| Message ID | 20240126145418.39520-1-roger.pau@citrix.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | x86/entry: fix jump into restore_all_guest without %rbx correctly set | expand |
On 26/01/2024 2:54 pm, Roger Pau Monne wrote: > e047b8d0fa05 went too far when limiting obtaining the vCPU pointer. While the > code in ist_dispatch_done does indeed only need the vCPU pointer when PV32 is > enabled, the !PV32 path will end up jumping into restore_all_guest which does > require rbx == vCPU pointer. > > Fix by moving the fetching of the vCPU pointer to be done outside of the PV32 > code block. > > Reported-by: Edwin Torok <edwin.torok@cloud.com> > Fixes: e047b8d0fa05 ('x86/entry: replace two GET_CURRENT() uses') > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> Thanks for getting to the bottom of this. This asm code is an unwieldy mess. We need to figure out a way to simplify it.
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S index 44f25def86bc..ecdd6e5b47a5 100644 --- a/xen/arch/x86/x86_64/entry.S +++ b/xen/arch/x86/x86_64/entry.S @@ -1139,8 +1139,9 @@ FUNC(handle_ist_exception) movl $EVENT_CHECK_VECTOR,%edi call send_IPI_self 1: -#ifdef CONFIG_PV32 + /* For restore_all_guest. */ mov STACK_CPUINFO_FIELD(current_vcpu)(%r14), %rbx +#ifdef CONFIG_PV32 movq VCPU_domain(%rbx),%rax cmpb $0,DOMAIN_is_32bit_pv(%rax) je restore_all_guest
e047b8d0fa05 went too far when limiting obtaining the vCPU pointer. While the code in ist_dispatch_done does indeed only need the vCPU pointer when PV32 is enabled, the !PV32 path will end up jumping into restore_all_guest which does require rbx == vCPU pointer. Fix by moving the fetching of the vCPU pointer to be done outside of the PV32 code block. Reported-by: Edwin Torok <edwin.torok@cloud.com> Fixes: e047b8d0fa05 ('x86/entry: replace two GET_CURRENT() uses') Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- xen/arch/x86/x86_64/entry.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)