From: Andres Lagar-Cavilla Date: Tue, 6 Dec 2011 20:31:49 +0000 (+0000) Subject: Improve handling of nested page faults X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks://%22Dat/%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22Dat?a=commitdiff_plain;h=5cd6d1bc78ed69f543ef608adf577d3b76983cb8;p=xen.git Improve handling of nested page faults Add checks for access type. Be less reliant on implicit semantics. Signed-off-by: Andres Lagar-Cavilla Acked-by: Tim Deegan Committed-by: Tim Deegan --- diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c index 92f647bfa3..210e65abf3 100644 --- a/xen/arch/x86/hvm/hvm.c +++ b/xen/arch/x86/hvm/hvm.c @@ -1288,7 +1288,8 @@ int hvm_hap_nested_page_fault(unsigned long gpa, * If this GFN is emulated MMIO or marked as read-only, pass the fault * to the mmio handler. */ - if ( (p2mt == p2m_mmio_dm) || (p2mt == p2m_ram_ro) ) + if ( (p2mt == p2m_mmio_dm) || + (access_w && (p2mt == p2m_ram_ro)) ) { if ( !handle_mmio() ) hvm_inject_exception(TRAP_gp_fault, 0, 0); @@ -1302,7 +1303,7 @@ int hvm_hap_nested_page_fault(unsigned long gpa, p2m_mem_paging_populate(v->domain, gfn); /* Mem sharing: unshare the page and try again */ - if ( p2mt == p2m_ram_shared ) + if ( access_w && (p2mt == p2m_ram_shared) ) { ASSERT(!p2m_is_nestedp2m(p2m)); mem_sharing_unshare_page(p2m->domain, gfn, 0); @@ -1319,14 +1320,17 @@ int hvm_hap_nested_page_fault(unsigned long gpa, * a large page, we do not change other pages type within that large * page. */ - paging_mark_dirty(v->domain, mfn_x(mfn)); - p2m_change_type(v->domain, gfn, p2m_ram_logdirty, p2m_ram_rw); + if ( access_w ) + { + paging_mark_dirty(v->domain, mfn_x(mfn)); + p2m_change_type(v->domain, gfn, p2m_ram_logdirty, p2m_ram_rw); + } rc = 1; goto out_put_gfn; } /* Shouldn't happen: Maybe the guest was writing to a r/o grant mapping? */ - if ( p2mt == p2m_grant_map_ro ) + if ( access_w && (p2mt == p2m_grant_map_ro) ) { gdprintk(XENLOG_WARNING, "trying to write to read-only grant mapping\n");