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Mon, 25 Jan 2021 15:08:16 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 55A0BB939; Mon, 25 Jan 2021 15:08:15 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 8613deb2-f30f-4d8f-9d54-c9a098b3770f X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1611587295; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=o17tOZukL4o9r0k92R2c6OfOHdz1AEOOcFhqv2SY0zQ=; b=AEAuvxSqndagQ4roVbx3Bg5NoKKx539DS5ET6kLPbK6Imr0r8If+j+33O8agGDAhbylUfq LZ7B1IulVRPLTIKACIbI3tTufimKRcW/mFFZKQ8X1uzVXA5K8qSyWP+lqRbekG76paAY4y ujGeCLlD7S4cMu4UYujaPLqQyb5ImiU= Subject: Re: [PATCH v7 02/10] xen/domain: Add vmtrace_frames domain creation parameter To: Andrew Cooper Cc: =?UTF-8?Q?Micha=c5=82_Leszczy=c5=84ski?= , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Wei Liu , Anthony PERARD , Tamas K Lengyel , Xen-devel References: <20210121212718.2441-1-andrew.cooper3@citrix.com> <20210121212718.2441-3-andrew.cooper3@citrix.com> From: Jan Beulich Message-ID: <752e7de2-b95e-f7ab-0d14-877c72c66134@suse.com> Date: Mon, 25 Jan 2021 16:08:14 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210121212718.2441-3-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 21.01.2021 22:27, Andrew Cooper wrote: > --- a/xen/common/domain.c > +++ b/xen/common/domain.c > @@ -132,6 +132,48 @@ static void vcpu_info_reset(struct vcpu *v) > v->vcpu_info_mfn = INVALID_MFN; > } > > +static void vmtrace_free_buffer(struct vcpu *v) > +{ > + const struct domain *d = v->domain; > + struct page_info *pg = v->vmtrace.buf; > + unsigned int i; > + > + if ( !pg ) > + return; > + > + for ( i = 0; i < d->vmtrace_frames; i++ ) > + { > + put_page_alloc_ref(&pg[i]); > + put_page_and_type(&pg[i]); > + } > + > + v->vmtrace.buf = NULL; To set a good precedent, maybe this wants moving up ahead of the loop and ... > +} > + > +static int vmtrace_alloc_buffer(struct vcpu *v) > +{ > + struct domain *d = v->domain; > + struct page_info *pg; > + unsigned int i; > + > + if ( !d->vmtrace_frames ) > + return 0; > + > + pg = alloc_domheap_pages(d, get_order_from_pages(d->vmtrace_frames), > + MEMF_no_refcount); > + if ( !pg ) > + return -ENOMEM; > + > + v->vmtrace.buf = pg; ... this wants moving down past the loop, to avoid globally announcing something that isn't fully initialized yet / anymore? > + for ( i = 0; i < d->vmtrace_frames; i++ ) > + /* Domain can't know about this page yet - something fishy going on. */ > + if ( !get_page_and_type(&pg[i], d, PGT_writable_page) ) > + BUG(); Whatever the final verdict to the other similar places that one of your patch changes should be applied here, too. > --- a/xen/include/public/domctl.h > +++ b/xen/include/public/domctl.h > @@ -94,6 +94,7 @@ struct xen_domctl_createdomain { > uint32_t max_evtchn_port; > int32_t max_grant_frames; > int32_t max_maptrack_frames; > + uint32_t vmtrace_frames; Considering page size related irritations elsewhere in the public interface, could you have a comment clarify the unit of this value (Xen's page size according to the rest of the patch), and that space will be allocated once per-vCPU rather than per-domain (to stand a chance of recognizing the ultimate memory footprint resulting from this)? > --- a/xen/include/xen/sched.h > +++ b/xen/include/xen/sched.h > @@ -257,6 +257,10 @@ struct vcpu > /* vPCI per-vCPU area, used to store data for long running operations. */ > struct vpci_vcpu vpci; > > + struct { > + struct page_info *buf; > + } vmtrace; While perhaps minor, I'm unconvinced "buf" is a good name for a field of this type. > @@ -470,6 +474,9 @@ struct domain > unsigned pbuf_idx; > spinlock_t pbuf_lock; > > + /* Used by vmtrace features */ > + uint32_t vmtrace_frames; unsigned int? Also could you move this to an existing 32-bit hole, like immediately after "monitor"? Jan