From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37970) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WPoJh-0001HV-J5 for qemu-devel@nongnu.org; Tue, 18 Mar 2014 03:20:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WPoJa-0001Xe-AL for qemu-devel@nongnu.org; Tue, 18 Mar 2014 03:20:05 -0400 Received: from thoth.sbs.de ([192.35.17.2]:47894) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WPoJa-0001XB-0d for qemu-devel@nongnu.org; Tue, 18 Mar 2014 03:19:58 -0400 Message-ID: <5327F398.7040509@siemens.com> Date: Tue, 18 Mar 2014 08:19:52 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <20140317215455.2f14b61f@redhat.com> In-Reply-To: <20140317215455.2f14b61f@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH for-2.0?] target-i386: fix gdb debugging with large memory guests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino , qemu-devel Cc: peter.maydell@linaro.org, afaerber@suse.de On 2014-03-18 02:54, Luiz Capitulino wrote: > If you start a Linux guest with more than 4GB of memory and try to look at a > memory address, you will get an error from gdb: > > (gdb) p node_data[0]->node_id > Cannot access memory at address 0xffff88013fffd3a0 > (gdb) I suppose this is x86-64, not 32-bit with PTE, right? > > I debugged this down to x86_cpu_get_phys_page_debug(), it doesn't handle the > case where the PDPTE has the PS bit set (although I didn't check where Linux > sets that bit). This commit adds the PS bit handling, which fixes the problem > for me. > > Signed-off-by: Luiz capitulino > --- > > Two observations: > > 1. This bug has always existed, so it's not a regression, so I'm not sure > it's worth it to fix for 2.0 > > 2. I'm not familiar with every detail of x86_cpu_get_phys_page_debug(), > so I'm not completely sure this is the right thing to do > > target-i386/helper.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/target-i386/helper.c b/target-i386/helper.c > index 4f447b8..9b7803f 100644 > --- a/target-i386/helper.c > +++ b/target-i386/helper.c > @@ -951,6 +951,13 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr) > return -1; > } > > + if (pdpe & PG_PSE_MASK) { > + page_size = 1024 * 1024 * 1024; > + pte = pdpe & ~( (page_size - 1) & ~0xfff); > + pte &= ~(PG_NX_MASK | PG_HI_USER_MASK); > + goto out; > + } Does this also apply if we are not in long mode? I'll check this more carefully later. Jan > + > pde_addr = ((pdpe & ~0xfff & ~(PG_NX_MASK | PG_HI_USER_MASK)) + > (((addr >> 21) & 0x1ff) << 3)) & env->a20_mask; > pde = ldq_phys(cs->as, pde_addr); > @@ -993,6 +1000,7 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr) > pte = pte & env->a20_mask; > } > > +out: > page_offset = (addr & TARGET_PAGE_MASK) & (page_size - 1); > paddr = (pte & TARGET_PAGE_MASK) + page_offset; > return paddr; > -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux