Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761951AbYAKR3R (ORCPT ); Fri, 11 Jan 2008 12:29:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760683AbYAKR3J (ORCPT ); Fri, 11 Jan 2008 12:29:09 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:27951 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760263AbYAKR3H (ORCPT ); Fri, 11 Jan 2008 12:29:07 -0500 X-SBRS: None X-MesageID: 37345073 X-Ironport-Server: ftlpip02.citrite.net X-Remote-IP: 216.142.71.134 X-Policy: $Relay X-IronPort-AV: E=Sophos;i="4.24,272,1196658000"; d="scan'208";a="37345073" Message-ID: <4787A72E.8060704@citrix.com> Date: Fri, 11 Jan 2008 09:28:14 -0800 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Jan Beulich CC: Jeremy Fitzhardinge , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH] adjust/fix LDT handling for Xen References: <4787436E.76E4.0078.0@novell.com> In-Reply-To: <4787436E.76E4.0078.0@novell.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4695 Lines: 143 Jan Beulich wrote: > Don't rely on kmalloc(PAGE_SIZE) returning PAGE_SIZE aligned memory > (Xen requires GDT *and* LDT to be page-aligned). Can kmalloc return non-page-aligned PAGE_SIZE allocations? > Using the page > allocator interface also removes the (albeit small) slab allocator > overhead. Runtime or space overhead? Given that they're once-off allocations, the time part isn't a big factor. And apparently LDT is completely unused. Seems like a reasonable change either way. > The same change being done for 64-bits for consistency. > > Further, the Xen hypercall interface expects the LDT address to be > virtual, not machine. > Shows how much the LDT gets used then... Hm, but I didn't make that code up; I wonder where it came from? But certainly, passing the mfn of the first page of a vmalloc area doesn't make any sense. > Signed-off-by: Jan Beulich > Cc: Ingo Molnar > Acked-by: Jeremy Fitzhardinge > --- > arch/x86/kernel/ldt_32.c | 7 +++---- > arch/x86/kernel/ldt_64.c | 7 +++---- > arch/x86/xen/enlighten.c | 9 +-------- > 3 files changed, 7 insertions(+), 16 deletions(-) > > --- linux-2.6.24-rc7/arch/x86/kernel/ldt_32.c 2008-01-10 16:53:54.000000000 +0100 > +++ 2.6.24-rc7-x86-xen-ldt/arch/x86/kernel/ldt_32.c 2008-01-09 13:59:50.000000000 +0100 > @@ -9,7 +9,6 @@ > #include > #include > #include > -#include > > #include > #include > @@ -38,7 +37,7 @@ static int alloc_ldt(mm_context_t *pc, i > if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE) > newldt = vmalloc(mincount*LDT_ENTRY_SIZE); > else > - newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL); > + newldt = (void *)__get_free_page(GFP_KERNEL); > > if (!newldt) > return -ENOMEM; > @@ -69,7 +68,7 @@ static int alloc_ldt(mm_context_t *pc, i > if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE) > vfree(oldldt); > else > - kfree(oldldt); > + put_page(virt_to_page(oldldt)); > } > return 0; > } > @@ -114,7 +113,7 @@ void destroy_context(struct mm_struct *m > if (mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE) > vfree(mm->context.ldt); > else > - kfree(mm->context.ldt); > + put_page(virt_to_page(mm->context.ldt)); > mm->context.size = 0; > } > } > --- linux-2.6.24-rc7/arch/x86/kernel/ldt_64.c 2008-01-10 16:53:54.000000000 +0100 > +++ 2.6.24-rc7-x86-xen-ldt/arch/x86/kernel/ldt_64.c 2008-01-09 13:59:50.000000000 +0100 > @@ -12,7 +12,6 @@ > #include > #include > #include > -#include > > #include > #include > @@ -41,7 +40,7 @@ static int alloc_ldt(mm_context_t *pc, u > if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE) > newldt = vmalloc(mincount*LDT_ENTRY_SIZE); > else > - newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL); > + newldt = (void *)__get_free_page(GFP_KERNEL); > > if (!newldt) > return -ENOMEM; > @@ -73,7 +72,7 @@ static int alloc_ldt(mm_context_t *pc, u > if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE) > vfree(oldldt); > else > - kfree(oldldt); > + put_page(virt_to_page(oldldt)); > } > return 0; > } > @@ -117,7 +116,7 @@ void destroy_context(struct mm_struct *m > if ((unsigned)mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE) > vfree(mm->context.ldt); > else > - kfree(mm->context.ldt); > + put_page(virt_to_page(mm->context.ldt)); > mm->context.size = 0; > } > } > --- linux-2.6.24-rc7/arch/x86/xen/enlighten.c 2008-01-10 16:53:55.000000000 +0100 > +++ 2.6.24-rc7-x86-xen-ldt/arch/x86/xen/enlighten.c 2008-01-09 14:00:51.000000000 +0100 > @@ -275,19 +275,12 @@ static unsigned long xen_store_tr(void) > > static void xen_set_ldt(const void *addr, unsigned entries) > { > - unsigned long linear_addr = (unsigned long)addr; > struct mmuext_op *op; > struct multicall_space mcs = xen_mc_entry(sizeof(*op)); > > op = mcs.args; > op->cmd = MMUEXT_SET_LDT; > - if (linear_addr) { > - /* ldt my be vmalloced, use arbitrary_virt_to_machine */ > - xmaddr_t maddr; > - maddr = arbitrary_virt_to_machine((unsigned long)addr); > - linear_addr = (unsigned long)maddr.maddr; > - } > - op->arg1.linear_addr = linear_addr; > + op->arg1.linear_addr = (unsigned long)addr; > op->arg2.nr_ents = entries; > > MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF); > > > > -- 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/