A Xen PVH dom0 on an AMD processor triple faults early in boot on
6.6.86. CPU detection appears to fail, as the faulting instruction is
vmcall in xen_hypercall_intel() and not vmmcall in xen_hypercall_amd().
Detection fails because __xen_hypercall_setfunc() returns the full
kernel mapped address of xen_hypercall_amd() or xen_hypercall_intel() -
e.g. 0xffffffff815b93f0. But this is compared against the rip-relative
xen_hypercall_amd(%rip), which when running from identity mapping, is
only 0x015b93f0.
Replace the rip-relative address with just loading the actual address to
restore the proper comparision.
This only seems to affect PVH dom0 boot. This is probably because the
XENMEM_memory_map hypercall is issued early on from the identity
mappings. With a domU, the memory map is provided via hvm_start_info
and the hypercall is skipped. The domU is probably running from the
kernel high mapping when it issues hypercalls.
Signed-off-by: Jason Andryuk <jason.andr...@amd.com>
---
I think this sort of address mismatch would be addresed by
e8fbc0d9cab6 ("x86/pvh: Call C code via the kernel virtual mapping")
That could be backported instead, but it depends on a fair number of
patches.
Not sure on how getting a patch just into 6.6 would work. This patch
could go into upstream Linux though it's not strictly necessary when the
rip-relative address is a high address.
---
arch/x86/xen/xen-head.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 059f343da76d..71a0eda2da60 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -117,7 +117,7 @@ SYM_FUNC_START(xen_hypercall_hvm)
pop %ebx
pop %eax
#else
- lea xen_hypercall_amd(%rip), %rcx
+ mov $xen_hypercall_amd, %rcx
cmp %rax, %rcx
#ifdef CONFIG_FRAME_POINTER
pop %rax /* Dummy pop. */
--
2.49.0
