Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757721Ab3IFQGf (ORCPT ); Fri, 6 Sep 2013 12:06:35 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:49897 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757433Ab3IFQGe (ORCPT ); Fri, 6 Sep 2013 12:06:34 -0400 Message-ID: <5229FD81.6000701@oracle.com> Date: Fri, 06 Sep 2013 12:06:25 -0400 From: konrad wilk Organization: Oracle Corporation User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Stefano Stabellini CC: Boris Ostrovsky , david.vrabel@citrix.com, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] xen/p2m: Don't call get_balloon_scratch_page() twice, keep interrupts disabled for multicalls References: <1378479646-12592-1-git-send-email-boris.ostrovsky@oracle.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2397 Lines: 66 On 9/6/2013 11:09 AM, Stefano Stabellini wrote: > On Fri, 6 Sep 2013, Boris Ostrovsky wrote: >> m2p_remove_override() calls get_balloon_scratch_page() in >> MULTI_update_va_mapping() even though it already has pointer to this page from >> the earlier call (in scratch_page). This second call doesn't have a matching >> put_balloon_scratch_page() thus not restoring preempt count back. (Also, there >> is no put_balloon_scratch_page() in the error path.) >> >> In addition, the second multicall uses __xen_mc_entry() which does not disable >> interrupts. Rearrange xen_mc_* calls to keep interrupts off while performing >> multicalls. >> >> Signed-off-by: Boris Ostrovsky You also might want to mention that this fixes the regression introduced by .. commit id <"title" > Reviewed-by: Stefano Stabellini > > >> arch/x86/xen/p2m.c | 10 ++++++---- >> 1 file changed, 6 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c >> index 0d4ec35..8b901e8 100644 >> --- a/arch/x86/xen/p2m.c >> +++ b/arch/x86/xen/p2m.c >> @@ -990,10 +990,13 @@ int m2p_remove_override(struct page *page, >> printk(KERN_WARNING "m2p_remove_override: " >> "pfn %lx mfn %lx, failed to modify kernel mappings", >> pfn, mfn); >> + put_balloon_scratch_page(); >> return -1; >> } >> >> - mcs = xen_mc_entry( >> + xen_mc_batch(); >> + >> + mcs = __xen_mc_entry( >> sizeof(struct gnttab_unmap_and_replace)); >> unmap_op = mcs.args; >> unmap_op->host_addr = kmap_op->host_addr; >> @@ -1003,12 +1006,11 @@ int m2p_remove_override(struct page *page, >> MULTI_grant_table_op(mcs.mc, >> GNTTABOP_unmap_and_replace, unmap_op, 1); >> >> - xen_mc_issue(PARAVIRT_LAZY_MMU); >> - >> mcs = __xen_mc_entry(0); >> MULTI_update_va_mapping(mcs.mc, scratch_page_address, >> - pfn_pte(page_to_pfn(get_balloon_scratch_page()), >> + pfn_pte(page_to_pfn(scratch_page), >> PAGE_KERNEL_RO), 0); >> + >> xen_mc_issue(PARAVIRT_LAZY_MMU); >> >> kmap_op->host_addr = 0; >> -- >> 1.8.3.1 >> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/