M and 1G page does not have p2mt_old, defining one and peek the p2m type just to have an ASSERT does not seem quite useful - and will hurt the performance. As to ept, since there's already a variable 'i', which may be greater than 0 - so I added an ASSERT. Yu Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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