[PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory
From: Thiago Jung Bauermann <hidden>
Date: 2020-08-18 22:12:25
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 <redacted> --- 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))