On 11/24/21 16:17, Leandro Lupori wrote:
On 11/24/21 14:40, Daniel Henrique Barboza wrote: > > > 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. I wonder how we never hit this issue before. Are you testing PowerNV and/or pSeries ? Could you share a FreeBDS image with us ? I've hit this issue while testing PowerNV. With pSeries it doesn't happen. It can be reproduced by trying to boot this iso: https://download.freebsd.org/ftp/snapshots/powerpc/powerpc64/ISO-IMAGES/14.0/FreeBSD-14.0-CURRENT-powerpc-powerpc64-20211028-4827bf76bce-250301-disc1.iso.xz It is easier to reproduce it using power8/powernv8. > 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") Indeed. Right. > One more comment below: > >> >> Signed-off-by: Leandro Lupori <leandro.lup...@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 spapr_hpte_set_r(). > If you're feeling generous I believe that another patch replacing these hardcoded values > with bit shift macros is warranted as well. What about creating HPTE64_R_R_BYTEand HPTE64_R_C_BYTE, with the values 14 and 15, respectively, to make it clear that these are byte offsets within a PTE?
Looks good to me. Daniel
May be for 7.0 though ? Thanks, C.