[PATCH] target/i386: ensure EXCP0D_GPF is propagated back to the guest

[Mark Cave-Ayland]

In the case where mmu_translate() returns EXCP0D_GPF ensure that 
handle_mmu_fault()
returns immediately to propagate the fault back to the guest instead of 
returning
EXCP0E_PAGE.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Fixes: 661ff4879e ("target/i386: extract mmu_translate")
Closes: https://gitlab.com/qemu-project/qemu/-/issues/394
---

[Paolo: this appears to fix the regression booting Windows 7 on TCG that 
appeared in 6.1
 as per the above Gitlab issue. Unfortunately as I'm not really familiar with 
x86 it will
 probably need a better implementation/description but it should at least 
indicate what
 the problem is.]

 target/i386/tcg/sysemu/excp_helper.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/target/i386/tcg/sysemu/excp_helper.c 
b/target/i386/tcg/sysemu/excp_helper.c
index 7af887be4d..0170f7f791 100644
--- a/target/i386/tcg/sysemu/excp_helper.c
+++ b/target/i386/tcg/sysemu/excp_helper.c
@@ -439,6 +439,10 @@ static int handle_mmu_fault(CPUState *cs, vaddr addr, int 
size,
                                 prot, mmu_idx, page_size);
         return 0;
     } else {
+        if (cs->exception_index == EXCP0D_GPF) {
+            return 1;
+        }
+
         if (env->intercept_exceptions & (1 << EXCP0E_PAGE)) {
             /* cr2 is not modified in case of exceptions */
             x86_stq_phys(cs,
-- 
2.20.1