Message ID | 20180404030301.25019-1-khandual@linux.vnet.ibm.com (mailing list archive) |
---|---|
State | RFC |
Headers | show |
Series | [RFC,1/2] powerpc/swiotlb: Dont free up allocated SWIOTLB slab on POWER | expand |
Anshuman Khandual <khandual@linux.vnet.ibm.com> writes: > Even though SWIOTLB slab gets allocated and initialized on powerpc with > swiotlb_init() called during mem_init(), it gets released away again on > POWER platform because 'ppc_swiotlb_enable' never gets set. The function > swiotlb_detect_4g() checks for 4GB memory and then sets the variable > 'ppc_swiotlb_enable' which prevents freeing up the SWIOTLB slab. Lets > make POWER platform call swiotlb_detect_4g() during setup_arch() which > will keep the SWIOTLB slab through out the runtime. > > A previous commit cf5621032f ("powerpc/64: Limit ZONE_DMA32 to 4GiB in > swiotlb_detect_4g()") enforced 4GB limit on ZONE_DMA32 which is is not > applicable on POWER (CONFIG_PPC_BOOK3S_64) platform. Lets remove this > unnecessary restriction. You're using "POWER" to mean Book3S 64-bit, but "POWER" is something else (the ISA for POWER1/POWER2). So please just say "Book3S 64-bit" or talk about a specific CPU, eg. Power9. > After the patch, SWIOTLB slab does not get released. > > [0.410992] software IO TLB [mem 0xfbff0000-0xffff0000] (64MB) mapped > at [00000000767f6cb3-000000004a10114f] But we don't want SWIOTLB on any existing Book3S 64-bit platforms, so leaving it enabled is just wasting memory. > diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c > index d73ec518ef80..c4db844e0b0d 100644 > --- a/arch/powerpc/kernel/setup-common.c > +++ b/arch/powerpc/kernel/setup-common.c > @@ -944,6 +944,7 @@ void __init setup_arch(char **cmdline_p) > /* Initialize the MMU context management stuff. */ > mmu_context_init(); > > + swiotlb_detect_4g(); You shouldn't be calling this, your use case has nothing to do with 4GB. Instead when you detect that you're running under the ultravisor then you should set ppc_swiotlb_enable = 1. cheers
On Wed, Apr 04, 2018 at 10:48:31PM +1000, Michael Ellerman wrote: > Anshuman Khandual <khandual@linux.vnet.ibm.com> writes: > > Even though SWIOTLB slab gets allocated and initialized on powerpc with > > swiotlb_init() called during mem_init(), it gets released away again on > > POWER platform because 'ppc_swiotlb_enable' never gets set. The function > > swiotlb_detect_4g() checks for 4GB memory and then sets the variable > > 'ppc_swiotlb_enable' which prevents freeing up the SWIOTLB slab. Lets > > make POWER platform call swiotlb_detect_4g() during setup_arch() which > > will keep the SWIOTLB slab through out the runtime. > > > > A previous commit cf5621032f ("powerpc/64: Limit ZONE_DMA32 to 4GiB in > > swiotlb_detect_4g()") enforced 4GB limit on ZONE_DMA32 which is is not > > applicable on POWER (CONFIG_PPC_BOOK3S_64) platform. Lets remove this > > unnecessary restriction. > > You're using "POWER" to mean Book3S 64-bit, but "POWER" is something > else (the ISA for POWER1/POWER2). > > So please just say "Book3S 64-bit" or talk about a specific CPU, eg. > Power9. > > > After the patch, SWIOTLB slab does not get released. > > > > [0.410992] software IO TLB [mem 0xfbff0000-0xffff0000] (64MB) mapped > > at [00000000767f6cb3-000000004a10114f] > > But we don't want SWIOTLB on any existing Book3S 64-bit platforms, so > leaving it enabled is just wasting memory. > > > diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c > > index d73ec518ef80..c4db844e0b0d 100644 > > --- a/arch/powerpc/kernel/setup-common.c > > +++ b/arch/powerpc/kernel/setup-common.c > > @@ -944,6 +944,7 @@ void __init setup_arch(char **cmdline_p) > > /* Initialize the MMU context management stuff. */ > > mmu_context_init(); > > > > + swiotlb_detect_4g(); > > You shouldn't be calling this, your use case has nothing to do with 4GB. > > Instead when you detect that you're running under the ultravisor then > you should set ppc_swiotlb_enable = 1. Please assume that you will have a interface to detect if you are running in a protected-environment(AKA secure-environment). So maybe you can rename swiotlb_detect_4g() to swiotlb_detect() and modify that function to enable or disable ppc_swiotlb_enable depending on the availability of 4g or availability of protected-environment? RP
diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma-swiotlb.c index 88f3963ca30f..2255c6dc89db 100644 --- a/arch/powerpc/kernel/dma-swiotlb.c +++ b/arch/powerpc/kernel/dma-swiotlb.c @@ -110,7 +110,7 @@ void __init swiotlb_detect_4g(void) { if ((memblock_end_of_DRAM() - 1) > 0xffffffff) { ppc_swiotlb_enable = 1; -#ifdef CONFIG_ZONE_DMA32 +#if defined(CONFIG_ZONE_DMA32) && !defined(CONFIG_PPC_BOOK3S_64) limit_zone_pfn(ZONE_DMA32, (1ULL << 32) >> PAGE_SHIFT); #endif } diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c index d73ec518ef80..c4db844e0b0d 100644 --- a/arch/powerpc/kernel/setup-common.c +++ b/arch/powerpc/kernel/setup-common.c @@ -944,6 +944,7 @@ void __init setup_arch(char **cmdline_p) /* Initialize the MMU context management stuff. */ mmu_context_init(); + swiotlb_detect_4g(); #ifdef CONFIG_PPC64 /* Interrupt code needs to be 64K-aligned. */ if ((unsigned long)_stext & 0xffff)
Even though SWIOTLB slab gets allocated and initialized on powerpc with swiotlb_init() called during mem_init(), it gets released away again on POWER platform because 'ppc_swiotlb_enable' never gets set. The function swiotlb_detect_4g() checks for 4GB memory and then sets the variable 'ppc_swiotlb_enable' which prevents freeing up the SWIOTLB slab. Lets make POWER platform call swiotlb_detect_4g() during setup_arch() which will keep the SWIOTLB slab through out the runtime. A previous commit cf5621032f ("powerpc/64: Limit ZONE_DMA32 to 4GiB in swiotlb_detect_4g()") enforced 4GB limit on ZONE_DMA32 which is is not applicable on POWER (CONFIG_PPC_BOOK3S_64) platform. Lets remove this unnecessary restriction. After the patch, SWIOTLB slab does not get released. [0.410992] software IO TLB [mem 0xfbff0000-0xffff0000] (64MB) mapped at [00000000767f6cb3-000000004a10114f] Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com> --- arch/powerpc/kernel/dma-swiotlb.c | 2 +- arch/powerpc/kernel/setup-common.c | 1 + 2 files changed, 2 insertions(+), 1 deletion(-)