From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH v4 08/11] xen/arm: Handle remove foreign mapping Date: Mon, 16 Dec 2013 16:40:52 +0000 Message-ID: <52AF2D14.3060500@linaro.org> References: <1386963461-6520-1-git-send-email-julien.grall@linaro.org> <1386963461-6520-9-git-send-email-julien.grall@linaro.org> <20131216115131.GB35881@deinos.phlegethon.org> <52AF1D6E.7080402@linaro.org> <1387208403.21086.12.camel@kazak.uk.xensource.com> <52AF29C3.1030700@linaro.org> <1387211584.21086.27.camel@kazak.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1VsbE0-0006Vs-IL for xen-devel@lists.xenproject.org; Mon, 16 Dec 2013 16:40:56 +0000 Received: by mail-wi0-f175.google.com with SMTP id hi5so2412488wib.8 for ; Mon, 16 Dec 2013 08:40:54 -0800 (PST) In-Reply-To: <1387211584.21086.27.camel@kazak.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: Keir Fraser , patches@linaro.org, Tim Deegan , stefano.stabellini@citrix.com, Jan Beulich , xen-devel@lists.xenproject.org List-Id: xen-devel@lists.xenproject.org On 12/16/2013 04:33 PM, Ian Campbell wrote: > On Mon, 2013-12-16 at 16:26 +0000, Julien Grall wrote: >> >> On 12/16/2013 03:40 PM, Ian Campbell wrote: >>> On Mon, 2013-12-16 at 15:34 +0000, Julien Grall wrote: >>>> >>>> On 12/16/2013 11:51 AM, Tim Deegan wrote: >>>>> At 19:37 +0000 on 13 Dec (1386959858), Julien Grall wrote: >>>>>> @@ -693,12 +694,21 @@ long do_memory_op(unsigned long cmd, XEN_GUEST_HANDLE_PARAM(void) arg) >>>>>> return rc; >>>>>> } >>>>>> >>>>>> - page = get_page_from_gfn(d, xrfp.gpfn, NULL, P2M_ALLOC); >>>>>> + /* >>>>>> + * If autotranslate guest, (eg pvh), the gfn could be mapped to a mfn >>>>>> + * from foreign domain by the user space tool during domain creation. >>>>>> + * We need to check for that, free it up from the p2m, and release >>>>>> + * refcnt on it. In such a case, page would be NULL and the following >>>>>> + * call would not have refcnt'd the page. >>>>>> + */ >>>>>> + page = get_page_from_gfn(d, xrfp.gpfn, &p2mt, P2M_ALLOC); >>>>>> if ( page ) >>>>>> { >>>>>> guest_physmap_remove_page(d, xrfp.gpfn, page_to_mfn(page), 0); >>>>>> put_page(page); >>>>>> } >>>>>> + else if ( p2m_is_foreign(p2mt) ) >>>>>> + rc = p2m_remove_foreign(d, xrfp.gpfn); >>>>> >>>>> This doesn't seem like the right interface -- having special cases >>>>> like this in the callers is something we slipped into in x86 for a lot >>>>> of the paging/sharing code and it's not nice. I think maybe we can >>>>> just have get_page_from_gfn() DTRT for foreign (and grant) entries. >>>>> >>>>> Also, the comment will have been out of data by the time the x86 >>>>> version of this code is finished, as we won't be handling the refcount >>>>> at this level. :) >>>> >>>> I will remove the comment and modify get_page_from_gfn to handle foreign >>>> mapping. >>> >>> You'll want to coordinate with Mukesh on that latter I think. >>> >>> Ian. >>> >>> >> >> I have reworked this patch. I get a simpler patch: >> >> commit aab2e5d2ae7d0fa87c74cae2f22044f87be33f70 >> Author: Julien Grall >> Date: Fri Dec 13 16:51:03 2013 +0000 >> >> xen/arm: Handle remove foreign mapping >> >> Modify get_page_from_gfn to take reference on foreign mapping. This will avoid >> specific handling in the common code. >> >> Signed-off-by: Julien Grall >> >> --- >> Changes in v5: >> - Remove specific p2m handling in common code >> - Handle foreign mapping in get_page_from_gfn >> Changes in v4: >> - Split patch #6 from dom0 pvh series v6.2 to retrieve only common >> code. >> - Rework commit title >> - Rename xen_rem_foreign_from_p2m in p2m_remove_foreign >> - Get the mfn from the pte. We are not sure that maddr given in >> parameters is valid >> Changes in v3: >> - Move put_page in create_p2m_entries >> - Move xenmem_rem_foreign_from_p2m in arch/arm/p2m.c >> Changes in v2: >> - Introduce the patch >> >> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c >> index 39d8a03..f7bd7e2 100644 >> --- a/xen/arch/arm/p2m.c >> +++ b/xen/arch/arm/p2m.c >> @@ -317,10 +317,21 @@ static int create_p2m_entries(struct domain *d, >> break; >> case REMOVE: >> { >> - lpae_t pte; >> + lpae_t pte = third[third_table_offset(addr)]; >> + unsigned long mfn; >> + >> + maddr = (pte.bits & PADDR_MASK & PAGE_MASK); > > I thought we had a macro for this, but apparently not. While looking for > it I spotted that x86 has pte_to_mfn, which sounds like a useful > innovation... (not essential as part of this series though). This function is only defined for mini-os (extras/mini-os/include/x86/arch_mm.h). > >> + mfn = paddr_to_pfn(maddr); >> + >> + /* TODO: Handle other p2m type */ >> + if ( pte.p2m.valid && p2m_is_foreign(pte.p2m.type) ) >> + { >> + ASSERT(mfn_valid(mfn)); > > Something somewhere is making sure we don't put foreign MMIO regions > into the p2m, right? We retrieve the mfn via page_to_mfn, so the mfn should be valid. > >> + put_page(mfn_to_page(mfn)); >> + } >> + >> memset(&pte, 0x00, sizeof(pte)); >> write_pte(&third[third_table_offset(addr)], pte); >> - maddr += PAGE_SIZE; >> } >> break; >> } >> diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h >> index 0eb07a8..e0b58da 100644 >> --- a/xen/include/asm-arm/p2m.h >> +++ b/xen/include/asm-arm/p2m.h >> @@ -122,9 +122,21 @@ static inline struct page_info *get_page_from_gfn( >> if ( !mfn_valid(mfn) ) >> return NULL; >> page = mfn_to_page(mfn); >> - if ( !get_page(page, d) ) >> - return NULL; >> - return page; >> + >> + if ( get_page(page, d) ) > > This isn't noisy (even at debug level) on failure, I thought so? > > Might be safer (and TBH more logical) to move it after the foreign > special case. Will do. > >> + return page; >> + >> + /* get_page won't work on foreign mapping because the page doesn't >> + * belong to the current domain. >> + */ >> + if ( p2mt == p2m_map_foreign ) >> + { >> + struct domain *fdom = page_get_owner_and_reference(page); >> + ASSERT(fdom != NULL); > > ASSERT(fdom != d) > ? Both are valid. We need to make sure that the page belongs to a domain, and then it's not the current domain. -- Julien Grall