From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chen, Tiejun" Subject: Re: [v7][RFC][PATCH 08/13] xen/x86/p2m: set p2m_access_n for reserved device memory mapping Date: Mon, 03 Nov 2014 17:51:15 +0800 Message-ID: <54575013.50702@intel.com> References: <1414136077-18599-1-git-send-email-tiejun.chen@intel.com> <1414136077-18599-9-git-send-email-tiejun.chen@intel.com> <544A88560200007800042056@mail.emea.novell.com> <544E0ACA.8050201@intel.com> <544E2D8002000078000425A9@mail.emea.novell.com> <544F531C.7060401@intel.com> <544F7A310200007800042BAC@mail.emea.novell.com> <5450A330.6020102@intel.com> <5450BF63020000780004305E@mail.emea.novell.com> <5451EB48.9010103@intel.com> <545211DA0200007800043645@mail.emea.novell.com> <5452F8D8.9050009@intel.com> <545355720200007800043D97@mail.emea.novell.com> <54571E91.4030903@intel.com> <5457523A02000078000443C7@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5457523A02000078000443C7@mail.emea.novell.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: Jan Beulich Cc: yang.z.zhang@intel.com, kevin.tian@intel.com, tim@xen.org, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 2014/11/3 17:00, Jan Beulich wrote: >>>> On 03.11.14 at 07:20, wrote: >> On 2014/10/31 16:25, Jan Beulich wrote: >>>>>> On 31.10.14 at 03:50, wrote: >>>> On 2014/10/30 17:24, Jan Beulich wrote: >>>>>>>> On 30.10.14 at 08:39, wrote: >>>>>> @@ -686,8 +686,22 @@ guest_physmap_add_entry(struct domain *d, unsigned long gfn, >>>>>> /* Now, actually do the two-way mapping */ >>>>>> if ( mfn_valid(_mfn(mfn)) ) >>>>>> { >>>>>> - rc = p2m_set_entry(p2m, gfn, _mfn(mfn), page_order, t, >>>>>> - p2m->default_access); >>>>>> + rc = 0; >>>>>> + a = p2m->default_access; >>>>>> + if ( !is_hardware_domain(d) ) >>>>>> + { >>>>>> + rc = iommu_get_reserved_device_memory(p2m_check_reserved_device_memory, >>>>>> + &gfn); >>>>>> + /* We need to set reserved device memory as p2m_access_n. */ >>>>>> + if ( rc == 1 ) >>>>>> + a = p2m_access_n; >>>>>> + else if ( rc < 0 ) >>>>>> + printk(XENLOG_WARNING >>>>>> + "Domain %d can't check reserved device memory.\n", >>>>>> + d->domain_id); >>>>>> + } >>>>>> + >>>>>> + rc = p2m_set_entry(p2m, gfn, _mfn(mfn), page_order, t, a); >>>>>> if ( rc ) >>>>>> goto out; /* Failed to update p2m, bail without updating m2p. >>>> */ >>>>> >>>>> The handling of "a" looks good now, but the error handling and >>>>> logging is still as broken as it was before. >>>> >>>> Do you mean I'm missing some necessary info? Like gfn and mfn, so domain >>>> id, gfn and mfn can show enough message. >>>> >>>> Sorry I'm poor to understand what you expect. >>> >>> But I explained it already, and that explanation is still visible in >>> the quotes above. But to avoid any doubt, I'll repeat: "And >> >> I tried to understand what you said but felt a confusion so ask if you >> show me directly. >> >>> properly handle the error case (just logging a message - which >>> btw lacks a proper XENLOG_G_* prefix - doesn't seem enough >>> to me)." >> >> Looks there are two problems: >> >> #1: the error message >> >> If current line is not fine, >> printk(XENLOG_G_WARNING "Domain %d can't check reserved device >> memory.\n", d->domain_id); >> >> I mean could you change this directly. > > This looks reasonable, albeit we generally prefer Dom%d or dom%d > so that messages are somewhat grep-able. Fixed. > >> #2 the error handling >> >> In an error case what should I do? Currently we still create these >> mapping as normal. This means these mfns will be valid so later we can't >> set them again then device can't be assigned as passthrough. I think >> this makes sense. Or we should just stop them from setting 1:1 mapping? > > You should, with very few exceptions, not ignore errors (which > includes "handling" them by just logging a message. Instead, you > should propagate the error back up the call chain. > Do you mean in your patch, +int iommu_get_reserved_device_memory(iommu_grdm_t *func, void *ctxt) +{ + const struct iommu_ops *ops = iommu_get_ops(); + + if ( !iommu_enabled || !ops->get_reserved_device_memory ) + return 0; + + return ops->get_reserved_device_memory(func, ctxt); +} + I shouldn't return that directly. Then instead, we should handle all error scenarios here? Thanks Tiejun