From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34293) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gSkAg-000330-69 for qemu-devel@nongnu.org; Fri, 30 Nov 2018 09:53:35 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gSkAa-0007F1-Fv for qemu-devel@nongnu.org; Fri, 30 Nov 2018 09:53:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50794) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gSkAY-0007Dp-Hg for qemu-devel@nongnu.org; Fri, 30 Nov 2018 09:53:28 -0500 Date: Fri, 30 Nov 2018 09:53:23 -0500 From: "Michael S. Tsirkin" Message-ID: <20181130090249-mutt-send-email-mst@kernel.org> References: <1542765966-20244-1-git-send-email-lizhijian@cn.fujitsu.com> <1542765966-20244-2-git-send-email-lizhijian@cn.fujitsu.com> <1542765966-20244-3-git-send-email-lizhijian@cn.fujitsu.com> <1542765966-20244-4-git-send-email-lizhijian@cn.fujitsu.com> <1542765966-20244-5-git-send-email-lizhijian@cn.fujitsu.com> <1542765966-20244-6-git-send-email-lizhijian@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1542765966-20244-6-git-send-email-lizhijian@cn.fujitsu.com> Subject: Re: [Qemu-devel] [PATCH v2 5/5] x86: allow 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, Li Zhijian , Philip Li , Paolo Bonzini , Richard Henderson , Eduardo Habkost , Marcel Apfelbaum On Wed, Nov 21, 2018 at 10:06:06AM +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 saftly. safely > > Current QEMU always load loads > initrd below below_4g_mem_size which is > always > less than 4G, so here limit 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 > --- > hw/i386/pc.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index 2ffe6fb..6d4b973 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -92,6 +92,7 @@ > #define FW_CFG_HPET (FW_CFG_ARCH_LOCAL + 4) > > #define E820_NR_ENTRIES 16 > +#define XLF_CAN_BE_LOADED_ABOVE_4G_MASK (1 << 1) why not XLF_CAN_BE_LOADED_ABOVE_4G to be consistent with Linux? In fact let's import include/uapi/asm/bootparam.h into standard-headers, and use the macro from there? > > struct e820_entry { > uint64_t address; > @@ -916,6 +917,17 @@ static void load_linux(PCMachineState *pcms, > } else { > initrd_max = 0x37ffffff; > } > + if (protocol >= 0x20c) { Let's move it above so we have if (protocol >= 20c) else if 0x203 else > + unsigned int xloadflags = lduw_p(header+0x236); > + if (xloadflags & XLF_CAN_BE_LOADED_ABOVE_4G_MASK) { > + /* > + * Although kernel allow allows > initrd loading to above 4G, here we > + * limit initrd_max to 4G -1 Well not really, it just makes it as large as possible while still staying below 4G. > due to since > current QEMU always loads > + * initrd It's not QEMU, is it? It's actually the bios ... > below pcms->below_4g_mem_size > + */ > + initrd_max = UINT32_MAX; > + } > + } > > if (initrd_max >= pcms->below_4g_mem_size - pcmc->acpi_data_size) { > initrd_max = pcms->below_4g_mem_size - pcmc->acpi_data_size - 1; > -- > 2.7.4