Subject: Re: [PATCH v5 4/7] powerpc/mm: Use UV_WRITE_PATE ucall to register a PATE

From: Michael Ellerman <[email-masked]>
Date: Wed, 14 Aug 2019 21:33:12 +1000

Hi Claudio,

Claudio Carvalho <[email-masked]> writes:
> From: Michael Anderson <[email-masked]>
>
> In ultravisor enabled systems, the ultravisor creates and maintains the
> partition table in secure memory where the hypervisor cannot access, and
                                   ^
                                   which?

> therefore, the hypervisor have to do the UV_WRITE_PATE ucall whenever it
                            ^          ^
                            has        a
> wants to set a partition table entry (PATE).
>
> This patch adds the UV_WRITE_PATE ucall and uses it to set a PATE if
> ultravisor is enabled. Additionally, this also also keeps a copy of the
> partition table because the nestMMU does not have access to secure
> memory. Such copy has entries for nonsecure and hypervisor partition.

I'm having trouble parsing the last sentence there.

Or at least it doesn't seem to match the code, or I don't understand
either the code or the comment. More below.

> diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
> index 85bc81abd286..033731f5dbaa 100644
> --- a/arch/powerpc/mm/book3s64/pgtable.c
> +++ b/arch/powerpc/mm/book3s64/pgtable.c
> @@ -213,34 +223,50 @@ void __init mmu_partition_table_init(void)
>  	powernv_set_nmmu_ptcr(ptcr);
>  }
>  
> -void mmu_partition_table_set_entry(unsigned int lpid, unsigned long dw0,
> -				   unsigned long dw1)
> +/*
> + * Global flush of TLBs and partition table caches for this lpid. The type of
> + * flush (hash or radix) depends on what the previous use of this partition ID
> + * was, not the new use.
> + */
> +static void flush_partition(unsigned int lpid, unsigned long old_patb0)

A nicer API would be for the 2nd param to be a "bool radix", and have
the caller worry about the fact that it comes from (patb0 & PATB_HR).

>  {
> -	unsigned long old = be64_to_cpu(partition_tb[lpid].patb0);
> -
> -	partition_tb[lpid].patb0 = cpu_to_be64(dw0);
> -	partition_tb[lpid].patb1 = cpu_to_be64(dw1);
> -
> -	/*
> -	 * Global flush of TLBs and partition table caches for this lpid.
> -	 * The type of flush (hash or radix) depends on what the previous
> -	 * use of this partition ID was, not the new use.
> -	 */
>  	asm volatile("ptesync" : : : "memory");
> -	if (old & PATB_HR) {
> -		asm volatile(PPC_TLBIE_5(%0,%1,2,0,1) : :
> +	if (old_patb0 & PATB_HR) {
> +		asm volatile(PPC_TLBIE_5(%0, %1, 2, 0, 1) : :
>  			     "r" (TLBIEL_INVAL_SET_LPID), "r" (lpid));
> -		asm volatile(PPC_TLBIE_5(%0,%1,2,1,1) : :
> +		asm volatile(PPC_TLBIE_5(%0, %1, 2, 1, 1) : :

That looks like an unrelated whitespace change.

>  			     "r" (TLBIEL_INVAL_SET_LPID), "r" (lpid));
>  		trace_tlbie(lpid, 0, TLBIEL_INVAL_SET_LPID, lpid, 2, 0, 1);
>  	} else {
> -		asm volatile(PPC_TLBIE_5(%0,%1,2,0,0) : :
> +		asm volatile(PPC_TLBIE_5(%0, %1, 2, 0, 0) : :

Ditto.

>  			     "r" (TLBIEL_INVAL_SET_LPID), "r" (lpid));
>  		trace_tlbie(lpid, 0, TLBIEL_INVAL_SET_LPID, lpid, 2, 0, 0);
>  	}
>  	/* do we need fixup here ?*/
>  	asm volatile("eieio; tlbsync; ptesync" : : : "memory");
>  }
> +
> +void mmu_partition_table_set_entry(unsigned int lpid, unsigned long dw0,
> +				  unsigned long dw1)
> +{
> +	unsigned long old = be64_to_cpu(partition_tb[lpid].patb0);
> +
> +	partition_tb[lpid].patb0 = cpu_to_be64(dw0);
> +	partition_tb[lpid].patb1 = cpu_to_be64(dw1);

ie. here we always update the copy of the partition table, regardless of
whether we're running under an ultravisor or not. So the copy is a
complete copy isn't it?

> +	/*
> +	 * In ultravisor enabled systems, the ultravisor maintains the partition
> +	 * table in secure memory where we don't have access, therefore, we have
> +	 * to do a ucall to set an entry.
> +	 */
> +	if (firmware_has_feature(FW_FEATURE_ULTRAVISOR)) {
> +		uv_register_pate(lpid, dw0, dw1);
> +		pr_info("PATE registered by ultravisor: dw0 = 0x%lx, dw1 = 0x%lx\n",
> +			dw0, dw1);
> +	} else {
> +		flush_partition(lpid, old);
> +	}

What is different is whether we flush or not.

And don't we still need to do the flush for the nestMMU? I assume we're
saying the ultravisor will broadcast a flush for us, which will also
handle the nestMMU case?

cheers