Patch "powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory" has been added to the 5.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     powerpc-pseries-svm-allocate-swiotlb-buffer-anywhere.patch
and it can be found in the queue-5.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f5d2008e4ed654938c74316e22bb06f9b757a9d8
Author: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>
Date:   Tue Aug 18 19:11:26 2020 -0300

    powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory
    
    [ Upstream commit eae9eec476d13fad9af6da1f44a054ee02b7b161 ]
    
    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@xxxxxxxxxxxxx>
    Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
    Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20200818221126.391073-1-bauerman@xxxxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
index 85580b30aba48..7546402d796af 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 c2c11eb8dcfca..0f21bcb16405a 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 40c0637203d5b..81085eb8f2255 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))