From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55290) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gaNNp-00086P-Q0 for qemu-devel@nongnu.org; Fri, 21 Dec 2018 11:10:42 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gaNNl-0000J0-TD for qemu-devel@nongnu.org; Fri, 21 Dec 2018 11:10:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35510) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gaNNl-0000G4-Jw for qemu-devel@nongnu.org; Fri, 21 Dec 2018 11:10:37 -0500 Date: Fri, 21 Dec 2018 11:10:30 -0500 From: "Michael S. Tsirkin" Message-ID: <20181221110913-mutt-send-email-mst@kernel.org> References: <1544063533-10139-1-git-send-email-lizhijian@cn.fujitsu.com> <1544063533-10139-5-git-send-email-lizhijian@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1544063533-10139-5-git-send-email-lizhijian@cn.fujitsu.com> Subject: Re: [Qemu-devel] [PATCH for-4.0 v4 4/4] i386: allow to load initrd below 4G for recent linux List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Li Zhijian Cc: qemu-devel@nongnu.org, peter.maydell@linaro.org, philip.li@intel.com, zhijianx.li@intel.com, philmd@redhat.com, Paolo Bonzini , Richard Henderson , Eduardo Habkost , Marcel Apfelbaum On Thu, Dec 06, 2018 at 10:32:13AM +0800, Li Zhijian wrote: > a new field xloadflags was added to recent x86 linux, and BIT 1: > XLF_CAN_BE_LOADED_ABOVE_4G is used to tell bootload that where initrd can be > loaded safely. > > Current QEMU/BIOS always loads initrd below below_4g_mem_size which is always > less than 4G, so here limiting initrd_max to 4G - 1 simply is enough if > this bit is set. > > CC: Paolo Bonzini > CC: Richard Henderson > CC: Eduardo Habkost > CC: "Michael S. Tsirkin" > CC: Marcel Apfelbaum > Signed-off-by: Li Zhijian > > --- > V3: correct grammar and check XLF_CAN_BE_LOADED_ABOVE_4G first (Michael S. Tsirkin) > > Signed-off-by: Li Zhijian > --- > hw/i386/pc.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index 3b10726..baa99c0 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -904,7 +904,15 @@ static void load_linux(PCMachineState *pcms, > #endif > > /* highest address for loading the initrd */ > - if (protocol >= 0x203) { > + if (protocol >= 0x20c && > + lduw_p(header+0x236) & XLF_CAN_BE_LOADED_ABOVE_4G) { > + /* > + * Although kernel allows initrd loading to above 4G, > + * it just makes it as large as possible while still staying below 4G > + * since current BIOS always loads initrd below pcms->below_4g_mem_size > + */ > + initrd_max = UINT32_MAX; > + } else if (protocol >= 0x203) { > initrd_max = ldl_p(header+0x22c); > } else { > initrd_max = 0x37ffffff; I still have trouble understanding the above. Anyone else wants to comment / help rephrase the comment and commit log so it's readable? > -- > 2.7.4