powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

POWER secure guests (i.e., guests which use the Protected 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().

Fixes: 2efbc58f157a ("powerpc/pseries/svm: Force SWIOTLB for secure guests")
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200818221126.391073-1-bauerman@linux.ibm.com

diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
index 85580b30aba482852a06f04a2b257a70f7897e5c..7546402d796af88146163c8e041ace38cade84b8 100644 (file)
--- 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 42e25874f5a8f3bc4096e42f70b7ff57ffb6da6c..ddc32cc1b6cfc9bec836b01511fffa216295afe1 100644 (file)
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -49,6 +49,7 @@
 #include <asm/swiotlb.h>
 #include <asm/rtas.h>
 #include <asm/kasan.h>
+#include <asm/svm.h>
 
 #include <mm/mmu_decl.h>
 
@@ -282,7 +283,10 @@ 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 e6d7a344d9f22112068eae03368e9b9543eab7d9..7b739cc7a8a93efb3774e1ccaee03827d86053de 100644 (file)
--- 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>
@@ -35,6 +36,31 @@ 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))