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Re: [Qemu-devel] [PATCH 2/2] ppc: Fix tlb invalidations on 6xx/7xx/7xxx
Re: [Qemu-devel] [PATCH 2/2] ppc: Fix tlb invalidations on 6xx/7xx/7xxx 32-bit processors
Tue, 7 Jun 2016 11:40:56 +1000
On Mon, Jun 06, 2016 at 07:52:48PM +1000, Benjamin Herrenschmidt wrote:
> The processor only uses some bits of the address and invalidates an
> entire congruence class. Some OSes such as Darwin and HelenOS take
> advantage of this and occasionally invalidate the entire TLB by just
> doing a series of 64 consecutive tlbie for example.
> Our code tries to be too smart here only invalidating a segment
> congruence class (ie, allowing more address bits to be relevant
> in the invalidation), this fails miserably on those OSes.
> Instead don't bother, do like ppc64 and blow the whole tlb when tlbie
> is executed.
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
Ugh, this patch too is showing as corrupt for me. I suspect the
problem is on my end, but I have no idea what, yet.
The concept looks good here, but I don't see much point to keeping the
old broken code around under the #if 0. I'll rewite accordingly and merge.
> target-ppc/mmu_helper.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
> diff --git a/target-ppc/mmu_helper.c b/target-ppc/mmu_helper.c
> index f5c4e69..a5e3878 100644
> --- a/target-ppc/mmu_helper.c
> +++ b/target-ppc/mmu_helper.c
> @@ -1969,6 +1969,11 @@ void ppc_tlb_invalidate_one(CPUPPCState *env,
> target_ulong addr)
> /* XXX: this case should be optimized,
> * giving a mask to tlb_flush_page
> + /* This is broken, some CPUs invalidate a whole congruence
> + * class on an even smaller subset of bits and some OSes take
> + * advantage of this. Just blow the whole thing away.
> + */
> +#if 0
> tlb_flush_page(cs, addr | (0x0 << 28));
> tlb_flush_page(cs, addr | (0x1 << 28));
> tlb_flush_page(cs, addr | (0x2 << 28));
> @@ -1985,6 +1990,9 @@ void ppc_tlb_invalidate_one(CPUPPCState *env,
> target_ulong addr)
> tlb_flush_page(cs, addr | (0xD << 28));
> tlb_flush_page(cs, addr | (0xE << 28));
> tlb_flush_page(cs, addr | (0xF << 28));
> + tlb_flush(cs, 1);
> #if defined(TARGET_PPC64)
> case POWERPC_MMU_64B:
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
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