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Re: [PATCH 3/3] target/ppc: Check page dir/table base alignment

From: Richard Henderson
Subject: Re: [PATCH 3/3] target/ppc: Check page dir/table base alignment
Date: Thu, 23 Jun 2022 14:34:51 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1

On 6/23/22 07:26, Leandro Lupori wrote:
On 6/21/22 18:26, Fabiano Rosas wrote:
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Leandro Lupori <leandro.lupori@eldorado.org.br> writes:

Check if each page dir/table base address is properly aligned and
log a guest error if not, as real hardware behave incorrectly in
this case.

These checks are only performed when DEBUG_MMU is defined, to avoid
hurting the performance.

Signed-off-by: Leandro Lupori <leandro.lupori@eldorado.org.br>
  target/ppc/mmu-radix64.c | 21 +++++++++++++++++++++
  1 file changed, 21 insertions(+)

diff --git a/target/ppc/mmu-radix64.c b/target/ppc/mmu-radix64.c
index 2f0bcbfe2e..80d945a7c3 100644
--- a/target/ppc/mmu-radix64.c
+++ b/target/ppc/mmu-radix64.c
@@ -28,6 +28,8 @@
  #include "mmu-radix64.h"
  #include "mmu-book3s-v3.h"

+/* #define DEBUG_MMU */
  static bool ppc_radix64_get_fully_qualified_addr(const CPUPPCState *env,
                                                   vaddr eaddr,
                                                   uint64_t *lpid, uint64_t 
@@ -277,6 +279,16 @@ static int ppc_radix64_next_level(AddressSpace *as, vaddr 
      if (!(pde & R_PTE_LEAF)) { /* Prepare for next iteration */
          *nls = pde & R_PDE_NLS;
+#ifdef DEBUG_MMU
+        if ((pde & R_PDE_NLB) & MAKE_64BIT_MASK(0, *nls + 3)) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                "%s: misaligned page dir/table base: 0x%"VADDR_PRIx
+                " page dir size: 0x%"PRIx64" level: %d\n",
+                __func__, (pde & R_PDE_NLB), BIT(*nls + 3), *level);
+        }

Maybe use qemu_log_enabled() instead of the define? I think it is a
little more useful and has less chance to rot.

Ok. I wanted to avoid introducing any extra overhead, but I guess just checking qemu_log_enabled() should be ok.

No, qemu_log_enabled is *already* taken into account by qemu_log_mask.
Just drop the ifdefs.

Do you in fact need to raise an exception here?


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