[PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

[PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

[Thiago Jung Bauermann]

POWER secure guests (i.e., guests which use the Protection Execution
Facility) need to use SWIOTLB to be able to do I/O with the hypervisor, but
they don't need the SWIOTLB memory to be in low addresses since the
hypervisor doesn't have any addressing limitation.

This solves a SWIOTLB initialization problem we are seeing in secure guests
with 128 GB of RAM: they are configured with 4 GB of crashkernel reserved
memory, which leaves no space for SWIOTLB in low addresses.

To do this, we use mostly the same code as swiotlb_init(), but allocate the
buffer using memblock_alloc() instead of memblock_alloc_low().

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
 arch/powerpc/include/asm/svm.h       |  4 ++++
 arch/powerpc/mm/mem.c                |  6 +++++-
 arch/powerpc/platforms/pseries/svm.c | 26 ++++++++++++++++++++++++++
 3 files changed, 35 insertions(+), 1 deletion(-)

Changes from v2:
- Panic if unable to allocate buffer, as suggested by Christoph.

Changes from v1:
- Open-code swiotlb_init() in arch-specific code, as suggested by
  Christoph.

diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
index 85580b30aba4..7546402d796a 100644
--- a/arch/powerpc/include/asm/svm.h
+++ b/arch/powerpc/include/asm/svm.h
@@ -15,6 +15,8 @@ static inline bool is_secure_guest(void)
 	return mfmsr() & MSR_S;
 }
 
+void __init svm_swiotlb_init(void);
+
 void dtl_cache_ctor(void *addr);
 #define get_dtl_cache_ctor()	(is_secure_guest() ? dtl_cache_ctor : NULL)
 
@@ -25,6 +27,8 @@ static inline bool is_secure_guest(void)
 	return false;
 }
 
+static inline void svm_swiotlb_init(void) {}
+
 #define get_dtl_cache_ctor() NULL
 
 #endif /* CONFIG_PPC_SVM */
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index c2c11eb8dcfc..0f21bcb16405 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -50,6 +50,7 @@
 #include <asm/swiotlb.h>
 #include <asm/rtas.h>
 #include <asm/kasan.h>
+#include <asm/svm.h>
 
 #include <mm/mmu_decl.h>
 
@@ -290,7 +291,10 @@ void __init mem_init(void)
 	 * back to to-down.
 	 */
 	memblock_set_bottom_up(true);
-	swiotlb_init(0);
+	if (is_secure_guest())
+		svm_swiotlb_init();
+	else
+		swiotlb_init(0);
 #endif
 
 	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
diff --git a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c
index 40c0637203d5..81085eb8f225 100644
--- a/arch/powerpc/platforms/pseries/svm.c
+++ b/arch/powerpc/platforms/pseries/svm.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/mm.h>
+#include <linux/memblock.h>
 #include <asm/machdep.h>
 #include <asm/svm.h>
 #include <asm/swiotlb.h>
@@ -34,6 +35,31 @@ static int __init init_svm(void)
 }
 machine_early_initcall(pseries, init_svm);
 
+/*
+ * Initialize SWIOTLB. Essentially the same as swiotlb_init(), except that it
+ * can allocate the buffer anywhere in memory. Since the hypervisor doesn't have
+ * any addressing limitation, we don't need to allocate it in low addresses.
+ */
+void __init svm_swiotlb_init(void)
+{
+	unsigned char *vstart;
+	unsigned long bytes, io_tlb_nslabs;
+
+	io_tlb_nslabs = (swiotlb_size_or_default() >> IO_TLB_SHIFT);
+	io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
+
+	bytes = io_tlb_nslabs << IO_TLB_SHIFT;
+
+	vstart = memblock_alloc(PAGE_ALIGN(bytes), PAGE_SIZE);
+	if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, false))
+		return;
+
+	if (io_tlb_start)
+		memblock_free_early(io_tlb_start,
+				    PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
+	panic("SVM: Cannot allocate SWIOTLB buffer");
+}
+
 int set_memory_encrypted(unsigned long addr, int numpages)
 {
 	if (!PAGE_ALIGNED(addr))

Re: [PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

[Christoph Hellwig]

On Tue, Aug 18, 2020 at 07:11:26PM -0300, Thiago Jung Bauermann wrote:
> POWER secure guests (i.e., guests which use the Protection Execution
> Facility) need to use SWIOTLB to be able to do I/O with the hypervisor, but
> they don't need the SWIOTLB memory to be in low addresses since the
> hypervisor doesn't have any addressing limitation.
> 
> This solves a SWIOTLB initialization problem we are seeing in secure guests
> with 128 GB of RAM: they are configured with 4 GB of crashkernel reserved
> memory, which leaves no space for SWIOTLB in low addresses.
> 
> To do this, we use mostly the same code as swiotlb_init(), but allocate the
> buffer using memblock_alloc() instead of memblock_alloc_low().
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

Looks fine to me (except for the pointlessly long comment lines, but I've
been told that's the powerpc way).

