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 <pbonz...@redhat.com> > CC: Richard Henderson <r...@twiddle.net> > CC: Eduardo Habkost <ehabk...@redhat.com> > CC: "Michael S. Tsirkin" <m...@redhat.com> > CC: Marcel Apfelbaum <marcel.apfelb...@gmail.com> > Signed-off-by: Li Zhijian <lizhij...@cn.fujitsu.com> > > --- > V3: correct grammar and check XLF_CAN_BE_LOADED_ABOVE_4G first (Michael S. > Tsirkin) > > Signed-off-by: Li Zhijian <lizhij...@cn.fujitsu.com> > --- > 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