Messages in this thread Patch in this message | | | Date | Wed, 26 May 2010 16:48:19 +0800 | From | Lai Jiangshan <> | Subject | [RESEND PATCH 1/3] kvm: calculate correct gfn for small host pages which emulates large guest pages |
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In Document/kvm/mmu.txt: gfn: Either the guest page table containing the translations shadowed by this page, or the base page frame for linear translations. See role.direct.
But in function FNAME(fetch)(), sp->gfn is incorrect when one of following situations occurred: 1) guest is 32bit paging and the guest PDE maps a 4-MByte page (backed by 4k host pages), FNAME(fetch)() miss handling the quadrant.
And if guest use pse-36, "table_gfn = gpte_to_gfn(gw->ptes[level - delta]);" is incorrect. 2) guest is long mode paging and the guest PDPTE maps a 1-GByte page (backed by 4k or 2M host pages).
So we fix it to suit to the document and suit to the code which requires sp->gfn correct when sp->role.direct=1.
We use the goal mapping gfn(gw->gfn) to calculate the base page frame for linear translations, it is simple and easy to be understood.
Reported-by: Marcelo Tosatti <mtosatti@redhat.com> Reported-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> --- diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 702c016..958e9c6 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -338,10 +338,13 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, direct = 1; if (!is_dirty_gpte(gw->ptes[level - delta])) access &= ~ACC_WRITE_MASK; - table_gfn = gpte_to_gfn(gw->ptes[level - delta]); - /* advance table_gfn when emulating 1gb pages with 4k */ - if (delta == 0) - table_gfn += PT_INDEX(addr, level); + /* + * It is a large guest pages backed by small host pages, + * So we set @direct(@shadow_page->role.direct)=1, and + * set @table_gfn(@shadow_page->gfn)=the base page frame + * for linear translations. + */ + table_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1); } else { direct = 0; table_gfn = gw->table_gfn[level - 2];
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