Li, Xin B
2005-Jul-12 16:46 UTC
[Xen-devel] [PATCH] Fix debug exception stack to enable gdb on xeno64
Native x86_64 linux uses paranoidentry for exceptions with ist != 0, while x86_64 xenlinux doesn''t have special stacks for these exceptions. Actually we don''t need paranoidentry for x86_64 xenlinux, and these exceptions except #DB should be handled in hypervisor. With this patch, #DB is forwarded to guest, and let it use zeroentry should be OK. -Xin Signed-off-by: Xin Li <xin.b.li@intel.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Andi Kleen
2005-Jul-12 17:10 UTC
[Xen-devel] Re: [PATCH] Fix debug exception stack to enable gdb on xeno64
"Li, Xin B" <xin.b.li@intel.com> writes:> Native x86_64 linux uses paranoidentry for exceptions with ist != 0, > while x86_64 xenlinux doesn''t have special stacks for these exceptions. > Actually we don''t need paranoidentry for x86_64 xenlinux, and these > exceptions except #DB should be handled in hypervisor. With this patch, > #DB is forwarded to guest, and let it use zeroentry should be OK. > -XinDoesn''t look correct to me. When you get an NMI or DB directly after a SYSCALL to Xen it''ll execute on a random stack and likely break if the guest runs with a broken stack at that time. Also I can really recommend having IST stacks for double fault and stack fault, otherwise everytime you break the stack you get a triple fault which are nasty to debug. You guys with target probes might not care that much, but others do. -Andi _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2005-Jul-12 17:21 UTC
Re: [Xen-devel] Re: [PATCH] Fix debug exception stack to enable gdb on xeno64
On 12 Jul 2005, at 18:10, Andi Kleen wrote:> Doesn''t look correct to me. When you get an NMI or DB directly after > a SYSCALL to Xen it''ll execute on a random stack and likely break > if the guest runs with a broken stack at that time. > > Also I can really recommend having IST stacks for double fault and > stack > fault, otherwise everytime you break the stack you get a triple fault > which are nasty to debug. You guys with target probes might not > care that much, but others do.The patch is for guest Linux. Xen itself does use IST stacks, just like native Linux. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Andi Kleen
2005-Jul-12 17:37 UTC
Re: [Xen-devel] Re: [PATCH] Fix debug exception stack to enable gdb on xeno64
On Tue, Jul 12, 2005 at 06:21:59PM +0100, Keir Fraser wrote:> The patch is for guest Linux. Xen itself does use IST stacks, just like > native Linux.Same issue then, just from user space. -Andi _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel