[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH] target/ppc: fix Hash64 MMU update of PTE bit R

From: Daniel Henrique Barboza
Subject: Re: [PATCH] target/ppc: fix Hash64 MMU update of PTE bit R
Date: Wed, 24 Nov 2021 10:40:17 -0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0

On 11/24/21 09:00, Leandro Lupori wrote:
When updating the R bit of a PTE, the Hash64 MMU was using a wrong byte
offset, causing the first byte of the adjacent PTE to be corrupted.
This caused a panic when booting FreeBSD, using the Hash MMU.

If you add a "Fixes:" tag with the commit that introduced the code you're
fixing, we can push it right away as a bug fix in 6.2 (assuming it doesn't
break anything else, of course).

The commit to be fixed in the case seems to be a2dd4e83e76b ("ppc/hash64:
Rework R and C bit updates")

One more comment below:

Signed-off-by: Leandro Lupori <leandro.lupori@eldorado.org.br>
  target/ppc/mmu-hash64.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
index 19832c4b46..f165ac691a 100644
--- a/target/ppc/mmu-hash64.c
+++ b/target/ppc/mmu-hash64.c
@@ -786,7 +786,7 @@ static void ppc_hash64_set_dsi(CPUState *cs, int mmu_idx, 
uint64_t dar, uint64_t
static void ppc_hash64_set_r(PowerPCCPU *cpu, hwaddr ptex, uint64_t pte1)
-    hwaddr base, offset = ptex * HASH_PTE_SIZE_64 + 16;
+    hwaddr base, offset = ptex * HASH_PTE_SIZE_64 + 14;

Instead of adding a '14' you should add a new #define in mmu-hash64.h with this
value, something like "HPTE64_R_R_SHIFT". This will avoid hardcoding literals
around the code and forcing us to go to the ISA every time we wonder what's
an apparently random number represents. There's also a "HPTE64_R_R" defined
there but I'm not sure if it's usable here, so feel free to create a new
macro if needed.

In that note, the original commit that added this code also added a lot of
hardcoded "15" values for the C bit update in spapr_hpte_set_c() and
ppc_hash64_set_c(), and a "14" value like you're changing here in 
If you're feeling generous I believe that another patch replacing these 
hardcoded values
with bit shift macros is warranted as well.



if (cpu->vhyp) {
          PPCVirtualHypervisorClass *vhc =

reply via email to

[Prev in Thread] Current Thread [Next in Thread]