Re: [PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

[Thiago Jung Bauermann]

Christoph Hellwig <hch@lst.de> writes:

> On Tue, Aug 18, 2020 at 07:11:26PM -0300, Thiago Jung Bauermann wrote:
>> POWER secure guests (i.e., guests which use the Protection Execution
>> Facility) need to use SWIOTLB to be able to do I/O with the hypervisor, but
>> they don't need the SWIOTLB memory to be in low addresses since the
>> hypervisor doesn't have any addressing limitation.
>> 
>> This solves a SWIOTLB initialization problem we are seeing in secure guests
>> with 128 GB of RAM: they are configured with 4 GB of crashkernel reserved
>> memory, which leaves no space for SWIOTLB in low addresses.
>> 
>> To do this, we use mostly the same code as swiotlb_init(), but allocate the
>> buffer using memblock_alloc() instead of memblock_alloc_low().
>> 
>> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
>
> Looks fine to me (except for the pointlessly long comment lines, but I've
> been told that's the powerpc way).

Thanks! Do I have your Reviewed-by?

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

Re: [PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

[Michael Ellerman]

Christoph Hellwig <hch@lst.de> writes:
> On Tue, Aug 18, 2020 at 07:11:26PM -0300, Thiago Jung Bauermann wrote:
>> POWER secure guests (i.e., guests which use the Protection Execution
>> Facility) need to use SWIOTLB to be able to do I/O with the hypervisor, but
>> they don't need the SWIOTLB memory to be in low addresses since the
>> hypervisor doesn't have any addressing limitation.
>> 
>> This solves a SWIOTLB initialization problem we are seeing in secure guests
>> with 128 GB of RAM: they are configured with 4 GB of crashkernel reserved
>> memory, which leaves no space for SWIOTLB in low addresses.
>> 
>> To do this, we use mostly the same code as swiotlb_init(), but allocate the
>> buffer using memblock_alloc() instead of memblock_alloc_low().
>> 
>> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
>
> Looks fine to me (except for the pointlessly long comment lines, but I've
> been told that's the powerpc way).

They're 80 columns AFAICS?

cheers

Re: [PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

[Konrad Rzeszutek Wilk]

On Tue, Aug 18, 2020 at 07:11:26PM -0300, Thiago Jung Bauermann wrote:
> POWER secure guests (i.e., guests which use the Protection Execution
> Facility) need to use SWIOTLB to be able to do I/O with the hypervisor, but
> they don't need the SWIOTLB memory to be in low addresses since the
> hypervisor doesn't have any addressing limitation.
> 
> This solves a SWIOTLB initialization problem we are seeing in secure guests
> with 128 GB of RAM: they are configured with 4 GB of crashkernel reserved
> memory, which leaves no space for SWIOTLB in low addresses.
> 
> To do this, we use mostly the same code as swiotlb_init(), but allocate the
> buffer using memblock_alloc() instead of memblock_alloc_low().
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>


