From: Lai Jiangshan Subject: [RESEND PATCH 1/3] kvm: calculate correct gfn for small host pages which emulates large guest pages Date: Wed, 26 May 2010 16:48:19 +0800 Message-ID: <4BFCE053.6040505@cn.fujitsu.com> References: <4BD97AC1.8070704@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , kvm@vger.kernel.org To: Lai Jiangshan , Avi Kivity Return-path: In-Reply-To: <4BD97AC1.8070704@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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 Reported-by: Gui Jianfeng Signed-off-by: Lai Jiangshan --- 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];