Setting the stack to PAGE_SIZE - 1 sets the stack to being 1-byte aligned, which fails in usermode with alignment checks enabled (ie: with flags cr0.am set and eflags.ac set). This was causing an #AC in usermode.c when preparing to call the callback in run_in_user(). Aligning the stack fixes the issue. For the purposes of fixing the #AC in usermode.c the stack has to be aligned to at least an 8-byte boundary. Setting it to a page aligned boundary ensures any stack alignment requirements are met as x86_64 stacks generally want to be 16-byte aligned. Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx> --- x86/vmx.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/x86/vmx.c b/x86/vmx.c index 6dc9a55..44f4861 100644 --- a/x86/vmx.c +++ b/x86/vmx.c @@ -1242,7 +1242,7 @@ static void init_vmcs_guest(void) vmcs_write(GUEST_CR4, guest_cr4); vmcs_write(GUEST_SYSENTER_CS, KERNEL_CS); vmcs_write(GUEST_SYSENTER_ESP, - (u64)(guest_syscall_stack + PAGE_SIZE - 1)); + (u64)(guest_syscall_stack + PAGE_SIZE)); vmcs_write(GUEST_SYSENTER_EIP, (u64)(&entry_sysenter)); vmcs_write(GUEST_DR7, 0); vmcs_write(GUEST_EFER, rdmsr(MSR_EFER)); @@ -1292,7 +1292,7 @@ static void init_vmcs_guest(void) /* 26.3.1.4 */ vmcs_write(GUEST_RIP, (u64)(&guest_entry)); - vmcs_write(GUEST_RSP, (u64)(guest_stack + PAGE_SIZE - 1)); + vmcs_write(GUEST_RSP, (u64)(guest_stack + PAGE_SIZE)); vmcs_write(GUEST_RFLAGS, X86_EFLAGS_FIXED); /* 26.3.1.5 */ -- 2.34.1.173.g76aa8bc2d0-goog