> ---
>  arch/powerpc/include/asm/svm.h       |  4 ++++
>  arch/powerpc/mm/mem.c                |  6 +++++-
>  arch/powerpc/platforms/pseries/svm.c | 26 ++++++++++++++++++++++++++
>  3 files changed, 35 insertions(+), 1 deletion(-)
> 
> Changes from v2:
> - Panic if unable to allocate buffer, as suggested by Christoph.
> 
> Changes from v1:
> - Open-code swiotlb_init() in arch-specific code, as suggested by
>   Christoph.
> 
> diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
> index 85580b30aba4..7546402d796a 100644
> --- a/arch/powerpc/include/asm/svm.h
> +++ b/arch/powerpc/include/asm/svm.h
> @@ -15,6 +15,8 @@ static inline bool is_secure_guest(void)
>  	return mfmsr() & MSR_S;
>  }
>  
> +void __init svm_swiotlb_init(void);
> +
>  void dtl_cache_ctor(void *addr);
>  #define get_dtl_cache_ctor()	(is_secure_guest() ? dtl_cache_ctor : NULL)
>  
> @@ -25,6 +27,8 @@ static inline bool is_secure_guest(void)
>  	return false;
>  }
>  
> +static inline void svm_swiotlb_init(void) {}
> +
>  #define get_dtl_cache_ctor() NULL
>  
>  #endif /* CONFIG_PPC_SVM */
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index c2c11eb8dcfc..0f21bcb16405 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -50,6 +50,7 @@
>  #include <asm/swiotlb.h>
>  #include <asm/rtas.h>
>  #include <asm/kasan.h>
> +#include <asm/svm.h>
>  
>  #include <mm/mmu_decl.h>
>  
> @@ -290,7 +291,10 @@ void __init mem_init(void)
>  	 * back to to-down.
>  	 */
>  	memblock_set_bottom_up(true);
> -	swiotlb_init(0);
> +	if (is_secure_guest())
> +		svm_swiotlb_init();
> +	else
> +		swiotlb_init(0);
>  #endif
>  
>  	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
> diff --git a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c
> index 40c0637203d5..81085eb8f225 100644
> --- a/arch/powerpc/platforms/pseries/svm.c
> +++ b/arch/powerpc/platforms/pseries/svm.c
> @@ -7,6 +7,7 @@
>   */
>  
>  #include <linux/mm.h>
> +#include <linux/memblock.h>
>  #include <asm/machdep.h>
>  #include <asm/svm.h>
>  #include <asm/swiotlb.h>
> @@ -34,6 +35,31 @@ static int __init init_svm(void)
>  }
>  machine_early_initcall(pseries, init_svm);
>  
> +/*
> + * Initialize SWIOTLB. Essentially the same as swiotlb_init(), except that it
> + * can allocate the buffer anywhere in memory. Since the hypervisor doesn't have
> + * any addressing limitation, we don't need to allocate it in low addresses.
> + */
> +void __init svm_swiotlb_init(void)
> +{
> +	unsigned char *vstart;
> +	unsigned long bytes, io_tlb_nslabs;
> +
> +	io_tlb_nslabs = (swiotlb_size_or_default() >> IO_TLB_SHIFT);
> +	io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
> +
> +	bytes = io_tlb_nslabs << IO_TLB_SHIFT;
> +
> +	vstart = memblock_alloc(PAGE_ALIGN(bytes), PAGE_SIZE);
> +	if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, false))
> +		return;
> +
> +	if (io_tlb_start)
> +		memblock_free_early(io_tlb_start,
> +				    PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
> +	panic("SVM: Cannot allocate SWIOTLB buffer");
> +}
> +
>  int set_memory_encrypted(unsigned long addr, int numpages)
>  {
>  	if (!PAGE_ALIGNED(addr))

Re: [PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

[Thiago Jung Bauermann]

Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> writes:

> On Tue, Aug 18, 2020 at 07:11:26PM -0300, Thiago Jung Bauermann wrote:
>> POWER secure guests (i.e., guests which use the Protection Execution
>> Facility) need to use SWIOTLB to be able to do I/O with the hypervisor, but
>> they don't need the SWIOTLB memory to be in low addresses since the
>> hypervisor doesn't have any addressing limitation.
>> 
>> This solves a SWIOTLB initialization problem we are seeing in secure guests
>> with 128 GB of RAM: they are configured with 4 GB of crashkernel reserved
>> memory, which leaves no space for SWIOTLB in low addresses.
>> 
>> To do this, we use mostly the same code as swiotlb_init(), but allocate the
>> buffer using memblock_alloc() instead of memblock_alloc_low().
>> 
>> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Thanks!

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

Re: [PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

[Michael Ellerman]

On Tue, 18 Aug 2020 19:11:26 -0300, Thiago Jung Bauermann wrote:
> POWER secure guests (i.e., guests which use the Protection Execution
> Facility) need to use SWIOTLB to be able to do I/O with the hypervisor, but
> they don't need the SWIOTLB memory to be in low addresses since the
> hypervisor doesn't have any addressing limitation.
> 
> This solves a SWIOTLB initialization problem we are seeing in secure guests
> with 128 GB of RAM: they are configured with 4 GB of crashkernel reserved
> memory, which leaves no space for SWIOTLB in low addresses.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory
      https://git.kernel.org/powerpc/c/eae9eec476d13fad9af6da1f44a054ee02b7b161

cheers